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INORGANIC SYNTHESES Volume 35

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Board of Directors THOMAS B. RAUCHFUSS, president University of Illinois at Urbana-Champaign DIMITRI COUCOUVANIS University of Michigan MARCETTA Y. DARENSBOURG Texas A&M University JOHN R. SHAPLEY University of Illinois at Urbana-Champaign

Secretary to the Corporation STANTON CHING Connecticut College Future Volumes 36 GREGORY S. GIROLAMI and ALFRED P. SATTELBERGER University of Illinois at Urbana-Champaign and Argonne National Laboratory 37 PHILIP P. POWER University of California at Davis

International Associates MARTIN A. BENNETT Australian National University FAUSTO CALDERAZZO University of Pisa M. L. H. GREEN Oxford University JACK LEWIS Cambridge University RENE POILBLANC University of Toulouse HERBERT W. ROESKY University of Go¨ttingen WARREN R. ROPER University of Auckland F. G. A. STONE Baylor University JAN REEDIJK Leiden University H. VAHRENKAMP University of Freiburg AKIO YAMAMOTO Tokyo Institute of Technology

Editor-in-Chief THOMAS B. RAUCHFUSS University of Illinois at Urbana-Champaign .................................................................

INORGANIC SYNTHESES Volume 35

Copyright Ó 2010 by John Wiley & Sons, Inc. All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission. Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at www.wiley.com.

Library of Congress Catalog Number: 39:23015 ISBN 978-0471-68255-4 Printed in the United States of America 10 9 8 7

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PREFACE This volume presents procedures to compounds that illustrate the scope of modern inorganic and organometallic synthesis. Following the tradition of Inorganic Syntheses, emphasis has been placed on useful compounds and methods. Reflecting my own interests, transition metal derivatives are featured. The largest chapter concerns NacNac complexes. Such complexes represent versatile platforms for a variety of transformations. The NacNac ligands have many desirable features, not the least of which is the scope of their substituted derivatives. The set of procedures was organized by three leaders in this area, Professors Daniel J. Mindiola, Patrick L. Holland, and Timothy H. Warren. In addition to their own contributions, they recruited other colleagues so that the chapter consists of procedures for NacNac complexes of all metals from scandium to zinc. The remaining sections of the book reflect several areas of contemporary activity. Routes are described to a selection of platinum metal reagents that straddle the inorganic and organometallic domains, including some complexes that are of interest in the area of solar energy research. A chapter highlights important complexes from the area of bioorganometallic chemistry. We present an excellent selection of electronically and stereochemically unusual ligands that are easily prepared and adaptable to many metals, for example, the NHCs, bispidines, and Kl€aui’s metalloligand. There is little question that metal-organic frameworks (MOFs) will emerge as an important area of research and possibly applications. We are fortunate to have detailed procedures for important members of this new family of molecule-based materials provided by the leading group in this area. As is our tradition, the volume includes a series of procedures that do not neatly fit into any category, such as salts of the remarkable radical [B12Me12] and the hydrophilic [B12(OH)12]2 . Finally, we include a collection of versatile classical coordination and organometallic complexes. Inorganic Syntheses has benefited from outstanding contributions from across the globe, so I thank these authors and checkers first. Of the many people who helped produce this volume, I wish to recognized my graduate and undergraduate students, several of whom are listed as checkers. My colleagues Greg Girolami and Scott Denmark were sources of advice and encouragement in this venture as they have been throughout my career at Illinois. Finally, I wish to acknowledge the previous editors of Inorganic Syntheses who have inspired me by their example.

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Preface

The first chemistry monograph that I ever bought was Inorganic Syntheses, Volume XIII, edited by F. A. Cotton. I dedicate this volume to the memory of Alan M. Sargeson, a frequent contributor to Inorganic Syntheses, inspired chemist, and gentleman. THOMAS B. RAUCHFUSS University of Illinois at Urbana-Champaign, Urbana, IL

CONTRIBUTORS Debashis Adhikari, Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405 Enzo Alessio, Dipartimento di Scienze Chimiche, Universita` di Trieste, 34127 Trieste, Italy Nicole L. Armanasco, Chemistry M313, School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, WA 6009, Australia Yosra M. Badiei, Department of Chemistry, Georgetown University, Washington, DC 20057-1227 Murray V. Baker, Chemistry M313, School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, WA 6009, Australia Alison G. Barnes, Chemistry M313, School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, WA 6009, Australia Stefan Bernhard, Department of Chemistry, Princeton University, Princeton, NJ 08544 Soledad Betanzos-Lara, Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK Steven M. Bischof, The Scripps Energy Laboratories, The Scripps Research Institute, Jupiter, FL 33458 Karen J. Blackmore, Department of Chemistry, University of California, Irvine, CA 92697 Ioannis Bratsos, Dipartimento di Scienze Chimiche, Universita` di Trieste, 34127 Trieste, Italy David H. Brown, Chemistry M313, School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, WA 6009, Australia Gloria Sanchez Cabrera, Centro de Investigaciones Quı´micas, Universidad Auto´noma del Estado de Hidalgo, Pachuca, Estado de Hidalgo 42184, Mexico vii

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Maria Caporali, Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), 50019 Sesto Fiorentino (Firenze), Italy Chien-Hong Chen, School of Applied Chemistry, Chung Shan Medical University, Taichung, Taiwan Anthony R. Chianese, Department of Chemistry, Yale University, New Haven, CT, 06520-8107 Karen P. Chiang, Department of Chemistry, University of Rochester, Rochester, NY 14627 Young Keun Chung, Department of Chemistry, Seoul National University, Seoul 151-742, Korea Joshua R. Clayton, Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309 Eric D. Cline, Department of Chemistry, Princeton University, Princeton, NJ 08544 Peter Comba, Anorganisch-Chemisches Institut, Universita¨t Heidelberg, D-69120 Heidelberg, Germany Timothy R. Cook, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139-4307 Ryan E. Cowley, Department of Chemistry, University of Rochester, Rochester, NY 14627 Robert H. Crabtree, Department of Chemistry, Yale University, New Haven, CT 06520-8107 Keying Ding, Department of Chemistry, University of Rochester, Rochester, NY 14627 Anders Døssing, Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark Christos Douvris, Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309 Daniel L. DuBois, Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352 Mary Rakowski DuBois, Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352 Lisa Dudek, Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095-1569

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Thomas R. Dugan, Department of Chemistry, University of Rochester, Rochester, NY 14627 Celine Fellay, Institut des Sciences et Inge´nierie Chimiques, Ecole Polytechnique Fe´de´rale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland Matthew G. Fete, Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309 Anne Mette Frey, Department of Chemistry, University of Copenhagen, DK2100 Copenhagen Ø, Denmark Benjamin R. Garrett, Department of Chemistry, University of Illinois at UrbanaChampaign, Urbana, IL 61801 Starla D. Glover, Department of Chemistry and Biochemistry, University of California at San Diego, San Diego, CA 92093 John C. Goeltz, Department of Chemistry and Biochemistry, University of California at San Diego, San Diego, CA 92093 Luca Gonsalvi, Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), 50019 Sesto Fiorentino (Firenze), Italy Abraha Habtemariam, Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK James Hauk, Department of Chemistry and Biochemistry, University of California at San Diego, San Diego, CA 92093 M. Frederick Hawthorne, International Institute of Nano and Molecular Medicine, University of Missouri, Columbia, MO 65211 Paul G. Hayes, Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada T1K 3M4 Valerie J. Hesler, Chemistry M313, School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, WA 6009, Australia Alan F. Heyduk, Department of Chemistry, University of California, Irvine, CA 92697 Yutaka Hitomi, Department of Molecular Chemistry and Biochemistry, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan Patrick L. Holland, Department of Chemistry, University of Rochester, Rochester, NY 14627

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Maik Jakob, Anorganisch-Chemisches Institut, Universita¨t Heidelberg, D-69120 Heidelberg, Germany Satish S. Jalisatgi, International Institute of Nano and Molecular Medicine, University of Missouri, Columbia, MO 65211 Yuuji Kajita, Department of Molecular Chemistry and Biochemistry, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan Marion Kerscher, Anorganisch-Chemisches Institut, Universita¨t Heidelberg, D-69120 Heidelberg, Germany Sang Bok Kim, Department of Chemistry, Brown University, Providence, RI 02912 Benjamin T. King, Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309 Yoshihisa Kishima, Department of Molecular Chemistry and Biochemistry, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan Wolfgang Kla¨ui, Lehrstuhl I: Bioanorganische Chemie und Katalyse, HeinrichHeine-Universita¨t Du¨sseldorf, 40225 Du¨sseldorf, Germany Masahito Kodera, Department of Molecular Chemistry and Biochemistry, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan Elzbieta Kogut, Department of Chemistry, Georgetown University, Washington, DC 20057-1227 Clifford P. Kubiak, Department of Chemistry, University of California at San Diego, San Diego, CA 61801 Peter C. Kunz, Lehrstuhl I: Bioanorganische Chemie und Katalyse, HeinrichHeine-Universita¨t Du¨sseldorf, 40225 Du¨sseldorf, Germany Gabor Laurenczy, Institut des Sciences et Inge´nierie Chimiques, Ecole Polytechnique Fe´de´rale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland Mark W. Lee, Jr., International Institute of Nano and Molecular Medicine, University of Missouri, Columbia, MO 65211 Christopher S. Letko, Department of Chemistry, University of Illinois at UrbanaChampaign, Urbana, IL 61801 Chin Hin Leung, Department of Chemistry, Yale University, New Haven, CT 06520-8107 Wen-Feng Liaw, Department of Chemistry, National Tsing Hua University, Hsinchu 30043, Taiwan

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Simon Lotz, Department of Chemistry, University of Pretoria, Pretoria 0002, South Africa Leonard A. MacAdams, Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 Amanda E. Mack, Department of Chemistry, University of Illinois at UrbanaChampaign, Urbana, IL 61801 Neal D. McDaniel, Department of Chemistry, Princeton University, Princeton, NJ 08544 Marie M. Melzer, Department of Chemistry, Georgetown University, Washington, DC 20057-1227 Josef Michl, Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309; Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 16610 Prague 6, Czech Republic Daniel J. Mindiola, Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405 Tomoyuki Nakagawa, Department of Molecular Chemistry and Biochemistry, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan Andy I. Nguyen, Department of Chemistry, University of California, Irvine, CA 92697 Daniel G. Nocera, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139-4307 Michael R. North, Chemistry M313, School of Biomedical, Biomolecular and Chemical Sciences, The University of Western Australia, Crawley, WA 6009, Australia Yasuhiro Ohki, Department of Chemistry, Graduate School of Science, and Research center for Materials science, Nagoya University, Nagoya 464-8602, Japan Shun Ohta, Department of Chemistry, Graduate School of Science, and Research center for Materials science, Nagoya University, Nagoya 464-8602, Japan Roy A. Periana, The Scripps Energy Laboratories, The Scripps Research Institute, Jupiter, FL 33458 Maurizio Peruzzini, Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), 50019 Sesto Fiorentino (Firenze), Italy

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Warren E. Piers, Department of Chemistry, University of Calgary, Calgary, Alberta, Canada T2N 1N4 Robert D. Pike, Department of Chemistry, College of William and Mary, Williamsburg, VA 23187 Chuleeporn Puttnual, Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716 Udo Radius, Institut fu¨r Anorganische Chemie der Universita¨t Wu¨rzburg, 97074 Wu¨rzburg, Germany Thomas B. Rauchfuss, Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801 Herbert W. Roesky, Institut fu¨r Anorganische Chemie, Universita¨t Go¨ttingen, D-37077 Go¨ttingen, Germany D. Ruckerbauer, Institute of Chemistry, Inorganic Department, Karl-FranzensUniversity, 8010 Graz, Austria Peter J. Sadler, Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK Alexander V. Safronov, International Institute of Nano and Molecular Medicine, University of Missouri, Columbia, MO 65211 Thomas Schaub, BASF SE, 67056 Ludwigshafen, Germany Bryan D. Stubbert, Department of Chemistry, University of Rochester, Rochester, NY 14627 Shouheng Sun, Department of Chemistry, Brown University, Providence, RI 02912 Dwight A. Sweigart, Department of Chemistry, Brown University, Providence, RI 02912 Yoshimitsu Tachi, Department of Molecular Chemistry and Biochemistry, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan Kazuyuki Tatsumi, Department of Chemistry, Graduate School of Science, and Research Center for Materials Science, Nagoya University, Nagoya 464-8602, Japan Thomas S. Teets, Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139-4307 Klaus H. Theopold, Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716

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Leonard L. Tinker, Department of Chemistry, Princeton University, Princeton, NJ 08544 Ba L. Tran, Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405 David J. Tranchemontagne, Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095-1569 Michal Vala´sˇek, Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 16610 Prague 6, Czech Republic Matthew S. Varonka, Department of Chemistry, Georgetown University, Washington, DC 20057-1227 Victoria Volkis, Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309 Adelina M. Voutchkova, Department of Chemistry, Yale University, New Haven, CT 06520-8107 Timothy H. Warren, Department of Chemistry, Georgetown University, Washington, DC 20057-1227 J. W. Wielandt, Institute of Chemistry, Inorganic Department, Karl-FranzensUniversity, 8010 Graz, Austria Stefan Wiese, Department of Chemistry, Georgetown University, Washington, DC 20057-1227 Omar M. Yaghi, Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095-1569 Fabrizio Zanobini, Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), 50019 Sesto Fiorentino (Firenze), Italy Ilya Zharov, Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309 Francisco J. Zuno-Cruz, Centro de Investigaciones Quı´micas, Universidad Auto´noma del Estado de Hidalgo, Pachuca, Estado de Hidalgo 42184, Mexico

DEDICATION This volume is dedicated to the memory of four eminent chemists who made outstanding contributions to inorganic chemistry in general and to Inorganic Syntheses in particular. We mourn their passing, but we celebrate their achievements. ROBERT W. PARRY (EDITOR-IN-CHIEF, VOLUME XII, 1970) Bob was born on October 1, 1917 in Ogden, UT, and died on December 1, 2006 in Salt Lake City, UT, at the age of 89, following a stroke. He received his B.S. degree in soil chemistry from Utah State Agricultural College (now Utah State University) (1940), his M.S. degree in soil chemistry from Cornell University (1942), and his Ph.D. in inorganic coordination chemistry under John C. Bailar, Jr. (Editor-inChief, Inorganic Syntheses, Volume IV, 1953) from the University of Illinois (1946). He served on the chemistry faculties of the University of Michigan (1946–1969) and the University of Utah (Distinguished Professor of Chemistry, 1969–1997). An extraordinary teacher, Bob coauthored the widely used high school text, Chemistry: Experimental Foundations (1970), was senior author of PrenticeHall’s high school chemistry curriculum program (CHEM STUDY), and was coeditor of Prentice-Hall’s paperback series, Foundations of General Chemistry. He mentored more than 60 Ph.D. students and postdoctoral fellows. His honors include first recipient of the ACS Award for Distinguished Service in Inorganic Chemistry (1965), Manufacturing Chemists Award for Excellence in the Teaching of College Chemistry (1972), ACS Award in Chemical Education (1977), Alexander von Humboldt Senior U.S. Scientist Award (1980, 1983), first State of Utah Governor’s Medal in Science and Technology (1987), honorary doctorates from the Utah State University (1985) and the University of Utah (1997), and the ACS’s highest honor, the Priestley Medal (1993). Bob authored more than 150 publications, not only on the boron hydrides but also on gallium, phosphines, and the thermodynamics of chelation. Long active in the ACS, he served as President (1982), member of the Council for more than 45 years and of the Board of Directors (1973–1983), and Associate Editor of the Journal of the American Chemical Society (1966–1968, 1971–1980), and a member of its Editorial Board (1969–1980). He was the founding editor of Inorganic Chemistry (1960–1964) and a member of its Editorial Board (1962–1979) and President of Inorganic Syntheses, Inc. (1969–1972). One of the early leaders of the Gordon Research Conferences, he was a member (1965–1972) xv

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and Chairman (1967–1968) of the GRC Board of Trustees. He was Executive Secretary, Chairman, and Councilor of the American Association for the Advancement of Science between 1980 and 1995, and he held offices in the International Union of Pure and Applied Chemistry between 1965 and 1982. FRANK ALBERT COTTON (EDITOR-IN-CHIEF, VOLUME XIII, 1973) Al, one of the twentieth century’s most prolific, creative, and influential inorganic chemists and chemical educators, was born on April 9, 1930 in Philadelphia, PA, and died following a violent attack on February 20, 2007 in College Station, TX, at the age of 76. He received his primary, secondary, and undergraduate education in Philadelphia, enrolling in the Drexel Institute of Technology, intending to major in chemical engineering. He switched to chemistry and received his B.S. degree from Temple University (1951). He began graduate study at Harvard University, where he joined the research group of future (1973) Nobel chemistry laureate Geoffrey Wilkinson and worked on ferrocene and other metallocenes. After receiving his Ph.D. (1955), he became an Instructor at the Massachusetts Institute of Technology. In 1961, at the age of 3l, he became MIT’s youngest full Professor. As one of the small number of chemists credited with initiating the renaissance of inorganic chemistry that began in the 1950s, Al researched metal carbonyls, ligand field theory, organometallic compounds, phosphine oxide and sulfide complexes, metal complexes with high coordination numbers, protein X-ray crystallography, fluxional organometallic molecules, and application of such physicochemical techniques as infrared and ultraviolet spectroscopies to transition metal complexes. His synthesis and characterization of the [Re2Cl8] (1964) opened a new field of research in multiple metal-metal bonds, metal clusters, and extended solids. He proposed the hapto (h) nomenclature to indicate the structures of p-bonded hydrocarbon ligands. In 1971, Al became Robert A. Welch Professor of Chemistry and shortly thereafter W. T. Doherty-Welch Distinguished Professor of Chemistry at Texas A&M University, where he worked on the synthesis and characterization of compounds with multiple and/or single metal–metal bonds and other unusual species. He and his 118 Ph.D. students and more than 150 postdoctoral fellows from over 30 countries produced more than 1600 publications. He was an ardent and articulate advocate of ‘‘curiosity-driven’’ basic research. Al received many awards from American and foreign societies, including the U.S. National Medal of Science (1982), Robert A. Welch Award (1994), and Israel’s Wolf Prize (2000). His major ACS honors include the Award in Inorganic Chemistry (first recipient, 1962), Award for Distinguished Service in the Advancement of Inorganic Chemistry (1974), Award in Organometallic Chemistry (2001), F. Albert Cotton Medal for Excellence in Chemical Research (first recipient, 1995), George C. Pimentel Award in Chemical Education (2005), and

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the ACS’s highest award, the Priestley Medal (1998). The ACS’s F. Albert Cotton Award in Synthetic Inorganic Chemistry bears his name. He also received 29 honorary doctorates from universities around the world. Al was a prominent scientific educator and textbook author. His Advanced Inorganic Chemistry, coauthored with Geoff Wilkinson, became a standard text. It underwent six editions (1962–1999), sold more than half a million copies, and was translated into 15 foreign languages. From his lecture notes, he wrote Chemical Applications of Group Theory (1963, 1971, 1990). His Chemistry—An Investigative Approach (1973, 1976) was intended for high schools, and his Basic Inorganic Chemistry (1976, 1987, 1995) was an entry-level text. FRED BASOLO (EDITOR-IN-CHIEF, VOLUME XVI, 1976) Fred was born of Italian immigrant parents on February 11, 1920 in Coello, a small coal mining town in southern Illinois, and died on February 27, 2007 in Skokie, IL, at the age of 87. Until he attended school, he spoke the Piedmontese dialect, understanding but speaking little English. The first Coello resident to attend college, he earned his B.Ed, degree from Southern Illinois Normal School (now Southern Illinois University) (1940), intending to teach high school. However, he pursued graduate studies at the University of Illinois on platinum complexes under John C. Bailar, Jr. (Editor-in-Chief, Inorganic Syntheses, Volume IV, 1953), earning his M.S. (1942) and Ph.D. (1943) degrees. After 3 years of war-related research at Rohm and Haas near Philadelphia, PA, he joined the faculty of Northwestern University as Instructor. He rose through the ranks, becoming Charles E. and Emma H. Morrison Professor of Chemistry (1980–1990). He served as Chairman of the Chemistry Department (1969–1972). Fred realized that the work on kinetics and mechanisms of substitution reactions on carbon being investigated by organic chemists could be applied to inorganic coordination compounds such as those of cobalt(III) and platinum(II). He convinced his colleague Ralph G. Pearson to join him in such studies, and the two soon became leaders in the field, and their monograph, Mechanisms of Inorganic Reactions (1958, 1967), became a classic. Their postulation of a SN1CB mechanism for the base hydrolysis of cobalt(III) complexes led to a controversy with Christopher K. Ingold and Ronald S. Nyholm that was resolved in Basolo and Pearson’s favor and garnered them and Northwestern University a global reputation. Fred maintained an international perspective, spending sabbatical leaves with Jannik Bjerrum (1954–1955) and Vincenzo Caglioti (1961–1962). He regarded Italy as a second home and was elected to the Accademia Nazionale dei Lincei (1987), the world’s oldest scientific society. He coauthored Coordination Chemistry (1964, 1986) with former student Ronald C. Johnson. Fred cofounded the Inorganic Gordon Research Conference, which continues today.

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In the ACS, Fred was elected Chairman of the Division of Inorganic Chemistry (1970), a member of its Executive Committee, and President of the society (1983). He received the following ACS honors—Award in Inorganic Chemistry (1964), Award for Distinguished Service in the Advancement of Inorganic Chemistry (1975), George C. Pimentel Award in Chemical Education (1993), and the Priestley Medal, the society’s highest honor (2001). ALAN G. MACDIARMID (EDITOR-IN-CHIEF, VOLUME XVII, 1977) Alan was born on April 14, 1927 in Masterton, New Zealand, and died on February 7, 2007 in Philadelphia, PA, after falling in his home. His youth was spent in poverty (his father lost his job because of the Great Depression), and he left high school at the age of 16 to help support the family. As a part-time student with a lowpaying ‘‘lab boy’’ (janitor) job in the Chemistry Department of Victoria University College at Wellington, he earned his B.Sc. degree (1947) and then became a demonstrator and worked as an assistant. His first publication (in Nature, 1949) dealt with S4N4, a molecule that played a role in his later Nobel-winning research. After graduating with a M.Sc. degree with first class honors (1951), Alan received a Fulbright Fellowship that enabled him to study the rate of exchange in 14 C-tagged metal cyanide complexes at the University of Wisconsin, Madison, from which he received his M.S. (1952) and Ph.D. (1953) degrees. With a New Zealand Shell graduate scholarship, he then studied silicon hydrides under Harry J. Emeleus at Cambridge University, earning his second Ph.D. degree (1955). Following short stints at Queen’s College and the University of St. Andrews, he joined the Department of Chemistry at the University of Pennsylvania, where he spent the remainder of his career, rising through the ranks and becoming Blanchard Professor of Chemistry (1988). In 2002, he became James Von Ehr Distinguished Professor of Science & Technology at the University of Texas, Dallas. After devoting himself to silicon chemistry for two decades, Alan began a fruitful collaboration with his colleague Alan J. Heeger on the conducting polymer, (SN)x, the precursor to which he had studied in Wellington. While a Visiting Professor at Kyoto University, Alan visited the Tokyo Institute of Technology, where Hideki Shirakawa showed him a silvery film of polyacetylene. Shirakawa accepted Alan’s invitation to spend a year with him studying this substance. They discovered that the impurity in polyacetylene served as a dopant and increased its conductivity. By adding bromine to the (CH)x films, they increased the conductivity by many millions of times. The two collaborated with Heeger, and in 2000 the trio shared the Nobel Prize in Chemistry ‘‘for the discovery and development of conductive polymers.’’ Alan wrote more than 600 articles and held 20 patents. His honors include the ACS’s Frederic Stanley Kipping Award in Silicon Chemistry (1971) and Award in the Chemistry of Materials (1999); the Rutherford Medal, the Royal Society of New Zealand’s highest honor (2000); election to the U.S. National Academy of Sciences (2002) and the Order of New Zealand, the country’s

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highest honor (2002); and the fellowship in the Royal Society (2003). His alma mater, Victoria University, awarded him an honorary doctorate (1999), created a chair in physical chemistry in his name (2001), and named an Institute for Advanced Materials and Nanotechnology after him (2003). Institutes named after him include those at Jilin University in China (2001) and the University of Texas, Dallas (2007). STANLEY KIRSCHNER (EDITOR-IN-CHIEF, VOLUME XXIII, 1985) Stan was born on December 17, 1927 in Brooklyn, New York and died on July 16, 2008. Stan attended New York City’s renowned Stuyvesant High School. He had decided on a career in chemistry after his father, a pharmacist, presented him with a chemistry set when he was 11 years old. After graduation Stan enlisted in the U.S. Navy (1944–1945), but then attended Brooklyn College, from which he received his B.S. degree in 1950. Following a brief stint with the Monsanto Chemical Company, he attended Harvard University, where he won a departmental award as the best teaching fellow and from which he received his A.M. degree in 1952. He studied inorganic chemistry at the University of Illinois under John C. Bailar, Jr. (one of the founders of Inorganic Syntheses and Editor-in-Chief of Volume 4, 1953). After receiving his Ph.D. in 1954, Stan joined the faculty of Wayne State University in Detroit, Michigan, where he spent his entire career, rising through the ranks and retiring as Professor Emeritus in 1992. Stan was a longtime Secretary of the Editorial Board of Inorganic Syntheses. His awards and honors include the Wayne State University President’s Award for y Medal of the Czechoslovak Academy Excellence in Teaching (1969), Heyrovsk of Sciences (1978), the ACS Detroit Section’s Distinguished Service Award (1980), the Chemical Manufacturers Award for Excellence in Chemistry Teaching (1984), and the ACS Henry Hill Award and Engineering Society of Detroit’s Gold Award (both in 1995), Stan’s some one hundred articles dealt with the synthesis, structure, stereochemistry, and biological properties of coordination compounds, including the anticancer activity of platinum complexes; optical rotatory dispersion; circular dichroism; the Pfeiffer Effect in metal complexes; inorganic nomenclature; and the application of computer techniques to chemical and information problems. A prominent educator, he edited three books on inorganic and coordination chemistry. Because of his ebullient personality, organizational talent, and interest in foreign languages, Stan held visiting professorships and similar honorary appointments across the globe. Among his many positions, he held positions at University College, London (with Ronald S. Nyholm), University of S~ao Paolo in Brazil, the Centrul de Chimie in Timisoara and Institutul de Chimie in Cluj-Napoca in Romania; the University of Florence, Tohoku University, and both the Technical University and the University of Porto in Portugal. He held honorary membership

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Dedication

in the national societies of most of these countries. Stan was an omnipresent participant at the International Conference on Coordination Chemistry, the longest running conference dedicated to inorganic chemistry. He attended every meeting from 1959 to 2002 and serving as Permanent Secretary and Permanent Secretary Emeritus. GEORGE B. KAUFFMAN California State University, Fresno, CA

NOTICE TO CONTRIBUTORS AND CHECKERS The Inorganic Syntheses series is published to provide all users of inorganic substances with detailed and reliable procedures for the preparation of important and timely compounds. Thus, the series is the concern of the entire scientific community. The Editorial Board hopes that many chemists will share in the responsibility of producing Inorganic Syntheses by offering their advice and assistance in both the formulation and the laboratory evaluation of outstanding syntheses. Help of this kind will be invaluable in achieving excellence and pertinence to current scientific interests. There is no rigid definition of what constitutes a suitable synthesis. The major criterion by which syntheses are judged is the potential value to the scientific community. An ideal synthesis is one that presents a new or revised experimental procedure applicable to a variety of related compounds, at least one of which is critically important in current research. Syntheses of individual compounds that are of interest or importance are, however, also acceptable. Syntheses of compounds that are readily available commercially at reasonable prices are ordinarily not acceptable. Corrections and improvements of syntheses already appearing in Inorganic Syntheses are suitable for inclusion. The Editorial Board lists the following criteria of content for submitted manuscripts. Style should conform with that of previous volumes of Inorganic Syntheses. The introductory section should include a concise and critical summary of the available procedures for synthesis of the product in question. It should also include an estimate of the time required for the synthesis, an indication of the importance and utility of the product, and an admonition if any potential hazards are associated with the procedure. The Procedure section should present detailed and unambiguous laboratory directions and be written so that it anticipates possible mistakes and misunderstandings on the part of the person who attempts to duplicate the procedure. Unusual equipment or procedure should be clearly described. Line drawings should be included when they can be helpful. Safety measures should be stated clearly. Sources of unusual starting materials must be given, and, if possible, minimal standards of purity of reagents and solvents should be stated. The scale should be reasonable for normal laboratory operation, and problems involved in scaling the procedure either up or down should be discussed. The criteria for judging the purity of the final product should be delineated clearly. The Properties section should supply and discuss those physical and chemical characteristics that are relevant to judging the purity of the product and to xxi

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Notice to Contributors and Checkers

permitting its handling and use in an intelligent manner. Under References, pertinent literature citations should be listed in order. The style sheet is available at www.inorgsynth.com. The Editorial Board determines whether submitted syntheses meet the general specifications outlined above. Every procedure will be checked in an independent laboratory, and publication is contingent on satisfactory duplication of the syntheses. For online access to information and requirements, see www.inorgsynth.com. Each manuscript should be submitted to the Secretary of the Editorial Board, Professor Stanton Ching, [email protected] The manuscript should be typewritten in English. Nomenclature should be consistent and should follow the recommendations presented in Nomenclature of Inorganic Chemistry, 2nd ed., Butterworths & Co, London, 1970 and in Pure and Applied Chemistry, Volume 28, No. 1 (1971). Abbreviations should conform to those used in publications of the American Chemical Society, particularly Inorganic Chemistry. Chemists willing to check syntheses should contact the editor of a future volume or make this information known to Professor Ching.

TOXIC SUBSTANCES AND LABORATORY HAZARDS Chemicals and chemistry are by their very nature hazardous. The obvious hazards in the syntheses reported in this volume are delineated, where appropriate, in the experimental procedure. It is impossible, however, to foresee every eventuality, such as a new biological effect of a common laboratory reagent. As a consequence, all chemicals used and all reactions described in this volume should be viewed as potentially hazardous. Care should be taken to avoid inhalation or other physical contact with reagents and solvents used in this volume. In addition, particular attention should be paid to avoiding sparks, open flames, or other potential sources that could set fire to combustible vapors or gases. The following sources are especially recommended for guidance: NIOSH Pocket Guide to Chemical Hazards (U.S. by the National Institute for Occupational Safety and Health) is available free at http://www.cdc.gov/niosh/ npg/ and can be purchased inexpensively in paperback format. It contains information and data for 677 common compounds and classes of compounds. Organic Syntheses, which is freely available online (http://www.orgsyn.org/), has a concise but useful section ‘‘Handling Hazardous Chemicals.’’ Prudent Practices in the Laboratory: Handling and Disposal of Chemicals (National Academy Press, 1995, ISBN 0-309-05229-7). This classic book presents guidelines for laboratory practices. The contents can be read freely online at http:// www.nap.edu/catalog.php?record_id=4911. Purification of Laboratory Chemicals by D. D. Perrin, W. L. F. Armarego, and D. R. Perrin (Pergamon, 2009, ISBN 978-1-85617-567-8) is the standard reference for the purification of reagents and solvents. Special attention should be paid to the purification and storage of ethers.

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CONTENTS Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . Contributors . . . . . . . . . . . . . . . . . . . . . . . Dedication . . . . . . . . . . . . . . . . . . . . . . . . Notice to Contributors and Checkers . . . . . Toxic Substances and Laboratory Hazards. Chapter One

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COMPLEXES OF BULKY b-DIKETIMINATE LIGANDS

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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2. b-Diketiminate Precursors HLMe,Me3 and TlLMe,Me3 (LMe,Me3 ¼ 2,4-Bis-(Mesitylimido)Pentyl) . . . . . . . . . . . . . 4 A. 2,4-Bis-(Mesitylimido)Pentane (HLMe,Me3) . . . . . . . . . . . . . . . . . . 5 B. Thallium 2,4-Bis-(Mesitylimido)Pentyl (TlLMe,Me3) . . . . . . . . . . . . 6 3. b-Diketiminate Precursors LMe,iPr2H, [LMe,iPr2Li]x, and [LtBu,iPr2K]x (LMe,iPr2¼2,4-Bis-(2,6Diisopropylphenylimido)Pentyl; LtBu,iPr2¼2,2,6,6Tetramethyl-3,5-Bis-(2,6-Diisopropylphenylimido)Heptyl) A. 2,4-Bis-(2,6-Diisopropylphenylimido)Pentane (LMe,iPr2H) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. Lithium 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl ([LMe,iPr2Li]x). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. Potassium 2,2,6,6-Tetramethyl-3,5-Bis-(2,6Diisopropylphenylimido)Heptyl ([LtBu,iPr2K]x). . . . . . .

......... 8 ......... 9 . . . . . . . . 10 . . . . . . . . 11

4. b-Diketiminate Precursors LtBu,iPr2H and LtBu,iPr2Li(THF) (LtBu,iPr2¼2,2,6,6-Tetramethyl-3,5Bis-(2,6-Diisopropylphenylimido)Heptyl) . . . . . . . . . . . . . . . . A. N-Pivaloyl-2,6-Diisopropylanilide (DIPPNHC(O)tBu) . . . . B. DIPPN¼C(Cl)tBu. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. DIPPN¼C(Me)tBu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D. 2,2,6,6-Tetramethyl-3,5-Bis-(2,6-Diisopropylphenylimido) Heptane ([DIPPN¼C(tBu)]2CH2, LtBu,iPrH) . . . . . . . . . . . .

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E. Lithium 2,2,6,6-Tetramethyl-3,5-Bis(2,6-Diisopropylphenylimido)Heptyl (LtBu,iPr2Li, THF Adduct) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5. Scandium Trichloride Tris(Tetrahydrofuran) and b-Diketiminate-Supported Scandium Chloride Complexes. . . . A. Scandium Trichloride Tris(Tetrahydrofuran), ScCl3(THF)3 . B. Scandium 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl Dichloride Tetrahydrofuran, (LMe,iPr2)ScCl2(THF) . . . . . . . C. Scandium 2,2,6,6-Tetramethyl-3,5-Bis-(2,6Diisopropylphenylimido)Heptyl Dichloride, (LtBu,iPr2)ScCl2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. b-Diketiminate-Supported Titanium and Vanadium Dichloride Complexes . . . . . . . . . . . . . . . . . . . . . . . . A. Synthesis of (LMe,iPr2)TiCl2(THF) . . . . . . . . . . . . . B. Synthesis of (LtBu,iPr2)TiCl2 . . . . . . . . . . . . . . . . . C. Synthesis of (LMe,iPr2)VCl2 . . . . . . . . . . . . . . . . . .

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25 25 27 28

7. b-Diketiminate-Supported Vanadium and Chromium Chloride Complexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 A. Synthesis of LMe,Me2VCl2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 B. Synthesis of LMe,Me2CrCl2(THF)2 . . . . . . . . . . . . . . . . . . . . . . . . 32 8. b-Diketiminate-Supported Manganese and Zinc Complexes. A. LMe,iPr2MnI(THF). . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. The THF-Free Dimer (LMe,iPr2MnI)2 . . . . . . . . . . . . . . . C. LMe,iPr2ZnCl2Li(OEt2)2 . . . . . . . . . . . . . . . . . . . . . . . . .

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34 34 35 36

9. Iron 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl Chloride (LMe,iPr2FeCl) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10. Iron 2,2,6,6-Tetramethyl-3,5-Bis-(2,6Diisopropylphenylimido)Heptyl Chloride (LtBu,iPr2FeCl) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 11. Cobalt 2,2,6,6-Tetramethyl-3,5-Bis-(2,6-Diisopropylphenylimido) Heptyl Chloride (LtBu,iPr2CoCl) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 12. b-Diketiminate-Supported Nickel(II) and Nickel(I) Complexes of LMe,Me3 (LMe,Me3¼2,4-Bis-(Mesitylimido)Pentyl) . . . . 45 A. LMe,Me3NiI(2,4-Lutidine) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 B. LMe,Me3Ni(2,4-Lutidine) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Contents

xxvii

13. Nickel 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl Chloride Dimer, [LMe,iPr2Ni(m-Cl)]2 . . . . . . . . . . . . . . . . . . . . . . . . . 48 14. Bis[Copper 2,4-Bis-(2,4,6-Trimethylphenylimido)Pentyl] Toluene, (LMe,Me3Cu)2(m-h2:h2-C7H8) . . . . . . . . . . . . . . . . . . . . . . . 50 A. Copper tert-Butoxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 B. Bis[Copper 2,4-Bis-(2,4,6Trimethylphenylimido)pentyl] Toluene . . . . . . . . . . . . . . . . . . . . 52 15. Copper 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl Chloride (LMe,iPr2CuCl) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Chapter Two

BORON CLUSTER COMPOUNDS

16. Salts of Dodecamethylcarba-closo-Dodecaborate( ) Anion, CB11Me12 , and the Radical Dodecamethylcarbacloso-Dodecaboranyl, CB11Me12 . . . . . . . . . . . . . . . . . . . A. Cesium 1-Methylcarba-closo-Dodecaborate( ), Cs[1-Me-CB11H11] . . . . . . . . . . . . . . . . . . . . . . . . . . . B. Cesium, Tetramethylammonium, and Lithium Dodecamethylcarba-closo-Dodecaborates( ), Cs[CB11Me12], [NMe4][CB11Me12], and Li[CB11Me12] C. Dodecamethylcarba-closo-Dodecaboranyl Radical, CB11Me12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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17. Cesium Dodecahydroxy-closo-Dodecaborate, Cs2[B12(OH)12] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Chapter Three COORDINATION COMPOUNDS

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18. Pentaaquanitrosylchromium Sulfate . . . . . . . . . . . . . . . . . . . . . . . . . 67 A. Pentaaquanitrosylchromium Sulfate . . . . . . . . . . . . . . . . . . . . . . 68 19. The Tetradentate Bispidine Ligand Dimethyl-(3,7-Dimethyl9-oxo-2,4-bis(2-pyridyl)-3,7-Diazabicyclo[3.3.1]nonane)-1, 5-dicarboxylate and Its Copper(ll) Complex . . . . . . . . . . . . . A. Piperidone (pI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. Bispidone 3,7-dimethyl-9-oxo-2,4-bis(2-pyridyl-3,7diazabicyclo[3.3.1]nonane-1,5-dicarboxylate dimethylester (L) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. Copper(II) Bispidone Chloride (CuLCl) . . . . . . . . . . . . .

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20. Tris(2-Picolinyl)Methane and Its Copper(I) Complex . A. Bis(2-Picolinyl)Methane . . . . . . . . . . . . . . . . . . . B. Tris(2-Picolinyl)Methane . . . . . . . . . . . . . . . . . . . C. Copper(I) (Tris(2-Picolinyl)Methane)Acetonitrile Hexafluorophosphate . . . . . . . . . . . . . . . . . . . . . . Chapter Four

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CARBENE LIGANDS AND COMPLEXES

21. 1,3-Dialkyl-Imidazole-2-Ylidenes . . . . . . . . . . . . . . . . . . . A. 1,3-DI-n-Propyl-Imidazolium Chloride ( n Pr2 ImHCl) and 1,3-Diisopropyl-Imidazolium Chloride ( i Pr2 ImHCl) B. 1,3-Dimethyl-Imidazolium Iodide (Me2ImHI) and 1-Methyl-3-Isopropyl-Imidazolium Iodide (MeiPrImHI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. 1,3-DI-n-Propyl-Imidazol-2-Ylidene (n Pr2 Im) and 1,3-Diisopropyl-Imidazol-2-Ylidene ( i Pr2 Im) . . . . . D. 1,3-Dimethyl-Imidazol-2-Ylidene (Me2Im) and 1-Methyl-3-Isopropyl-Imidazol-2-Ylidene (MeiPrIm). . .

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22. A Chelating Rhodium N-Heterocyclic Carbene Complex by Transmetallation from a Silver–NHC Intermediate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 A. Methylenebis(N-(t-Butyl)Imidazolium) Bromide . . . . . . . . . . . . . 84 B. {Methylenebis(N-(t-Butyl)Imidazol-2-Ylidene)} (1,5-Cyclooctadiene)Rhodium(I) Hexafluorophosphate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 23. Rhodium and Iridium N-Heterocyclic Carbene Complexes from Imidazolium Carboxylates . . . . . . . . . . . . A. N,N0 -Dimethylimidazolium-2-Carboxylate. . . . . . . . . . . B. Chloro(1,5-Cyclooctadiene)(1,3-Dimethylimidazolium2-Ylidene) Rhodium(I) . . . . . . . . . . . . . . . . . . . . . . . . . C. (h4-1,5-Cyclooctadiene)(Bis-1,3-Dimethylimidazole2-Ylidene)Iridium(I) Hexafluorophosphate. . . . . . . . . . . Chapter Five

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FUNCTIONAL LIGANDS AND COMPLEXES

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24. N-tert-Butyl ortho-Aminophenol, ortho-Iminoquinone, and a Zirconium(IV) bis(Aminophenolate) Complex . . . . . . . . . . . . . . . . 92 A. 2,4-Di-tert-Butyl-6-(tert-Butylamino)Phenol . . . . . . . . . . . . . . . . . . 93 B. 2,4-Di-tert-Butyl-6-(tert-Butylimino)Quinone . . . . . . . . . . . . . . . 94 C. ZrIV(ap)2(THF)2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

Contents

25. Synthesis of the Water-Soluble Bidentate (P, N) Ligand PTN(Me) (PTN(Me) ¼ 7-Phospha-3-methyl-1,3,5triazabicyclo[3.3.1]nonane) . . . . . . . . . . . . . . . . . . . . . . . . A. Dehydration of Tetrakis(Hydroxymethyl)Phosphonium Chloride, THPC, [P(CH2OH)4]Cl . . . . . . . . . . . . . . . . . B. Tris(Hydroxymethyl)Phosphine, P(CH2OH)3 . . . . . . . . . C. Tris(Hydroxymethyl)Methyl Phosphonium Iodide, [PCH3(CH2OH)3]I . . . . . . . . . . . . . . . . . . . . . . . . . . . . D. 7-Methyl-1,3,5-Triaza-7-Phosphoniaadamantane Iodide . E. 7-Phospha-3-Methyl-1,3,5-Triazabicyclo[3.3.1]nonane, PTN(Me) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26. Synthesis of Metal-Organic Frameworks: MOF-5 and MOF-177 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. MOF-5: Zn4O(Terephthalate)3 (Solvothermal) . . . . B. MOF-5: Zn4O(Terephthalate)3 (Room Temperature). C. MOF-177: Zn4O(1,3,5-Benzenetribenzoate)2 (Room Temperature) . . . . . . . . . . . . . . . . . . . . . . . Chapter Six

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ORGANOMETALLIC REAGENTS

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27. Tricarbonyl 1,3,5-Trimethyl-1,3,5-Triazacyclohexane Complexes of Chromium(0), Molybdenum(0), and Tungsten(0) [M(CO)3(Me3TACH) (M ¼ Cr, Mo, W)] . . . . . . . . . . . . . . . . . . . . . . A. Tricarbonyl(1,3,5-Trimethyl-1,3,5-Triazacyclohexane) Chromium(0), fac-Cr(CO)3(Me3TACH) . . . . . . . . . . . . . . . . . . . B. Tricarbonyl(1,3,5-Trimethyl-1,3,5-Triazacyclohexane) Molybdenum(0), fac-Mo(CO)3(Me3TACH) . . . . . . . . . . . . . . . . . C. Tricarbonyl(1,3,5-Trimethyl-1,3,5-Triazacyclohexane) Tungsten(0), fac-W(CO)3(Me3TACH) . . . . . . . . . . . . . . . . . . . . . 28. Manganese Tricarbonyl Transfer (MTT) Agents . . . . . . . A. Acenaphthene(Tricarbonyl)Manganese(I) . . . . . . . . . B. Naphthalene(Tricarbonyl)Manganese(I) . . . . . . . . . . C. Synthesis of h6-N,N-Dimethylaniline(Tricarbonyl)Manganese(I) Tetrafluoroborate, [Mn(h6-C6H5NMe2) (CO)3]BF4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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29. Bis(1,5-Cyclooctadiene)Nickel(0) . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Hexakis(Acetylacetonato)Trinickel(II). . . . . . . . . . . . . . . . . . . . B. Di(n-Butyl)Magnesium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. Bis(1,5-Cyclooctadiene)Nickel(0) . . . . . . . . . . . . . . . . . . . . . . .

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30. Sodium (h5-Cyclopentadienyl)Tris(Dimethylphosphito-P) Cobaltate(III), Na[(C5H5)Co{P(O)(OMe)2}3] . . . . . . . . . . . . . . . . . 125 A. [Co((C5H5)Co{P(O)(OMe)2}3)2], Co(LOMe)2 . . . . . . . . . . . . . . . . 126 B. Na[(C5H5)Co{P(O)(OMe)2}3], NaLOMe . . . . . . . . . . . . . . . . . . . 126 Chapter Seven

BIO-INSPIRED IRON AND NICKEL COMPLEXES

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31. Iron–Cyanocarbonyl Complexes [PPN][Fe(CO)4(CN)] and [PPN][FeBr(CO)3(CN)2] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129 A. Bis(Triphenylphosphoranylidene)Ammonium Tetracarbonylcyanoferrate(0), [PPN][Fe(CO)4(CN)] . . . . . . . . . . . 130 B. Bis(Triphenylphosphoranylidene)Ammonium Bromotricarbonylcyanoferrate(II), [PPN][FeIIBr(CO)3(CN)2] . . . 131 32. Nickel Complexes of Bis(Diethylphosphinomethyl) Methylamine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Bis(Diethylphosphinomethyl)Methylamine . . . . . . . . . . . . . . . . B. Bis(Bis(Diethylphosphinomethyl)Methylamine) Nickel(0), Ni(PNP)2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. Hydridobis(PNP)Nickel(II) Hexafluorophosphate . . . . . . . . . . . . D. Bis(PNP)Nickel(II) Tetrafluoroborate . . . . . . . . . . . . . . . . . . . . 33. Monomeric Iron(II) Complexes Having Two Sterically Hindered Arylthiolates. . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Bis[Bis(Trimethylsilyl)Amido]Iron(II) . . . . . . . . . . . . . B. 2,6-Di(Mesityl)Benzenethiol . . . . . . . . . . . . . . . . . . . . . C. Fe[SC6H3-2,6-(Mesityl)2]2 (Mesityl ¼ C6H2-2,4,6-Me3). 34 (1,3-Propanedithiolato)-Hexacarbonyldiiron and Cyanide Derivatives . . . . . . . . . . . . . . . . . . . . . . A. (1,3-Propanedithiolato)Hexacarbonyldiiron . . . . . . B. Tetraethylammonium (1,3-Propanedithiolato) Tetracarbonyldiiron Dicyanide . . . . . . . . . . . . . . . C. Tetraethylammonium (1,3-Propanedithiolato) Pentacarbonyldiiron Cyanide . . . . . . . . . . . . . . . . Chapter Eight

RUTHENIUM COMPLEXES

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137 138 140 141

. . . . . . . . . . 143 . . . . . . . . . . 144 . . . . . . . . . . 145 . . . . . . . . . . 146 148

35. Ruthenium(II)-Chlorido Complexes of Dimethylsulfoxide . . . . . . . . 148 A. cis-Dichloridotetrakis(dimethylsulfoxide)ruthenium(II) . . . . . . . 150 B. trans-Dichloridotetrakis(dimethylsulfoxide)ruthenium(II) . . . . . 151

Contents

xxxi

36. Synthesis of Chloride-Free Ruthenium(II) Hexaaqua Tosylate, [Ru(H2O)6]tos2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152 37. Basic Ruthenium Acetate and Mixed Valence Derivatives . . . A. Tri(Aquo)-m3-Oxo-Hexakis(m-Acetate)Triruthenium Acetate, [Ru3(m3-O)(m-OAc)6(H2O)3]OAc . . . . . . . . . . . . B. Tri(Pyridine)-m3-Oxo-Hexakis(m-Acetate)Triruthenium, Ru3(m3-O)(m-OAc)6(py)3 . . . . . . . . . . . . . . . . . . . . . . . . . C. Di(Aquo)-m3-Oxo-Hexakis(m-Acetate)CarbonylTriruthenium(II, III, III), Ru3(m3-O)(m-OAc)6(CO)(H2O)2 .

. . . . . 156 . . . . . 156 . . . . . 157 . . . . . 158

38. Di-m-Chloro(Ethylbenzoate)Diruthenium(II), [(h6-etb)RuCl2]2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 A. Ethyl-1,4-Cyclohexadiene-3-Carboxylate . . . . . . . . . . . . . . . . . 161 B. Chloro(Ethylbenzoate)Diruthenium(II), [(h6-etb)RuCl2]2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 Chapter Nine

IRIDIUM COMPLEXES

164

39. The Diphosphine tfepma and its Diiridium Complex Ir20,II(tfepma)3Cl2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Bis(dichlorophosphino)methylamine . . . . . . . . . . . . . . . . . . . . . B. Bis(bis(trifluoroethoxy)phosphino)methylamine (tfepma) . . . . . . C. Ir20,II(tfepma)3Cl2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40. Heteroleptic Cyclometalated Iridium(III) Complexes . . . . . . A. Di-m-chlorotetrakis[2-(2-pyridinyl-N)phenyl-C] diiridium(III), [Ir(ppy)2Cl]2 . . . . . . . . . . . . . . . . . . . . . . B. (2,20 -bipyridine-kN1, kN10 )Bis[2-(2-pyridinyl-kN) phenyl-kC]–iridium(III) hexafluorophosphate, [Ir(ppy)2bpy]PF6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. 2-(4-Fluorophenyl)-5-methyl-pyridine, F–mppy . . . . . . . . D. Di-m-Chlorotetrakis[5-Fluoro-2-(5-Methyl-2-Pyridinyl-N) Phenyl-C]Diiridium(III), [Ir(F–mppy)2Cl]2 . . . . . . . . . . .

164 165 166 167

. . . . . 168 . . . . . 169

. . . . . 170 . . . . . 171 . . . . . 171

41. Oxygen and Carbon Bound Acetylacetonato Iridium(III) Complexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 A. trans-Bis-(Acetylacetonato-O,O)(Acetylacetonato-C3)Aquo Iridium(III), (acac-O,O)2Ir(acac-C3)(H2O). . . . . . . . . . . . . . . . . 174 B. Bis-(m-Acetylacetonato-O,O,C3)-Bis-(AcetylacetonatoO,O)-Bis-(Acetylacetonato-C3) Diiridium(III), [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2 . . . . . . . . . . . . . . . . . 175

xxxii

Contents

C. trans-Bis-(Acetylacetonato-O,O)(Acetylacetonato-C3) Pyridine Iridium(III), (acac-O,O)2Ir(acac-C3)Pyridine . . . . . . . . 176 Contributor Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 Formula Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

Chapter One

COMPLEXES OF BULKY b-DIKETIMINATE LIGANDS 1. INTRODUCTION by DANIEL J. MINDIOLA, PATRICK L. HOLLAND,† and TIMOTHY H. WARRENz

In the past decade, b-diketiminates1 have experienced a dramatic renaissance.2 These scaffolds are structurally analogous to the ubiquitous acac (acetylacetonate) ligand, forming a six-membered chelate ring with nitrogen atoms in place of the oxygen atoms of acac. Like the popular cyclopentadienyl ligand, the monoanionic b-diketiminate ligand forms complexes with a wide variety of main-group and d-block metals, lanthanides, and actinides.2 Moreover, b-diketiminates often serve as a robust framework for supporting metal-containing functional groups owing to their relatively strong donating properties and chelating nature. As such, b-diketiminate complexes rarely suffer from decomplexation pathways that often plague monodentate ligands such as amides, amines, and neutral diimines. Although b-diketiminates typically bind in a bidentate fashion, the delocalization of charge about the NCCCN ring renders it possible for metals to coordinate to the face of the ligand with hapticities up to h5. In such cases, the coordination geometry is highly dependent on both the metal and ligand substituents.2 *

Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405. † Department of Chemistry, University of Rochester, Rochester, NY 14627. z Department of Chemistry, Georgetown University, Washington, DC 20057-1227. Inorganic Syntheses, Volume 35, edited by Thomas B. Rauchfuss Copyright Ó 2010 John Wiley & Sons, Inc. 1

2

Complexes of Bulky b-Diketiminate Ligands

The availability of straightforward, multigram syntheses for many classes of b-diketiminates has generated widespread popularity of the ligand for coordination and organometallic chemistry. Prototypical b-diketimines with N-aryl substituents can be synthesized in one step from commercially available anilines and diones through simple condensation reactions.1,3 b-Diketiminate ligands with aliphatic nitrogen substituents can also be prepared by related condensation routes, but often require harsh reagents such as oxonium salts for complete diimine formation.4 More sterically encumbered derivatives possessing tert-butyl groups on the b-carbons of the NCCCN backbone require a multistep, but high-yielding, synthesis (described herein).5 Other variants of the b-diketiminate scaffold have been recently discussed in a comprehensive review.2 This chapter focuses on the N-aryl b-diketiminates, which have a high degree of modularity of the R and R0 positions of the NCCCN backbone, and of the N-aryl ortho substituents (R00 and R000 ) (Fig. 1, left). Steric and electronic factors can easily be fine-tuned via the R, R0 , and R00 groups. For instance, the steric demands of the coordination wedge in b-diketiminatometal complexes (Fig. 1, right) can be modified by judicious choice of R and R00 substituents, while the electronic properties of the ligand are influenced predominantly by the backbone substituents R0 , and to a lesser extent, R. In this chapter, we describe complexes of four different b-diketiminate ligands using a notation that specifies R and R00 /R000 substituents (R0 ¼ H in all syntheses described here). Thus, LMe,Me2 indicates R ¼ R00 ¼ Me and R000 ¼ H; LMe,Me3 indicates R ¼ R00 ¼ R000 ¼ Me; LMe,iPr2 indicates R ¼ Me, R00 ¼ iPr, and R000 ¼ H; and LtBu,iPr2 indicates R ¼ tBu, R00 ¼ iPr, and R000 ¼ H. An important application for b-diketiminates is the generation of low-coordinate metal complexes. This propensity for stabilizing complexes with low coordination numbers has proven particularly useful for the isolation of systems with unprecedented oxidation states, especially low oxidation state main-group species.6 Such complexes often serve as precursors for group-transfer reactions to

Figure 1. Left: General structure of a b-diketiminate ligand with aryl substituted nitrogen groups. Right: The coordination wedge of a metal complex with LMe,iPr2 (R ¼ Me, R0 ¼ H, R00 ¼ iPr, R000 ¼ H), depicting how the R00 groups block the axial sites of the metal atom (shown in black).

1. Introduction

3

afford reactive, metal-bound functional groups. Low-coordinate b-diketiminate complexes also play host to a variety of reactive functionalities including hydrides,7 alkyls,2,8 alkylidenes/carbenes,9,10 alkylidynes,11 imides/nitrenes and nitrides,12–15 and phosphinidenes.9,16 Many of these functionalities find application in catalysis such as copolymerization,17 ring-opening polymerization,18 alkene and alkyne polymerization,5,8,11,19 olefin metathesis,20 intramolecular hydroamination,21 carboamination,22 intermolecular hydrophosphination,16c carbene and nitrene group transfer,9,10 and hydrodefluorination.23 In biomimetic chemistry, b-diketiminate ligands have been used in type 1 ‘‘blue’’ copper sites,24 the study of dioxygen activation by cobalt10a and copper,25 the binding of nitric oxide by nickel,26 and the binding of nitrogenase substrates to iron.27 In this chapter we collect representative procedures for the preparation of the most popular family of N-aryl b-diketiminate ligands, and of alkali metal and thallium salts that are especially useful precursors to transition metal complexes. We then describe the preparation of a series of useful b-diketiminato metal complexes with 3d transition metals from Sc to Zn, each of which serves as a template for further elaboration. References 1. S. G. McGeachin, Can. J. Chem. 46, 1903 (1968). 2. L. Bourget-Merle, M. F. Lappert, and J. S. Severn, Chem. Rev. 102, 3031 (2002). 3. M. Stender, R. J. Wright, B. E. Eichler, J. Prust, M. M. Olmstead, H. W. Roesky, and P. P. Power, Dalton Trans. 3465 (2001). 4. (a) N. Kuhn, H. Lanfermann, and P. Schmitz, Liebigs Ann. Chem. 8, 727 (1987). (b) N. Kuhn, J. Fahl, S. Fuchs, M. Steimann, G. Henkel, and A. H. Maulitz, Z. Anorg. Allg. Chem. 2108 (1999). 5. P. H. M. Budzelaar, A. B. van Oort, and A. G. Orpen, Eur. J. Inorg. Chem. 1485 (1998). 6. (a) H. W. Roesky, S. Singh, V. Jancik, and V. Chandrasekhar, Acc. Chem. Res. 37, 969 (2004). (b) H. W. Roesky and S. S. Kumar, Chem. Commun. 4027 (2005). (c) N. J. Hardman, C. Cui, H. W. Roesky, W. H. Fink, and P. P. Power, Angew. Chem., Int. Ed. 40, 2172 (2001). 7. Y. Yu, A. R. Sadique, J. M. Smith, T. R. Dugan, R. E. Cowley, W. W. Brennessel, C. J. Flaschenriem, E. Bill, T. R. Cundari, and P. L. Holland, J. Am. Chem. Soc. 130, 6624 (2008). 8. W. E. Piers and D. J. H. Emslie, Coord. Chem. Rev. 131, 233 (2002). 9. D. J. Mindiola, Acc. Chem. Res. 39, 813 (2006). 10. (a) X. Dai, P. Kapoor, and T. H. Warren, J. Am. Chem. Soc. 126, 4798 (2004). (b) L. D. Amisial, X. Dai, R. A. Kinney, A. K. Krishnaswamy, and T. H. Warren, Inorg. Chem. 43, 6537 (2004). 11. F. Basuli, B. C. Bailey, D. Brown, J. Tomaszewski, J. C. Huffman, M.-H. Baik, and D. J. Mindiola, J. Am. Chem. Soc. 126, 10506 (2004). 12. A. R. Fout, U. J. Kilgore, and D. J. Mindiola, Chem. Eur. J. 13, 9428 (2007). 13. (a) E. Kogut, H. L. Wiencko, L. Zhang, D. E. Cordeau, and T. H. Warren, J. Am. Chem. Soc. 127, 11248 (2005). (b) Y. M. Badiei, A. Krishnaswamy, M. M. Melzer, and T. H. Warren, J. Am. Chem. Soc. 128, 15056 (2006). (c) X. Dai, P. Kapoor, and T. H. Warren, J. Am. Chem. Soc. 126, 4798 (2004). 14. G. Bai and D. W. Stephan, Angew. Chem., Int. Ed. 46, 1856 (2007). 15. (a) N. A. Eckert, S. Vaddadi, S. Stoian, R. J. Lachicotte, T. R. Cundari, and P. L. Holland, Angew. Chem., Int. Ed. 45, 6868 (2006). (b) B. L. Tran, M. Pink, X. Gao, H. Park, and D. J. Mindiola, J. Am. Chem. Soc. 132, 1458 (2010).

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16. (a) F. Basuli, J. Tomaszewski, J. C. Huffman, and D. J. Mindiola, J. Am. Chem. Soc. 125, 10170 (2003). (b) F. Basuli, B. C. Bailey, J. C. Huffman, M.-H. Baik, and D. J. Mindiola, J. Am. Chem. Soc. 126, 1924 (2004). (c) G. Zhao, F. Basuli, U. J. Kilgore, H. Fan, H. Aneetha, J. C. Huffman, G. Wu, and D. J. Mindiola, J. Am. Chem. Soc. 128, 13575 (2006). 17. (a) S. D. Allen, D. R. Moore, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 124, 14284 (2002). (b) M. Cheng, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 120, 11018 (1998). (c) C. M. Byrne, S. D. Allen, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 126, 11404 (2004). (d) R. C. Jeske, A. M. DiCiccio, and G. W. Coates, J. Am. Chem. Soc. 129, 11330 (2007). (e) C. T. Cohen, T. Chu, and G. W. Coates, J. Am. Chem. Soc. 127, 10869 (2005). (f) D. R. Moore, M. Cheng, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 125, 11911 (2003). (g) M. Cheng, D. R. Moore, J. J. Reczek, B. M. Chamberlain, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 123, 8738 (2001). 18. (a) M. Cheng, A. B. Attygalle, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 121, 11583 (1999). (b) L. R. Rieth, D. R. Moore, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 124, 15239 (2002). (c) B. M. Chamberlain, M. Cheng, D. R. Moore, T. M. Ovitt, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 123, 3229 (2001). 19. P. G. Hayes, W. E. Piers, and R. McDonald, J. Am. Chem. Soc. 124, 2132 (2002). 20. Z. J. Tonzetich, A. J. Jiang, R. R. Schrock, and P. Muller, Organometallics 26, 3771 (2007). 21. (a) F. Lauterwasser, P. G. Hayes, S. Brase, W. E. Piers, and L. L. Schafer, Organometallics 23, 2234 (2004). (b) M. R. Crimmin, I. J. Casely, and M. S. Hill, J. Am. Chem. Soc. 127, 2042 (2005). 22. (a) F. Basuli, H. Aneetha, J. C. Huffman, and D. J. Mindiola, J. Am. Chem. Soc. 127, 17992 (2005). (b) H. Aneetha, F. Basuli, J. Bollinger, J. C. Huffman, and D. J. Mindiola, Organometallics 25, 2725 (2006). 23. J. Vela, J. M. Smith, Y. Yu, N. A. Ketterer, C. J. Flaschenriem, R. J. Lachicotte, and P. L. Holland, J. Am. Chem. Soc. 127, 7857 (2005). 24. (a) P. L. Holland and W. B. Tolman, J. Am. Chem. Soc. 121, 7270 (1999). (b) P. L. Holland and W. B. Tolman, J. Am. Chem. Soc. 122, 6331 (2000). (c) D. W. Randall, S. D. George, P. L. Holland, B. Hedman, K. O. Hodgson, W. B. Tolman, and E. I. Solomon, J. Am. Chem. Soc. 122, 11632 (2000). 25. (a) C. J. Cramer and W. B. Tolman, Acc. Chem. Res. 40, 601 (2007). (b) X. L. Dai and T. H. Warren, Chem. Commun. 1998 (2001). 26. S. C. Puiu and T. H. Warren, Organometallics 22, 3974 (2003). 27. (a) J. Vela, S. Stoian, C. J. Flaschenriem, E. M€unck, and P. L. Holland, J. Am. Chem. Soc. 126, 4522 (2004). (b) J. M. Smith, A. R. Sadique, T. R. Cundari, K. R. Rodgers, G. Lukat-Rodgers, R. J. Lachicotte, C. J. Flaschenriem, J. Vela, and P. L. Holland, J. Am. Chem. Soc. 128, 756 (2006). (c) Y. Yu, J. M. Smith, C. J. Flaschenriem, and P. L. Holland, Inorg. Chem. 45, 5742 (2006). (d) J. Vela, J. Cirera, J. M. Smith, R. J. Lachicotte, C. J. Flaschenriem, S. Alvarez, and P. L. Holland, Inorg. Chem. 46, 60 (2007).

2. b-DIKETIMINATE PRECURSORS HLMe,Me3 and TlLMe,Me3 (LMe,Me3 ¼ 2,4-BIS-(MESITYLIMIDO)PENTYL) Submitted by MATTHEW S. VARONKA and TIMOTHY H. WARREN Checked by THOMAS R. DUGAN,† RYAN E. COWLEY,† and PATRICK L. HOLLAND†

*

Department of Chemistry, Georgetown University, Washington, DC 20057-1227. Department of Chemistry, University of Rochester, Rochester, NY 14627.

†

2. b-Diketiminate Precursors HLMe,Me3 and TlLMe,Me3

5

The b-diketiminate ligand HLMe,Me3 was first reported by Budzelaar via condensation of acetylacetone with 2,4,6-trimethylaniline in 12 N HCl at 120–140 C.1 We find that the milder procedure below for HLMe,Me3 adapted from Budzelaar’s method for HLMe,Me2 offers a simple workup and is also versatile for the synthesis of other HLMe,R derivatives.2 We also include spectroscopic information for HLMe,Me2 that was prepared analogously. The synthesis of the thallium derivative TlLMe,Me3 was adapted from the published literature procedures for TlLMe,Me2 and TlLMe,Me3.3,4 General Procedures Experiments requiring air-free techniques were carried out in a dry nitrogen atmosphere using a glovebox and/or standard Schlenk techniques. Diethyl ether and tetrahydrofuran (THF) were first sparged with nitrogen and then dried by passing through activated alumina columns.5 Pentane was first washed with conc. HNO3/H2SO4 to remove olefins, stored over CaCl2, sparged with nitrogen, and 5 Deuterated solvents then dried by passing through activated alumina columns.  were sparged with nitrogen, dried over activated 4 A molecular sieves, and stored under nitrogen. 2,4,6-Trimethylaniline, 2,4-pentanedione, p-toluenesulfonic acid, and thallous acetate were purchased from Acros Organics. These reagents were used as received. Potassium hydride was obtained from Aldrich as a dispersion in mineral oil; using air-free techniques, it was filtered and washed with pentane to afford a dry powder.

A. 2,4-BIS-(MESITYLIMIDO)PENTANE (HLMe,Me3) MeCðOÞCH2 CðOÞMe þ 2 2; 4; 6-Me3 C6 H2 NH2 þ HOTs ! ½H2 LMe;Me3 ŠOTs þ 2 H2 O ½H2 LMe;Me3 ŠOTs þ Na2 CO3 ! HLMe;Me3 þ NaOTs þ NaHCO3 To a suspension of p-toluenesulfonic acid monohydrate (18.6 g, 0.098 mol) in 300 mL of toluene is added 2,4-pentanedione (9.75 g, 0.098 mol) and 2,4,6trimethylaniline (26.6 g, 0.196 mol). Using a Dean–Stark trap, the mixture is refluxed with stirring for 4 h until no further water is collected. Cooling the resulting solution gives a solid, the protonated b-diketimine as its tosylate salt, which is filtered and the solid is air-dried. This solid is taken up in 300 mL of CH2Cl2 and stirred with 200 mL of saturated Na2CO3 solution for 1 h. The organic layer is separated and dried over MgSO4. The volatiles are removed in vacuo to

6

Complexes of Bulky b-Diketiminate Ligands

yield a yellow oil.* Addition of 200 mL of ice-cold MeOH to the yellow oil followed by vigorous shaking for 1 min causes a white solid to precipitate. The slurry is stored at 35 C overnight to encourage further crystallization. The product is isolated by filtration, washed with cold methanol, and dried to yield 30.3 g (93%) of product. 1

H NMR (CDCl3): d 12.20 (s, 1, N-H), 6.89 (s, 4, Ar-H), 4.89 (s, 1, backbone-CH), 2.29 (s, 6, Ar-p-CH3), 2.16 (s, 12, Ar-o-CH3), 1.72 (s, 6, backbone-CH3); 13 C{1 H} NMR (CDCl3): d 161.62, 141.81, 134.16, 132.46, 129.09, 93.93 (backbone-CH), 21.50 (Ar-o-CH3), 20.96 (Ar-p-CH3), 18.95 (backbone-CH3). Properties The white microcrystalline solid forms colorless needles upon careful crystallization attempts. It is soluble in common organic solvents. The b-diketimine HLMe,Me2 may be prepared analogously by substituting 2,6dimethylaniline for 2,4,6-trimethylaniline in the above synthesis.3 1 H NMR (CDCl3): d 12.17 (s, 1, N-H), 7.02 (d, 4, Ar-m-H), 6.93 (t, 2, Ar-p-H), 4.86 (s, 1, backbone-CH), 2.14 (s, 6, Ar-CH3), 1.67 (s, 6, backbone-CH3); 13 C{1 H} NMR (CDCl3): d 160.72, 143.69, 132.06, 127.67, 124.19, 93.20 (backbone-CH), 20.25 (Ar-o-CH3), 18.29 (backbone-CH3). B. THALLIUM 2,4-BIS-(MESITYLIMIDO)PENTYL (TlLMe,Me3) HLMe;Me3 þ KH ! KLMe;Me3 þ H2 KLMe;Me3 þ TlOAc ! TlLMe;Me3 þ KOAc & Caution. Air-free procedures are required for use of potassium hydride, which can explosively generate hydrogen gas upon uncontrolled hydrolysis. Hydrogen gas is generated in the procedure and should not be performed in a sealed flask. Procedure A solution of HLMe,Me3 (8.00 g, 23.9 mmol) in 40 mL of THF is treated with 1.3 equiv. of dry KH (1.25 g, 31.1 mmol). The reaction is stirred overnight and then filtered through Celite to remove excess KH to yield a bright yellow filtrate. The filter cake is washed with a small amount of THF that is added to the filtrate; TlOAc (6.31 g, 23.9 mmol) is then added to this solution, which is stirred overnight in the *

The checkers obtained a solid at this step, which was treated identically and gave a 68% yield.

2. b-Diketiminate Precursors HLMe,Me3 and TlLMe,Me3

7

dark. The resulting dark green solution is filtered through Celite to yield a bright yellow filtrate. Removal of all volatiles in vacuo gives a dry yellow solid. Dissolving this solid in ca. 25 mL diethyl ether followed by chilling to 35 C results in the formation of yellow crystals, which are isolated by decanting the mother liquors to yield 8.50 g (66%) of the product after drying in vacuo. 1

H NMR (C6D6): d 6.86 (s, 4, Ar-H), 4.84 (s, 1, backbone-CH), 2.22 (s, 6, Ar-pCH3), 2.14 (s, 12, Ar-o-CH3), 1.71 (s, 6, backbone-CH3). 13 C{1 H} NMR (C6D6): d 161.87, 147.28, 132.15, 130.39, 129.31, 100.12 (backbone-CH), 24.93 (Ar-oCH3), 21.36 (Ar-p-CH3), 19.59 (backbone-CH3).

Properties The compound is both light and air sensitive and is best stored in the dark. Decomposition by light, air, or water results in black solutions or solids in which the free b-diketimine HLMe,Me3 may be detected by observation of its N-H 1 H NMR signal at d 12.20 (benzene-d6). Thallium b-diketiminates exhibit low coordination numbers in the solid state.6–8 Owing to their soft, relatively nonreducing nature and the insolubility of resulting metal halides, thallium reagents favor complete removal of the exchanged halide from the metal’s coordination sphere; thallium b-diketiminates have found use as transmetallation agents in the preparation of Co,9,10 Ni,5,11 Cu,4,12,13 and Au14 b-diketiminate complexes. Acknowledgments The authors thank Georgetown University, the Petroleum Research Fund (PRF-G and PRF-AC awards to T.H.W), and the U.S. National Science Foundation (CHE-0716304 and CHE-0135057, CAREER Award to T.H.W.) for support of this research. References 1. P. H. M. Budzelaar, A. B. van Oort, and A. G. Orpen, Eur. J. Inorg. Chem. 1485 (1998). 2. P. H. M. Budzelaar, N. N. P. Moonen, R. de Gelder, J. M. M. Smits, and A. W. Gal, Eur. J. Inorg. Chem. 753 (2000). 3. X. Dai and T. H. Warren, Chem. Commun. 1998 (2001). 4. E. Kogut, H. L. Wiencko, L. Zhang, D. E. Cordeau, and T. H. Warren, J. Am. Chem. Soc. 127, 11248 (2005). 5. A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen, and F. J. Timmers, Organometallics 15, 1518 (1996). 6. M. S. Hill, R. Pongtavornpinyo, and P. B. Hitchcock, Chem. Commun. 3720 (2006). 

The checkers obtained a yield of 48% from the first crop of crystals. Concentrating the mother liquor afforded additional crystals (total over 2 crops: 59%)

8

Complexes of Bulky b-Diketiminate Ligands

7. M. S. Hill, P. B. Hitchcock, and R. Pongtavornpinyo, Dalton Trans. 273 (2005). 8. Y. Cheng, P. B. Hitchcock, M. F. Lappert, and M. Zhou, Chem. Commun. 752 (2005). 9. P. L. Holland, T. R. Cundari, L. L. Perez, N. A. Eckert, and R. J. Lachicotte, J. Am. Chem. Soc. 124, 14416 (2002). 10. X. Dai, P. Kapoor, and T. H. Warren, J. Am. Chem. Soc. 126, 4798 (2004). 11. H. L. Wiencko, E. Kogut, and T. H. Warren, Inorg. Chim. Acta 345, 199 (2003). 12. X. Dai and T. H. Warren, J. Am. Chem. Soc. 126, 10085 (2004). 13. L. D. Amisial, X. Dai, R. A. Kinney, A. Krishnaswamy, and T. H. Warren, Inorg. Chem. 43, 6537 (2004). 14. H. V. R. Dias and J. A. Flores, Inorg. Chem. 46, 5841 (2007).

3. b-DIKETIMINATE PRECURSORS LMe,iPr2H, [LMe,iPr2Li]x, and [LtBu,iPr2K]x (LMe,iPr2¼2,4-BIS-(2,6DIISOPROPYLPHENYLIMIDO)PENTYL; LtBu,iPr2¼2,2,6,6TETRAMETHYL-3,5-BIS-(2,6-DIISOPROPYLPHENYLIMIDO) HEPTYL) Submitted by DEBASHIS ADHIKARI, BA L. TRAN, FRANCISCO J. ZUNO-CRUZ,† GLORIA SANCHEZ CABRERA,† and DANIEL J. MINDIOLA Checked by KAREN P. CHIANG,z RYAN E. COWLEY,z THOMAS R. DUGAN,z and PATRICK L. HOLLANDz

The following procedure has been slightly modified from the literature by inclusion of a few more synthetic details as well as an increment in the scale for consistency of yield.4,5 Potassium salts of LMe,iPr2 have been reported by Mair6 and Winter7 by using KN(SiMe3)2 and KH, respectively. Likewise, in Chapter 8, Roesky describes the synthesis of LMe,iPr2K from KH and LMe,iPr2H. We have, however, encountered low yields and irreproducible results in syntheses that start from potassium diketiminate salts prepared in this way, presumably because of the variable quality of commercial KH. We describe here a reproducible and facile synthesis that uses benzylpotassium3 as the potassium source, thus avoiding the use of potentially dubious KH and the hazards of explosion from the production of H2 gas.

*

Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405. † Centro de Investigaciones Quımicas, Universidad Auto´noma del Estado de Hidalgo, Pachuca, Estado de Hidalgo, 42184, Mexico. z Department of Chemistry, University of Rochester, Rochester, NY 14627.

3. b-Diketiminate Precursors LMe,iPr2H, [LMe,iPr2Li]x

9

General Procedures All manipulations (unless otherwise mentioned) were performed under a nitrogen atmosphere using standard Schlenk line or glovebox techniques. THF was dried over Na/Ph2CO and distilled into an evacuated vacuum flask equipped with a gas adapter and under a positive flow of N2 or Ar. The THF-filled flask was taken into the glovebox and stored over metallic Na (thin films). Anhydrous toluene and pentane were purchased from Aldrich in a sure-sealed reservoir (18 L) and dried by passing through two columns of activated alumina and a Cu Q-5 column under N2.1 Before use, a 5mL aliquot of each solvent was tested, qualitatively, with a drop of Na/benzophenone ketyl radical in a THF solution (1–2 drops in 3–5 mL of solvent must give a blue to purple solution). Celite was dried under reduced pressure at 180 C for 24 h. TiCl3(THF)3 was purchased from Strem and also prepared according to the literature procedure.2 All 1 H NMR spectra were referenced to solvent resonances (residual C6D5H in C6D6, 7.16 ppm). C6D6 was purchased from Cambridge Isotope Laboratories, degassed and dried over CaH2, and then vacuum  transferred to 4 A molecular sieves. Benzylpotassium was prepared by a procedure reported in the literature.3 A. 2,4-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)PENTANE (LMe,iPr2H)

MeCðOÞCH2 CðOÞMe þ 2 2; 6-ði-PrÞ2 C6 H3 NH2 þ HCl ! ½H2 LMe;Me3 ŠCl þ 2H2 O ½H2 LMe;iPr2 ŠCl þ Na2 CO3 ! HLMe;iPr2 þ NaCl þ NaHCO3 Procedure Manipulations are performed in the air. In a two-neck 500-mL round-bottomed flask, 1,4-pentanedione (6.68 g, 0.067 mol) is mixed with 300 mL of ethanol and 2,6-diisopropylaniline (28.67 g, 0.162 mol). To the mixture is added 7.5 mL of conc. hydrochloric acid (12 M) and the solution is refluxed with vigorous stirring at 100 C for 3 days. After 6 h, a white precipitate begins to form, but the reaction must be continued for the full 3 days for complete conversion. The slurry is allowed to cool to room temperature and then filtered. The filtered solid is dried under reduced pressure, and the filtrate is evaporated on a rotary evaporator. The dried mass is combined with the filtrate residue and the mixture is refluxed in 250 mL hexane at 80 C for 1 h. After cooling the mixture, the slurry is filtered, and the solid residue is treated with 300 mL of a saturated aqueous solution of Na2CO3 and 500 mL of CH2Cl2. The slurry is stirred until the solid dissolves, giving a yellowish organic solution and a pale yellow aqueous layer. The organic layer is separated

10

Complexes of Bulky b-Diketiminate Ligands

using a separatory funnel and the solution is dried over MgSO4. The solution is filtered again and dried under reduced pressure to yield a slightly yellow residue that upon washing with 50 mL of cold methanol ( 20 C) yields white LMe,iPr2H as a fluffy powder (21.42 g, 0.051 mol, 77% yield).* The compound is characterized by 1 H NMR spectroscopy that was compared with that reported in the literature.5 1

H NMR (C6D6): d 12.44 (s, 1H, N-H), 7.14–7.09 (m, 6H, Ar-H), 4.85 (s, 1H, CH), 3.27 (m, 4H, CH(CH3)2), 1.63 (s, 6H, NC(CH3)), 1.18 (d, JH H ¼ 7 Hz, 12H, CH (CH3)2), 1.12 (d, JH H ¼ 7 Hz, 12H, CH(CH3)2). Properties

LMe,iPr2H is a white crystalline solid that is soluble in organic solvents including n-pentane and n-hexane. LMe,iPr2H is not soluble in water and is poorly soluble in other polar solvents such as MeOH and EtOH. Solids are indefinitely stable in air and readily form the iminium salt [LMe,iPr2H2]Cl upon exposure to 12 M HCl. As a solid, LMe,iPr2H gradually turns pale yellow in air, but the material can be purified by recrystallization by concentrating an Et2O solution followed by cooling to 20 C for >12 h. It is recommended, however, to store the pure white free base under an inert atmosphere (or under vacuum) to avoid gradual tainting. B. LITHIUM 2,4-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)PENTYL ([LMe,iPr2Li]x) HLMe;iPr2 þ BuLi ! ½LMe;iPr2 LiŠx þ BuH & Caution. Butyllithium is pyrophoric in air and should be handled exclusively under dry nitrogen or argon. This reaction is extremely exothermic, so the addition of n-BuLi should be performed at low temperatures and not be rushed. Procedure In a 250-mL round-bottomed flask, LMe,iPr2H (5.00 g, 0.012 mol) is dissolved in 100 mL of hexane and the solution cooled to 35 C. To the cooled solution a 1.6 M n-BuLi solution in hexane (7.84 mL, 0.013 mol) is added dropwise, and the solution is stirred for 12 h at room temperature. During the course of this time, a white precipitate gradually appears. The suspension is cooled to 35 C over 12 h, and the solid is collected by filtration, washed with 10 mL of cold hexane, and then dried under reduced pressure. The filtrate collected from the first batch is concentrated to 30 mL under reduced *

The checkers omitted the step where the residue was refluxed in hexane, obtaining a final yield of 72%.

3. b-Diketiminate Precursors LMe,iPr2H, [LMe,iPr2Li]x

11

pressure and the solution is cooled again to 35 C. After 12 h, a second batch of solid is collected via filtration, washed with cold hexane, and dried under reduced pressure. The combined yield for the two batches is 2.85 g (0.007 mol, 56% yield). Compound [LMe,iPr2Li]x is characterized by 1 H NMR spectroscopy by comparison to that reported in the literature.4 The structural chemistry of lithium diketiminate complexes has been investigated.4 1

H NMR (C6D6): d 7.21–7.18 (m, 6H, Ar-H), 4.90 (s, 1H, g-CH), 3.15 (m, 4H, CH (CH3)2), 1.83 (s, 6H, NC(CH3)), 1.21 (d, JH H ¼ 7 Hz, 12H, CH(CH3)2), 1.18 (d, JH H ¼ 7 Hz, 12H, CH(CH3)2). Properties Compound [LMe,iPr2Li]x is a white amorphous solid, which is soluble in donor solvents such as Et2O and THF. The salt has very low solubility in hydrocarbons such as n-pentane and n-hexane but can be dissolved in copious amounts of benzene and toluene. The compound [LMe,iPr2Li]x decomposes rapidly in halogenated solvents and upon exposure to air. It is recommended that solids not be stored for extended periods of time, even if inside a glovebox. For the preparation of its transition metal derivatives, it is preferable to use fresh [LMe,iPr2Li]x or generate it in situ before use. In the presence of donor solvents such as Et2O and THF, [LMe, iPr2 Li]x forms yellow adducts.4 The binding is exothermic, and it is therefore recommended to add the salt to the solution and not the reverse. C. POTASSIUM 2,2,6,6-TETRAMETHYL-3,5-BIS-(2,6DIISOPROPYLPHENYLIMIDO)HEPTYL ([LtBu,iPr2K]x) LtBu;iPr2 H þ KCH2 Ph ! ½LtBu;iPr2 KŠx þ PhMe Procedure & Caution. KCH2Ph is a highly pyrophoric that should be handled only in an inert atmosphere. Upon contact with O2 or H2O, solid benzylpotassium will immediately deflagrate. This reaction to produce [LtBu,iPr2K]x is extremely exothermic, so it is recommended that the addition of KCH2Ph be performed slowly and at low temperatures. A solution of LtBu,iPr2H (2.15 g, 4.27 mmol) in 40 mL of diethyl ether is placed in a 250-mL round-bottomed flask and frozen in a cold well for 0.5 h. To the thawing solution is added benzylpotassium3 (557 mg, 4.27 mmol) in portions. The 

The checkers performed the reaction on a larger scale (27 mmol) and obtained a yield of 75%.

12

Complexes of Bulky b-Diketiminate Ligands

suspension is slowly warmed to room temperature, and the orange solids gradually dissolve to give a yellow solution. After stirring the solution at room temperature for 1.5 h, removal of the ethereal solution affords a canary yellow solid, which is triturated with 25 mL of cold pentane and vacuum filtered through a porous frit to afford a pale yellow product. The product is further washed with 15 mL of cold pentane, dried, and stored at 37 C. Yield: 91% (2.10 g, 3.88 mmol). 1 H NMR spectra of [LtBu,iPr2K]x indicate the absence of solvent. The degree of aggregation of this material was not investigated. 1

H NMR (C6D6): d 7.00 (d, 4H, J ¼ 7 Hz, m-Ar-H), 6.81 (t, 2H, J ¼ 7 Hz, p-Ar-H), 4.93 (s, 1H, a-H), 3.26 (m, 4H, CH(CH3)2, 1.37 (s, 18H, C(CH3)3), 1.32 (d, 12H, J ¼ 7 Hz, CH(CH3)2, 0.94 (d, 12H, J ¼ 7 Hz, CH(CH3)2). 13 C NMR (C6D6): d 166.0 (ArN(C(CH3)3)CCHC(C(CH3)3)NAr), 151.4 (Ar), 144.8 (Ar), 135.7 (Ar), 133.2 (Ar), 123.4 (Ar), 118.1 (Ar), 89.6 (ArN(C(CH3)3)CCHC(C(CH3)3)NAr), 44.0 (ArN(C(CH3)3)CCHC(C(CH3)3)NAr), 32.5 (ArN(C(CH3)3)CCHC(C (CH3)3)NAr), 31.6 (Ar-2,6-(CH(CH3)2), 27.0 (Ar-2,6-(CH(CH3)2), 24.8 (Ar2,6-(CH(CH3)2), 23.4 (Ar-2,6-(CH(CH3)2), 22.69 (Ar-2,6-(CH(CH3)2). Properties Compound [LtBu,iPr2K]x is a pale yellow amorphous solid that is soluble in THF. The salt is insoluble in hydrocarbons such as n-pentane and n-hexane, and partially soluble in benzene, toluene, and Et2O. Compound [LtBu,iPr2K]x decomposes rapidly in halogenated solvents such as CH2Cl2 and CCl4 and also upon exposure to air. It is also recommended that solids not be stored for extended periods of time, even if inside a glovebox. It is preferable to isolate fresh [LtBu,iPr2K]x for subsequent use. Acknowledgments The authors thank Indiana University-Bloomington, the Camille and Henry Dreyfus Foundation (New Faculty and Teacher-Scholar Awards to D.J.M.), the Alfred P. Sloan Foundation (fellowship to D.J.M.), and the U.S. National Science Foundation (CHE-0348941, PECASE Award to D.J.M.) for support of this research.



The checkers obtained a yield of 93% using the method described. The checkers also performed the reaction on a similar scale at room temperature and obtained a solid having identical properties, with a yield of 95%. It is difficult to remove the final traces of toluene from the solid under vacuum, as is evident from 1H NMR spectra.

4. b-Diketiminate Precursors LtBu,iPr2H AND LtBu,iPr2

13

References 1. A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen, and F. J. Timmers, Organometallics 15, 1518 (1996). 2. N. A. Jones, S. T. Liddle, C. Wilson, and P. L. Arnold, Organometallics 26, 755 (2007). 3. P. J. Bailey, R. A. Coxall, C. M. Dick, S. Fabre, L. C. Henderson, C. Herber, S. T. Liddle, D. LoronoGonzalez, A. Parkin, and S. Parsons, Chem. Eur. J. 9, 4820 (2003). 4. M. Stender, R. J. Wright, B. E. Eichler, J. Prust, M. M. Olmstead, H. B. Roesky, and P. P. Power, Dalton Trans. 3465 (2001). 5. J. Feldman, S. J. McLain, A. Parthasarathy, W. J. Marshall, J. C. Calabrese, and S. D. Arthur, Organometallics 16, 1514 (1997). 6. W. Clegg, E. K. Cope, A. J. Edwards, and F. S. Mair, Inorg. Chem. 37, 2317 (1998). 7. H. M. El-Kaderi, M. J. Heeg, and C. H. Winter, Polyhedron 25, 224 (2006).

4. b-DIKETIMINATE PRECURSORS LtBu,iPr2H AND LtBu,iPr2Li(THF) (LtBu,iPr2¼2,2,6,6-TETRAMETHYL-3,5BIS-(2,6-DIISOPROPYLPHENYLIMIDO)HEPTYL) Submitted by RYAN E. COWLEY, KAREN P. CHIANG, and PATRICK L. HOLLAND Checked by DEBASHIS ADHIKARI,† FRANCISCO J. ZUNO-CRUZ,z GLORIA SANCHEZ CABRERA,z and DANIEL J. MINDIOLA†

The b-diketiminate ligand with tert-butyl substituents on the backbone (LtBu,iPr2) gives especially extreme hindrance in late transition metal complexes. Studies on the vanadium chemistry of bulky b-diketiminates showed that this ligand did not coordinate to vanadium or titanium.1 Only under the right conditions can this ligand be coordinated to Ti(III), albeit in low yields.2 In iron(II) and nickel(II) complexes, the LtBu,iPr2 ligand gives three-coordinate monomers LtBu,iPr2MCl, even though LMe,iPr gives [LMe,iPr2M(m-Cl)]2 under identical conditions.3 At first glance, this distinct increase in size may be surprising because the location of the large t-butyl groups is far from the metal binding site, and directed away from the metal. However, steric interactions between the tertbutyl groups and the neighboring 2,6-diisopropylphenyl groups push the latter toward the ‘‘open’’ side of the ligand and increase the extent to which the metal is blocked from additional ligands. This size difference has been shown by side-to-

*

Department of Chemistry, University of Rochester, Rochester, NY 14627. Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405. z Centro de Investigaciones Quımicas, Universidad Auto´noma del Estado de Hidalgo, Pachuca, Estado de Hidalgo, 42184, Mexico. †

14

Complexes of Bulky b-Diketiminate Ligands

side comparison of three-coordinate iron alkyl complexes of the two diketiminate ligands.4 Because of the hindrance near the imine carbon atoms, the diimine LtBu,iPr2H cannot be synthesized through a double condensation, as in the other ligands. Budzelaar sidestepped this problem using a convergent synthesis that couples the two sides of the ligand.1 Both sides derive from a common intermediate, an imine chloride which is prepared from pivaloyl chloride. Half of this imine chloride is methylated to give a methyl tert-butyl imine, which is then deprotonated and treated with the remaining half of the imine chloride to give the final ligand. The synthesis below, which is very little changed from that reported by Budzelaar, gives the ligand in a total yield of 58% in four steps.1 The 1 H NMR spectrum of the final ligand has broad signals at room temperature, presumably from exchange between diimine and imine–enamine tautomers, which has a rate similar to the NMR timescale. A method for preparing the lithium salt of this ligand is given here; please refer to the previous chapter to find a method for preparing the potassium salt of this ligand. General Procedures All materials were purchased from Aldrich and used as received, unless otherwise specified. NMR spectra are referenced to residual C6D5H at 7.16 ppm or CHCl3 at 7.26 ppm. Solvents for the final two steps were dried by passing HPLC-grade solvents through columns of activated alumina and Cu Q-5 (Glass Contour Co.).

A. N-PIVALOYL-2,6-DIISOPROPYLANILIDE (DIPPNHC(O)tBu) Me3 CðOÞCl þ 2; 6-ði-PrÞ2 C6 H3 NH2 þ Et3 N ! 2; 6-ði-PrÞ2 C6 H3 NHCðOÞCMe3 þ Et3 NHCl Procedure 2,6-Diisopropylaniline (97.5 g, 0.55 mol), triethylamine (70 mL, 0.50 mol), dichloromethane (200 mL), and a large stir bar are added to a 1000-mL roundbottomed flask to give a colorless solution. A solution of pivaloyl chloride (62 mL, 0.50 mol) in dichloromethane (200 mL) is added to a pressure-equalizing addition funnel, and this solution is added dropwise to the vigorously stirring aniline solution over 2 h. Although pivaloyl chloride is sensitive to water, predrying the triethylamine and dichloromethane is not required. The reaction is exothermic, so

4. b-Diketiminate Precursors LtBu,iPr2H AND LtBu,iPr2

15

slow addition is necessary. The solution has a pale pink or green color, and a white precipitate is evident. After stirring the mixture for an additional 30 min, the slurry is chilled to 0 C, and the fluffy solid is collected by filtration.* The solid is washed with diethyl ether (3  150 mL) to remove excess aniline and with copious amounts of water (4  200 mL) to remove triethylammonium chloride. Finally, the solid is dried under vacuum for at least 12 h to afford DIPPNH(C¼O)(tBu) (121 g, 93% yield). Typical isolated yields are greater than 90%, and the product is stable to air and water. Purity is determined by 1 H NMR spectroscopy. 1

H NMR (CDCl3): d 7.29 (m, 2H, p-Ar), 7.15 (d, 2H, m-Ar, J ¼ 7.6 Hz), 6.80 (br, 1H, N-H), 3.00 (sept, 2H, CH(CH3)3, J ¼ 6.8 Hz), 1.36 (s, 9H, C(CH3)3), 1.18 (d, 12H, CH(CH3)2, J ¼ 6.8 Hz). B. DIPPN¼C(Cl)tBu 2; 6-ði-PrÞ2 C6 H3 NHCðOÞCMe3 þ PCl5 ! 2; 6-ði-PrÞ2 C6 H3 N¼CðClÞCMe3 þ HCl þ POCl3 Procedure A 2000-mL three-necked flask containing a slurry of DIPPNH(C¼O)(tBu) (121 g, 0.46 mol) in 1000 mL of benzene (predrying benzene is not necessary) is fitted with a glass stopper and two hose adapters. One hose attaches to a N2 inlet, and the other is allowed to bubble through saturated sodium carbonate to neutralize gaseous HCl produced in the reaction. The headspace of the flask is purged with N2 for 10 min, and the flow rate is reduced to a slow bubble. Solid PCl5 (106 g, 0.51 mol) is added in small portions (5–10 g) over a 90-min period by opening the stoppered joint against a positive N2 flow, adding the solid, and replacing the stopper. Slow addition of PCl5 is necessary because the reaction is exothermic. During the course of the reaction all solids dissolve, and the solution develops a yellowish color. The mixture is stirred for an additional 1 h after the addition of PCl5 is complete. The two hose adapters are removed from the flask and replaced with ground glass stoppers. The third neck is fitted with a distillation head and benzene and POCl3 are removed by distillation directly from the reaction flask at ambient pressure under a N2 atmosphere. (Caution: POCl3 produces gaseous HCl upon contact with moisture or moist air.) The residue is then transferred into a smaller single-necked flask and chloroimine is distilled under vacuum (82 C, *

Using 2,6-diisopropylaniline from Acros Organics, the checkers conducted the reaction at a lower concentration and obtained a tacky product.

16

Complexes of Bulky b-Diketiminate Ligands

0.10 mbar) through a Vigreux column. The product (100 g, 83%) is a colorless oil and is best stored under an atmosphere of N2 to prevent reaction with moisture, which converts it to DIPPNH(C¼O)(tBu). Purity is established by 1 H NMR spectroscopy. Occasionally, the distillate contains traces of DIPPNH(C¼O)(tBu) (up to 10% based on 1 H NMR integration), in which case a second distillation through a Vigreux column is necessary. 1

H NMR (CDCl3): d 7.14 (m, 3H, m- and p-Ar), 2.74 (sept, 2H, CH(CH3)2, J ¼ 6.8 Hz), 1.43 (s, 9H, C(CH3)3), 1.18 (d, 12H, CH(CH3)3, J ¼ 6.8 Hz). C. DIPPN¼C(Me)tBu

2; 6-ði-PrÞ2 C6 H3 N¼CðClÞCMe3 þ MeLi ! 2; 6-ði-PrÞ2 C6 H3 N¼CðMeÞCMe3 þ LiCl Procedure & Caution. Methyllithium is pyrophoric in air and should be handled exclusively under dry nitrogen or argon. This reaction is extremely exothermic, so the addition should be performed carefully at low temperatures. An oven-dried (150  C) 500-mL Schlenk flask is charged with DIPPN¼C(Cl) ( Bu) (45.3 g, 0.16 mol), rigorously dry diethyl ether (200 mL), and a stir bar under a N2 atmosphere to give a colorless solution, and the flask is sealed with a septum and removed from the glovebox. (It is easier to perform the reaction in a cold well in a drybox, if the equipment is available.) The solution is chilled to 78 C in a dry ice/acetone cold bath, and methyllithium (121 mL, 1.6 M solution in diethyl ether, 0.19 mol) is added to the stirring reaction mixture in 5-mL portions over 30 min. The mixture is allowed to slowly warm and stirred at ambient temperature, upon which a white precipitate is observed. (Caution: A slow flow of N2 through the septum and out to an oil bubbler is necessary to ensure that the reaction vessel does not develop pressure since the reaction is exothermic and the ether solvent is quite volatile.) After 12 h,† the mixture is exposed to air by removing the septum and ice (about 5 g) is carefully added in small portions until effervescence ceases. Water (100 mL) is added, and the mixture is transferred to a separatory funnel where the aqueous layer is removed. The organic layer is extracted twice more with t

 †

The checkers distilled at 125–127 C at 7 mbar. The checkers report that a 3-h reaction time is sufficient for full conversion.

4. b-Diketiminate Precursors LtBu,iPr2H AND LtBu,iPr2

17

water (2  100 mL), dried with anhydrous MgSO4, and filtered through coarse filter paper. The volatile materials are removed under vacuum to afford a light yellow oil. Pure DIPPN¼C(Me)(tBu) is distilled through a Vigreux column under vacuum (72 C, 0.02 mbar) as a colorless oil (36.0 g, 86%). The oil is stable for months to air and moisture. Purity is established by 1 H NMR spectroscopy. 1

H NMR (CDCl3): d 6.97–7.09 (m, 3H, Ar-H), 2.68 (sept, 2H, CH(CH3)2, J ¼ 6.9 Hz), 1.66 (s, 3H, CH3), 1.28 (s, 9H, C(CH3)3), 1.13 (d, 6H, CH(CH3)3, J ¼ 6.9 Hz), 1.11 (d, 6H, CH(CH3)3, J ¼ 6.9 Hz). D. 2,2,6,6-TETRAMETHYL-3,5-BIS-(2,6DIISOPROPYLPHENYLIMIDO)HEPTANE ([DIPPN¼C(tBu)]2CH2, LtBu,iPrH) 2; 6-ði-PrÞ2 C6 H3 N¼CðMeÞCMe3 þ BuLi ! 2; 6-ði-PrÞ2 C6 H3 N¼CðCH2 LiÞCMe3 þ BuH 2; 6-ði-PrÞ2 C6 H3 N¼CðClÞCMe3 þ 2; 6-ði-PrÞ2 C6 H3 N¼CðCH2 LiÞCMe3 ! LtBu;iPr H þ LiCl Procedure

In a N2 glovebox, an oven-dried (150 C) 500-mL Schlenk flask is charged with DIPPN¼C(Me)(tBu) (48.6 g, 0.18 mol), rigorously dry diethyl ether (250 mL, pentane can also be used), dried N,N,N0 ,N0 -tetramethylethylenediamine (40 mL, 0.26 mol), and a stir bar to give a colorless solution. The solution is chilled to 78 C and n-butyllithium (76 mL, 2.5 M in hexanes, 0.19 mol) is added slowly in 5-mL portions over 15 min. (Note: Although using a glovebox cold well is convenient, sealing the flask with a septum, removing the flask from the glovebox, and chilling in a dry ice/acetone bath under dynamic N2 is also appropriate.) The flask is sealed with a ground glass stopper and the stopcock is left open to allow butane to escape. The mixture is allowed to slowly warm to ambient temperature for 16 h. The mixture is then cooled to 78 C and a solution of DIPPN¼C(Cl) (tBu) (50.4 g, 0.18 mol) in diethyl ether (50 mL) is added. The resulting slurry is allowed to slowly warm and stirred at ambient temperature for 18 h, whereupon the



The checkers conducted the reaction at 0 C and did not distill the product. The crude product was assayed by 1H NMR spectrum and was used in subsequent steps without further purification.

18

Complexes of Bulky b-Diketiminate Ligands

solution develops a yellowish color and a white precipitate forms. The mixture is removed from the glovebox and heated at reflux in an oil bath for 2 h under N2. The slurry is cooled and exposed to air where it is carefully quenched with ice and water (200 mL). The mixture is transferred to a separatory funnel, and the aqueous layer is discarded. The organic layer is extracted twice more with water (2  200 mL), dried with anhydrous MgSO4, and filtered through coarse filter paper. The volatile materials are removed under vacuum to afford a sticky yellow solid. This solid is dissolved in 400 mL of boiling hexanes, and the extract is slowly cooled to 25 C to give colorless block-shaped crystals of LtBu,iPrH in two crops (79.1 g, 87%). When stored in air, LtBu,iPrH slowly turns yellow over a period of weeks; therefore, keeping LtBu,iPrH under an atmosphere of N2 is appropriate for longterm storage. Purity is established by 1 H NMR spectroscopy. 1

H NMR (CDCl3): d 7.07–6.97 (m), 3.21 (br), 2.68 (br), 1.21 (s), 1.09 (s), 1.05 (br) ppm. The 1 H NMR spectrum of LtBu,iPrH shows overlapped and broadened peaks due to the mixture of bis(imine) and imine–enamine tautomers. At 70 C in CDCl3, the spectrum is better resolved. The major component (ca. 95%) is the bis(imine) tautomer: d 7.04–6.92 (m, 6H, m- and p-Ar), 3.26 (s, 2H, a-CH2), 2.61 (broad m, 4H, CH(CH3)2), 1.19 (d, 12H, CH(CH3)3, J ¼ 8 Hz), 1.07 (s, 18H, C(CH3)3), 1.03 (d, 12H, CH(CH3)3, J ¼ 8 Hz) ppm. The minor (ca. 5%) component is assigned to the imine–enamine tautomer: d 11.0 (s, 1H, N-H), 5.43 (s, 1H, a-CH), 3.15 (sept, 1H, CH(CH3)2). The remaining alkyl and aryl resonances from the imine–enamine tautomer overlap with the major component. E. LITHIUM 2,2,6,6-TETRAMETHYL-3,5-BIS-(2,6DIISOPROPYLPHENYLIMIDO)HEPTYL (LtBu,iPr2Li, THF ADDUCT) LtBu;iPr2 H þ BuLi ! LtBu;iPr2 LiðTHFÞ þ BuH Procedure & Caution. Butyllithium is pyrophoric in air and should be handled exclusively under dry nitrogen or argon. This reaction is extremely exothermic, so n-BuLi should be added slowly. It is important to vent the reaction. This manipulation is also possible outside of the glovebox by adding n-butyllithium through a septum and allowing butane to escape through an oil bubbler.

In a N2 glovebox, an oven-dried (150 C) 500-mL Schlenk flask is charged with LtBu,iPrH (24.5 g, 54.6 mmol), anhydrous THF (150 mL), and a stir bar to

4. b-Diketiminate Precursors LtBu,iPr2H AND LtBu,iPr2

19

give a colorless solution. The flask is kept open while a solution of n-butyllithium (22.5 mL, 2.5 M solution in hexanes, 56.3 mmol) is slowly added to the stirring solution, causing effervescence and a color change to dark yellow-orange. Following addition of butyllithium, the mouth of the flask is sealed with a ground glass stopper and the stopcock is left open to allow additional butane to vent. After stirring the solution for 30 min, the flask is closed, removed from the glovebox, and the solution is heated in a 60 C oil bath for 3 h. The volatile materials are removed in vacuum, leaving a yellow residue. The flask is returned to the glovebox. The solid is freed from any excess butyllithium by briefly shaking with pentane (100 mL) and decanting the supernatant. This wash is repeated with an additional portion of pentane (100 mL), and the yellow solid is dried under vacuum to give LtBu,iPr2Li(THF) (26.6 g). Additional product is obtained by reducing the volume of the combined pentane washes to 30 mL and cooling to 45 C. This solid is collected on an oven-dried fritted glass funnel and washed with cold pentane (10 mL, 45 C) to obtain additional LtBu,iPr2Li(THF) (2.60 g, combined yield 92%). Purity is established by 1 H NMR spectroscopy. 1

H NMR (C6D6): d 6.94–7.03 (m, 6H, Ar-H), 5.25 (s, 1H, a-H), 3.49 (sept, 4H, CH (CH3)2, J ¼ 7.0 Hz), 2.31 (br, 4H, OCH2CH2), 1.38 (s, 18H, C(CH3)3), 1.37 (d, 12H, CH(CH3)2, J ¼ 7.0 Hz), 1.11 (s, 12H, CH(CH3)2, J ¼ 7.0 Hz), 0.92 (br, 4H, OCH2CH2). Properties Solid LtBu,iPr2Li(THF) is air and moisture sensitive but stable indefinitely when stored under N2. It is suitable for most further syntheses, but recrystallization is recommended to ensure complete removal of traces of butyllithium before use with metal salts that are prone to reduction, for example, copper(I) derivatives.5 References 1. P. H. M. Budzelaar, A. B. van Oort, and A. G. Orpen, Eur. J. Inorg. Chem. 1485 (1998). 2. (a) F. Basuli, B. C. Bailey, L. A. Watson, J. Tomaszewski, J. C. Huffman, and D. J. Mindiola, Organometallics 24, 1886 (2005). (b) F. Basuli, R. L. Clark, B. C. Bailey, D. Brown, J. C. Huffman, and D. J. Mindiola, Chem. Commun. 2250 (2005). 3. (a) J. M. Smith, R. J. Lachicotte, and P. L. Holland, Chem. Commun. 1542 (2001). (b) N. A. Eckert, E. M. Bones, R. J. Lachicotte, and P. L. Holland, Inorg. Chem. 42, 1720 (2003). (c) N. A. Eckert, J. M. Smith, R. J. Lachicotte, and P. L. Holland, Inorg. Chem. 43, 3306 (2004). 4. J. Vela, S. Vaddadi, T. R. Cundari, J. M. Smith, E. A. Gregory, R. J. Lachicotte, C. J. Flaschenriem, and P. L. Holland, Organometallics 24, 5494 (2005). 5. D. J. E. Spencer, N. W. Aboelella, A. M. Reynolds, P. L. Holland, and W. B. Tolman, J. Am. Chem. Soc. 124, 2108 (2002).

20

Complexes of Bulky b-Diketiminate Ligands

5. SCANDIUM TRICHLORIDE TRIS(TETRAHYDROFURAN) AND b-DIKETIMINATE-SUPPORTED SCANDIUM CHLORIDE COMPLEXES Submitted by PAUL G. HAYES and WARREN E. PIERS† Checked by DEBASHIS ADHIKARIz and DANIEL J. MINDIOLAz

General Procedures All manipulations were performed either in an inert atmosphere glovebox or on a double manifold high-vacuum line equipped with Teflon needle valves.1 Toluene and hexanes were dried and purified using the Grubbs/Dow purification system2 and stored in evacuated bombs. Diethyl ether and benzene-d6 were dried and stored over sodium/benzophenone ketyl. Compounds [LMe,iPr2Li]x3–5 (LMe,iPr2 ¼ [ArNC (Me)]2CH , Ar ¼ 2,6-iPr2C6H3) and [LtBu,iPr2Li]x5 (LtBu,iPr2 ¼ [ArNC(tBu)]2CH , Ar ¼ 2,6-iPr2C6H3) were prepared according to literature procedures. 1 H and 13 C NMR spectra were referenced to SiMe4 through the residual solvent signals. A. SCANDIUM TRICHLORIDE TRIS(TETRAHYDROFURAN), ScCl3(THF)3*

Sc2 O3 þ 6 HCl þ 9 H2 O ! 2 ScCl3 ðH2 OÞ6 ScCl3 ðH2 OÞ6 þ 6 SOCl2 þ 3 THF ! ScCl3 ðTHFÞ3 þ 6 SO2 þ 12 HCl Procedures & Caution. This reaction is extremely exothermic, so the SOCl2/THF solution should be added carefully. ScCl3(THF)3 is prepared by a modified literature procedure.6 A 1-L roundbottomed flask equipped with a condenser is charged with Sc2O3 (20.3 g, §

The checkers converted commercially available ScCl3(H2O)6 (Strem Chemicals) to ScCl3(THF)3 using the protocol in Ref. 6. It should be noted that the checkers did not use a swivel frit, but rather, conducted manipulations inside a glovebox using a commercially available microporous frit (medium porosity). *

Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada, T1K 3M4. † Department of Chemistry, University of Calgary, Calgary, Alberta, Canada, T2N 1N4. z Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405.

5. Scandium Trichloride Tris(Tetrahydrofuran) and b-Diketiminate

21

0.147 mol) and 6 M HCl (300 mL). The reaction mixture is heated at reflux for 3 h during which period the mixture changes from a cloudy white suspension to a clear yellow solution. The solvent is removed by rotary evaporation to give ScCl3(H2O)6 as a thick yellow oil. A solution of SOCl2 (350 mL) in THF (250 mL) is added dropwise to the oil over 2 h, during which time a large quantity of gas (HCl and SO2) evolves. Precipitation of a white solid, followed by a gradual change to a clear yellow solution, also occurs during this period. The reaction mixture is then heated at 86 C for 18 h, and the solvent is removed by rotary evaporation to afford an oily yellow solid. The moisture-sensitive mixture is quickly attached to a swivel-frit1 apparatus and evacuated. Et2O (200 mL) is added to the residue, which is then stirred for 20 min and filtered. The fine white powder is washed with Et2O (4  50 mL) and the solvent is removed in vacuo. Yield: 100.8 g, 0.274 mol, 93%. IR (neat):6 1004 (s), 846 (s) cm 1. Properties The product is a fine white powder that must be stored under an inert atmosphere as it rapidly absorbs moisture from air. B. SCANDIUM 2,4-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)PENTYL DICHLORIDE TETRAHYDROFURAN, (LMe,iPr2)ScCl2(THF) ScCl3 ðTHFÞ3 þ LMe;iPr2 Li ! ðLMe;iPr2 LiÞScCl2 ðTHFÞ þ 2 THF þ LiCl A 250-mL round-bottomed flask is attached to a swivel-frit1 assembly and charged  with [LMe,iPr2Li]x (5.00 g, 11.8 mmol) and ScCl3(THF)3 (5.00 g, 13.6 mmol).  Toluene (90 mL) is vacuum distilled into the evacuated flask at 78 C, and the mixture is heated with stirring at reflux for 16 h. During this period, the solution gradually changes from almost colorless to pale yellow. The reaction mixture is hot filtered to remove LiCl and excess ScCl3(THF)3, and the toluene is removed from the filtrate in vacuo. The residue is sonicated for 10 min in hexanes (60 mL), followed by cold ( 78 C) filtration. After exposure to vacuum for 6 h, (LMe,iPr2) ScCl2(THF) is isolated in 94% yield (6.72 g, 11.1 mmol). Anal. Calcd. for C33H49N2Cl2OSc: C, 65.44; H, 8.15; N, 4.63. Found: C, 65.35; H, 8.61; N, 4.61. 1 H NMR (benzene-d6): d 7.21 (m, 6H, C6H3), 5.32 (s, 1H, CH), 3.56 (sp, 4H, CHMe2, JHH ¼ 6.8 Hz), 3.48 (m, 4H, OCH2CH2), 1.65 (s, 6H, NCMe), 1.48 

The checkers performed the same reaction inside an N2 filled glovebox equipped with a cold well. Similar yields were obtained as long as the glassware is oven dried and the N2 atmosphere contains 200 C. Properties Complex (LMe,iPr2)TiCl2(THF) (deep green) is a close analogue of Budzelaar’s nonsolvento complex (LMe,iPr2)TiCl2 (deep red-brown).6 Budzelaar reported that THF can be removed by repeated distillation of toluene solutions at 1 bar.6 Although (LMe,iPr2)TiCl2(THF) can be stored indefinitely under an inert atmosphere, it is recommended that samples be stored at 35 C in a well-sealed vial since traces of O2, moisture, or other oxidants (e.g., CCl4) readily promote decomposition. Both the solvent-free and THF complexes have similar solubilities, being soluble in toluene, benzene, and THF, and insoluble in pentane and hexane. The complex is partially soluble in Et2O. The complex gradually decomposes in CH2Cl2. Decomposition to unidentified products also occurs when either complex is exposed to air, moisture, or halogenated solvents such as CCl4. Related Complexes Complex (LMe,iPr2)TiCl2(THF) can be alkylated to give the dimethyl derivative, (LMe,iPr2)TiMe2. When combined with B(C6F5)3, the complex forms a highly active catalyst for the polymerization of propene and 1-hexene.6 Atactic polymers can be generated from the polymerization reactions.6 THF coordi-

6. b-Diketiminate-Supported Titanium and Vanadium Dichloride

27

nation to (LMe,iPr2)TiCl2 does not seem to impede transmetallation reactions. Likewise, THF can be readily displaced when the alkyl substituent is sterically encumbering. For example, treatment of (LMe,iPr2)TiCl2(THF) with 2 equiv of LiCH2tBu, LiCH2SiMe3, and LiNHAr (Ar ¼ 2,6-iPr2C6H3) affords the fourcoordinate Ti(III) products, (LMe,iPr2)Ti(CH2tBu)2,7 (LMe,iPr2)Ti(CH2SiMe3)2,8 and (LMe,iPr2)Ti(NHAr)2,9 respectively. Treatment of (LMe,iPr2)TiCl2(THF) with 1 equiv of NaN(SiMe3)2 provides (LMe,iPr2)TiCl[N(SiMe3)2] and free THF.10 B. SYNTHESIS OF (LtBu,iPr2)TiCl2 LiLtBu;iPr2 þ TiCl3 ðTHFÞ3 ! ðLtBu;iPr2 ÞTiCl2 þ 3 THF þ LiCl Procedure In a 350- or 500-mL thick-walled glass round-bottomed pressure vessel (CHEMGLASS) in the glovebox, TiCl3(THF)3 (1.3 g, 0.004 mol) is transferred into 30 mL of toluene, and the suspension cooled to 35 C. In a conical flask, [LtBu,iPr2Li]x (1.785 g, 0.004 mol) is taken up with 30 mL of toluene. The toluene solution of [LtBu,iPr2Li]x is transferred by a pipette to the suspension of TiCl3(THF)3 in toluene. During the addition of the salt, the blue color of the TiCl3(THF)3 suspension gradually changes to greenish brown. Upon completing the addition, the thick-walled reaction vessel (Fig. 1) is closed with a Teflon-coated cap. The reaction vessel is brought outside the glovebox and heated at 110 C for 3 days with vigorous stirring. Within 2 h of initial heating, the color of the solution changes to intense green. After completion of the reaction, the reaction vessel is brought back into the glovebox, the solution is filtered through a Celite bed, and the volume of the filtrate is reduced to 20 mL until green microcrystals begin to form. After allowing the solution to warm up to the box temperature to redissolve the crystals, 25 mL of hexane is added and the solution is cooled to 35 C for 24 h. At this time, intense green microcrystals of (LtBu,iPr2)TiCl2 are separated after filtering the solution through a medium porosity frit, and the solids are washed with 10 mL of hexane to afford 1.27 g of product (0.002 mol, 58% yield).* The filtrate from the first crystallization appears reddish in color. Reducing the volume of the latter solution to 5 mL and subsequent cooling to 35 C over 12–16 h yields red crystals of (LtBu,iPr2)Ti¼NAr(Cl) (335 mg, 0.0004 mol, 12.5% yield).11 Anal. Calcd. for C35H53N2Cl2Ti: C, 67.73; H, 8.61; N, 4.51. Found: C, 66.19; H, 8.63; N, 4.40. 1 H NMR (23 C, C6D6): d 8.50 (Dn1/2 ¼ 25 Hz), 5.06 (Dn1/2 ¼ 48 Hz), 1.99 (Dn1/2 ¼ 127 Hz). meff ¼ 1.98(9)mB (C6D6, 298K, Evans’ method). UV– * Sometimes it is necessary to physically separate the red crystals of (LtBu,iPr2)Ti¼NAr(Cl) from the intensely green microcrystals of (LtBu,iPr2)TiCl2. To obtain reproducible recrystallization results, it is highly recommended to have a homogeneous solution prior to cooling.

28

Complexes of Bulky b-Diketiminate Ligands

vis (toluene, 25 C): 344 nm (3780 M 1 cm 1). IR (Nujol, CaF2): 1363 (s), 1258 (m), 1212 (w), 1180 (w), 939 (w). mp 146(3) C (the color changes from green to reddish during the melting process). Properties Complex (LtBu,iPr2)TiCl2 (intense green) is indefinitely stable at 35 C and in the absence of oxidants or protic media. This complex is soluble in toluene, benzene, THF, and Et2O, but insoluble in pentane and hexane. Unlike (LtBu,iPr2)TiCl2(THF), (LtBu,iPr2)TiCl2 appears to be stable in CH2Cl2 over several hours at room temperature, but decomposition ensues after extended times. Related Compounds Complex (LtBu,iPr2)TiCl2 can be alkylated to the dimethyl derivative, (LtBu,iPr2) TiMe2, a precursor to the Ti(IV) complex (LtBu,iPr2)TiMe2(OTf) by AgOTf oxidation.12 The latter complex is a convenient synthon to the phosphinidene, (LtBu,iPr2) Ti¼P[Trip](Me),13 via the treatment with LiPH[Trip] (Trip ¼ 2,4,6-iPr3C6H2). Complex (LtBu,iPr2)TiCl2 can also be alkylated with 2 equiv of LiCH2tBu to afford (LtBu,iPr2)Ti(CH2tBu)2,12 a precursor to the four-coordinate alkylidene complex (LtBu,iPr2)Ti¼CHtBu(OTf).12 An alternative synthesis of (LtBu,iPr2)TiCl2 without formation of the imido impurity can be achieved using TiCl3 instead of TiCl3(THF)3 in toluene.12 The low yield of (LtBu,iPr2)TiCl2 (23%), however, coupled with the expense in using TiCl3 makes this process unattractive. C. SYNTHESIS OF (LMe,iPr2)VCl2 LiLtBu;iPr2 þ VCl3 ðTHFÞ3 ! ðLMe;iPr2 ÞVCl2 ðTHFÞ þ 2 THF þ LiCl ðLtBu;iPr2 ÞVCl2 ðTHFÞ ! ðLtBu;iPr2 ÞVCl2 þ THF Procedure The procedure for (LMe,iPr2)VCl2 is a slight modification of the literature method.6 VCl3(THF)314 (3.00 g, 0.008 mol) is slurried in 40 mL of THF and [LMe,iPr2Li]x (3.41 g, 0.008 mol) is dissolved in 30 mL of THF. Inside the glovebox, both solutions are loaded in a 350- or 500-mL heavy wall glass round-bottomed pressure vessel (Fig.1, vide supra, CHEMGLASS), which is securely sealed with a Teflon cap. After mixing, the color of the solution gradually changes to red-brown. The mixture is transferred out of the glovebox and refluxed with stirring at 90 C for 30 min, upon which the solution rapidly turns to deep brown-red. The solution is cooled to room temperature, and then the flask is brought into the glovebox and transferred to a Schlenk flask. The volatiles are removed under reduced pressure inside the glovebox to yield a red-brown solid. The flask is sealed with a glass

6. b-Diketiminate-Supported Titanium and Vanadium Dichloride

29

stopper, and then evacuated and brought out of the glovebox. The flask is then heated at 100 C for 45 min under dynamic vacuum on a Schlenk line. During the heating/vacuum process, the complex loses THF to afford a deep green solid. The flask is transferred into the glovebox, and the deep green mass is washed with 25 mL of hexane and then extracted with 200 mL of toluene. The toluene solution is filtered through a bed of Celite, rinsing the residue with 10 mL portions of toluene until the filtrate is almost colorless (approximately three portions). The volume of the deep green filtrate is reduced to 50 mL until a solid begins forming on the sides of the flask. The solution is capped with a rubber stopper and cooled to 35 C for 2 days to obtain bright green crystals of (LMe,iPr2)VCl2. After filtration, the green crystals are collected and dried under reduced pressure. The filtrate is then concentrated (25 mL) and stored at 35 C for 1 day to afford a second batch of product, which is dried under vacuum. The combined yield is 3.29 g (0.006 mol, 76% yield). 1

H NMR (23 C, C6D6): d 5.91 (Dn1/2 ¼ 123 Hz), 3.64 (Dn1/2 ¼ 561 Hz), 2.66 (Dn1/2 ¼ 194 Hz). meff ¼ 2.90(1)mB (C6D6, 298K, Evans’ method). UV–vis (toluene (e in M 1 cm 1)): 789 (260), 586 (287), 416 (2100), 319 (7973) nm. IR (Nujol, KBr plates) 1534 (m), 1340 (s), 1320 (s), 804 (m), 757 (w) cm 1. mp decomp. >200 C.6 Properties Complex LMe,iPr2VCl2 is a deep green material soluble in toluene, Et2O, benzene, and THF. It has properties similar to LMe,iPr2TiCl2(THF), being insoluble in hexane and pentane. The complex gradually decomposes in CH2Cl2. Complex LMe,iPr2VCl2 is readily oxidized by O2 and reacts rapidly with water to afford intractable products. Related Compounds Complex LMe,iPr2VCl2 can be readily alkylated with 2 equiv of LiMe, LinBu, and LiCH2tBu to afford the corresponding bis-alkyl complexes LMe,iPr2V(R)2 (R ¼ Me,6n Bu,6 CH2tBu15). Complex LMe,iPr2V(Me)2 is not as active catalyst as the titanium analogue for the polymerization of propene and 1-hexene when activated with B(C6F5)3.6 However, the alkyl derivative LMe,iPr2V(CH2tBu)2 is an excellent precursor to both vanadium(IV) alkylidene species15 and V(V) alkylidynes such as (LMe,iPr2)V:CtBu(OTf)16 and [(LMe,iPr2)V:CtBu(THF)][BPh4].16 The latter complexes are prepared by a stepwise one-electron oxidation, followed by alkylation with LiCH2SiMe3, and then another one-electron oxidation with AgX (X ¼ OTf or BPh4).16 Complex (LMe,iPr2)VCl2 is also a convenient precursor to terminal and neutral vanadium nitride complexes.17 Acknowledgments The authors thank Indiana University, Bloomington, the Camille and Henry Dreyfus Foundation (New Faculty and Teacher–Scholar Awards to D.J.M.), the Alfred P.

30

Complexes of Bulky b-Diketiminate Ligands

Sloan Foundation (fellowship to D.J.M.), and the U.S. National Science Foundation (CHE-0348941, PECASE Award to D.J.M.) for support to this research. References 1. A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen, and F. J. Timmers, Organometallics 15, 1518 (1996). 2. N. A. Jones, S. T. Liddle, C. Wilson, and P. L. Arnold, Organometallics 26, 755 (2007). 3. S. K. Sur, J. Magn. Reson. 82, 169 (1989). 4. D. F. Evans, J. Chem. Soc. 2003 (1959). 5. M. Stender, R. J. Wright, B. E. Eichler, J. Prust, M. M. Olmstead, H. W. Roesky, and P. P. Power, Dalton Trans. 3465 (2001). 6. P. H. M. Budzelaar, A. B. van Oort, and A. G. Orpen, Eur. J. Inorg. Chem. 1485 (1998). 7. F. Basuli, B. C. Bailey, J. Tomaszewski, J. C. Huffman, and D. J. Mindiola, J. Am. Chem. Soc. 125, 6052 (2003). 8. F. Basuli, D. Adhikari, J. C. Huffman, and D. J. Mindiola, J. Organomet. Chem. 692, 3115 (2007). 9. F. Basuli, B. C. Bailey, J. C. Huffman, and D. J. Mindiola, Chem. Commun. 1554 (2003). 10. B. C. Bailey, F. Basuli, J. C. Huffman, and D. J. Mindiola, Organometallics 25, 2725 (2006). 11. F. Basuli, R. L. Clark, B. C. Bailey, D. Brown, J. C. Huffman, and D. J. Mindiola, Chem. Commun. 2250 (2005). 12. F. Basuli, B. C. Bailey, L. A. Watson, J. Tomaszewski, J. C. Huffman, and D. J. Mindiola, Organometallics 24, 1886 (2005). 13. G. Zhao, F. Basuli, U. J. Kilgore, H. Fan, H. Aneetha, J. C. Huffman, G. Wu, and D. J. Mindiola, J. Am. Chem. Soc. 128, 13575 (2006). 14. L. E. Manzer, Inorg. Synth. 21, 135 (1982). 15. F. Basuli, U. J. Kilgore, X. Hu, K. Meyer, M. Pink, J. C. Huffman, and D. J. Mindiola, Angew. Chem., Int. Ed. 43, 3156 (2004). 16. F. Basuli, B. C. Bailey, D. Brown, J. Tomaszewski, J. C. Huffman, M.-H. Baik, and D. J. Mindiola, J. Am. Chem. Soc. 126, 10506 (2004). 17. B. L. Tran, M. Pink, X. Gao, H. Park, and D. J. Mindiola, J. Am. Chem. Soc. 132, 1458 (2010).

7. b-DIKETIMINATE-SUPPORTED VANADIUM AND CHROMIUM CHLORIDE COMPLEXES Submitted by CHULEEPORN PUTTNUAL, LEONARD A. MacADAMS, and KLAUS H. THEOPOLD Checked by YOSRA M. BADIEI† and TIMOTHY H. WARREN†

General Procedures All manipulations of compounds were carried out using standard Schlenk, vacuum line, and glovebox techniques. Pentane, diethyl ether, tetrahydrofuran, and toluene *

Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716. Department of Chemistry, Georgetown University, Washington, DC 20057-1227.

†

7. b-Diketiminate-Supported Vanadium and Chromium Chloride Complexes

31

were distilled from purple Na benzophenone ketyl solutions. C6D6 was predried  with sodium and stored under vacuum over 4 A molecular sieves. NMR spectra were referenced to the residual protons of the solvent (C6D5H ¼ 7.15 ppm, CDHCl2 ¼ 5.32 ppm). Molar magnetic susceptibilities were corrected for diamagnetism using Pascal constants. Butyllithium was purchased as a 1.6 M solution in hexane from Aldrich. VCl3 (anhydrous) and CrCl3 (anhydrous) were purchased from Strem. VCl3(THF)31 and CrCl3(THF)32 were prepared according to the literature procedures. HLMe,Me2 was prepared according to Budzelaar’s method (see Section 2A).3 A. SYNTHESIS OF LMe,Me2VCl2 HLMe;Me2 þ BuLi ! LiLMe;Me2 þ BuH LiLMe;Me2 þ VCl3 ðTHFÞ3 ! LMe;Me2 VCl2 ðTHFÞ þ LiCl þ 2 THF Procedure A solution of 10.0 g (32.6 mmol) of HLMe,Me2 in 100 mL of diethyl ether is prepared in a 250-mL Schlenk flask. The solution is cooled to 30 C and then treated with 20.42 mL (32.6 mmol) of 1.6 M n-butyllithium in hexane. The mixture is allowed to warm to room temperature and the yellow solution thus obtained is added to a 500-mL flask containing a red slurry of 12.18 g (32.6 mmol) of VCl3(THF)3 in 200 mL of THF. The resulting dark red-brown solution is stirred overnight at room temperature giving a dark green solution. The solution is evaporated to dryness; the residue is triturated three times with 20 mL of diethyl ether to give a green solid, discarding the ether. The residue is then extracted three times with toluene totaling ca. 200 mL, and the combined extract is filtered through Celite, rinsing with ca. 10 mL of toluene. The resultant solution is concentrated to approximately one-third of its original volume and left to crystallize at 30 C to afford red-brown crystals. Yield: 10.50 g (75%). Anal. Calcd. for C21H25N2Cl2V: C, 59.03%; H, 5.90%; N, 6.49%; Cl, 16.59%. Found: C, 59.06%; H, 5.85%; N, 6.42%; Cl, 16.33%. 1 H NMR (CD2Cl2): d 8.1, 7.5 (vb, 22H), 2.5 (b, 3H). IR (KBr): 3015 (w), 2918 (m), 1534 (s), 1467 (m), 1376 (m), 1323 (s), 1234 (m), 1170 (w), 1094 (w), 1020 (w), 866 (w), 772 (s), 416 (m) cm 1. EI-MS m/z (%): 426.0 (100) [M þ ], 391.1 (8.3)[M þ Cl]. UV–vis (toluene): lmax (e in M 1 cm 1) 415 (1773), 561 (409), 758 nm (460). meff ¼ 3.1 (1)mB (294K). mp 268–270 C.

32

Complexes of Bulky b-Diketiminate Ligands

Properties LMe,Me2VCl2 is soluble in THF, toluene, and dichloromethane but essentially insoluble in ether and pentane. In the b-diketiminato complexes LVCl2, the nature of the N-aryl substituents determines the affinity of the complex for THF. For instance, the parent N-phenyl-substituted b-diketiminate is isolated as a bis(THF) solvate LMe,Me2VCl2(THF)2,4 whereas LMe,Me2VCl2, LMe,Me3VCl2,3 and LMe, iPr2 VCl23 may be isolated THF-free. As outlined in the entry for LMe,iPr2VCl2 (described herein), b-diketiminato vanadium dihalide complexes have been explored as precatalysts for a-olefin polymerization and may be alkylated to give dialkyls LVR2. B. SYNTHESIS OF LMe,Me2CrCl2(THF)2 HLMe;Me2 þ BuLi ! LiLMe;Me2 þ BuH LiLMe;Me2 þ CrCl3 ðTHFÞ3 ! LMe;Me2 CrCl2 ðTHFÞ þ LiCl þ 2 THF Procedure HLMe,Me2 (1.0 g, 3.27 mmol) is dissolved in 50 mL of THF and the solution was cooled to 30 C. n-Butyllithium (2.0 mL of 1.6 M in hexanes, 3.27 mmol) is slowly added to this solution, and this mixture is stirred for another 30 min and allowed to warm to room temperature. The resultant solution of LiLMe,Me2 is then slowly added over 3 h at room temperature to a slurry of CrCl3(THF)3 (1.224 g, 3.27 mmol) in 150 mL of THF. The color of the solution changes from purple to red-brown. After stirring the solution at room temperature overnight, the THF is removed and the solid is extracted with three 30-mL portions of toluene. The solution is then filtered through Celite, rinsing with ca. 20 mL toluene. The toluene is then removed in vacuo and the solid is dissolved in ca. 40 mL THF and refiltered through Celite. The resulting THF solution is concentrated to 20 mL in vacuo and allowed to crystallize overnight at 30 C. A dark red microcrystalline powder is isolated by filtration. After washing with ca. 5 mL cold THF and drying under vacuum, 1.45 g (76%) of the product is isolated. Anal. Calcd. for C29H41N2O2CrCl2: C, 60.84%; H, 7.22%; N, 4.89%. Found: C, 60.71%; H, 7.03%; N, 5.38%. 1 H NMR (C6D6): d 40.7 (vb, 6H), 13.3 (vb, 4H), 9.4 (vb, 4H), 3.8 (b, 8H), 1.4 (b, 8H), 4.2 (vb, 2H) ppm. IR (KBr): 3050 (w), 3014 (m), 2965 (s), 2925 (s), 2869 (s), 1520 (vs), 1459 (vs), 1448 (vs), 1377 (vs), 1259 (m), 1242 (m), 1177 (s), 1096 (m), 1015 (m), 1005 (m), 879 (s), 850 (s), 762 (s) cm 1. UV–vis (Et2O): lmax (e in M 1 cm 1) 656 (224), 506 (815), 476 (945),

7. b-Diketiminate-Supported Vanadium and Chromium Chloride Complexes

33

407 (5300). meff ¼ 4.0(1)mB (294K). mp 208–209 C. Mass spectrum m/z (%): 427 2THF], 392 (17.3) [M þ Cl, 2THF], 356 (17.6) [M þ 2Cl, (4.14) [M þ 2THF].

Properties LMe,Me2CrCl2(THF)2 is soluble in THF and partially soluble in toluene, benzene, and ether. The solution is red-brown in THF, toluene, and benzene, but changes to a yellow color in ether.

Related Compounds b-Diketiminato chromium halide and alkyl complexes have been explored as precatalysts for alkene polymerization.4–7 For instance, LMe,Me2CrCl2(THF)2 reacts with alkyllithium reagents to give LMe,Me2CrMe2(THF) and LMe,Me2Cr (CH2SiMe3)2.7 These dialkyls may be converted to alkyl cations such as [LMe, iPr2 Cr(CH2SiMe3)(OEt2)] þ that serves as a living ethylene polymerization catalyst.7 In addition, hydrogenation of LMe,Me2Cr(CH2SiMe3)2 produces the stable alkyl hydride complex [LMe,Me2Cr]2(m-CH2SiMe3)(m-H).8 The bulkier LMe,iPr2 ligand has been used to prepare the highly reactive synthons to the two-coordinate LMe,iPr2Cr fragment [LMe,iPr2Cr]2(m-h2:h2-N2)9 and [LMe,iPr2Cr]2(m-h6:h6-toluene),10 which participate in a variety of interesting reactions such as oxidation by O2 to give the d1 dioxo complex LMe,iPr2Cr(O)2. References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

L. E. Manzer, Inorg. Synth. 21, 135 (1982). W. Herwig and H. Zeiss, J. Org. Chem. 23, 1404 (1958). P. H. M. Budzelaar, A. B. van Oort, and A. G. Orpen, Eur. J. Inorg. Chem. 1485 (1998). W.-K. Kim, M. J. Fevola, L. M. Liable-Sands, A. L. Rheingold, and K. H. Theopold, Organometallics 17, 4541 (1998). V. C. Gibson, C. Newton, C. Redshaw, G. A. Solan, A. J. P. White, and D. J. Williams, Eur. J. Inorg. Chem. 1895 (2001). L. A. MacAdams, W.-K. Kim, L. M. Liable-Sands, I. A. Guzei, A. L. Rheingold, and K. H. Theopold, Organometallics 21, 952 (2002). L. A. MacAdams, G. P. Buffone, C. D. Incarvito, A. L. Rheingold, and K. H. Theopold, J. Am. Chem. Soc. 127, 1082 (2005). L. A. MacAdams, G. P. Buffone, D. C. Incarvito, H. A. Golen, A. L. Rheingold, and K. H. Theopold, Chem. Commun. 1164 (2003). W. H. Monillas, G. P. A. Yap, L. A. MacAdams, and K. H. Theopold, J. Am. Chem. Soc. 129, 8090 (2007). Y.-C. Tsai, P.-Y. Wang, S.-A. Chen, and J.-M. Chen, J. Am. Chem. Soc. 129, 8066 (2007).

34

Complexes of Bulky b-Diketiminate Ligands

8. b-DIKETIMINATE-SUPPORTED MANGANESE AND ZINC COMPLEXES Submitted by HERBERT W. ROESKY Checked by MATTHEW S. VARONKA and TIMOTHY H. WARREN†

A two-step procedure is employed based on the literature procedure for LMe, iPr2 MnI(THF), which first generates the potassium salt KLMe,iPr2 prior to its reaction with MnI2.1 The preparation of the potassium salt of the b-diketimine HLMe,iPr2 was first reported by Mair and coworkers from HLMe,iPr2 and KN(SiMe3)2 in relatively low yield (27%).2 Winter and coworkers have reported a related THF adduct from KH.3 Here, the same reagents in diethyl ether give a base-free potassium salt that was used to introduce LMe,iPr2 into manganese and zinc complexes. General Procedures All reactions were performed using standard Schlenk and drybox techniques. All the solvents except dichloromethane (P4O10) were distilled from sodium under dry nitrogen. 12 M HCl, MnI2, ZnI2, and BuLi in hexane were purchased from Aldrich. A. LMe,iPr2MnI(THF)

HLMe;iPr2 þ KH ! KLMe;iPr2 þ H2 KLMe;iPr2 þ MnI2 þ THF ! LMe;iPr2 MnIðTHFÞ þ KI & Caution. Air-free procedures are required for use of potassium hydride, which can explosively generate hydrogen gas upon uncontrolled hydrolysis. Hydrogen gas is generated in the procedure and should not be performed in a sealed flask. Step 1: A suspension of KH (0.18 g, 4.5 mmol) and HLMe,iPr2 (1.67 g, 4.00 mmol) in diethyl ether (50 mL) is stirred at room temperature for 3 days. After filtration, the light yellow filtrate is concentrated to ca. 10 mL and stored at 26 C for 24 h to afford crystalline solid. Yield: 1.59 g (87%). *

Institut f€ ur Anorganische Chemie, Universit€at Go¨ttingen, D-37077 Go¨ttingen, Germany. Department of Chemistry, Georgetown University, Washington, DC 20057-1227.

†

8. b-Diketiminate-Supported Manganese and Zinc Complexes

35

1

H NMR (C6D6): d 7.08 (d, J ¼ 8.0 Hz, 4H, ArH), 6.96 (t, J ¼ 8.0 Hz, 2H, ArH), 4.74 (s, 1H, CH), 3.29 (sept, J ¼ 7.2 Hz, 4H, CH(CH3)2), 3.29 (sept, J ¼ 7.2 Hz, 4H, CH(CH3)2), 1.81 (s, 6H, CH3), 1.19 (d, J ¼ 6.8 Hz, 12H, CH(CH3)2), 1.00 (d, J ¼ 6.8 Hz, 12H, CH(CH3)2).

Step 2: A solution of KLMe,iPr2 (0.91 g, 2.0 mmol) in THF (10 mL) is added to a suspension of MnI2 (0.62 g, 2.0 mmol) in THF (35 mL) at 78 C. The mixture is allowed to warm to room temperature and stirred for 14 h. The precipitate is removed by filtration. The yellow filtrate is concentrated to ca. 5 mL and stored at 26 C for 24 h to give yellow crystals. Yield: 1.17 g (87%).* Anal. Calcd. for C33H49IMnN2O (670.84): C, 59.03; H, 7.30; N, 4.17. Found: C, 58.95; H, 7.24; N, 4.16. EI-MS: m/z (%) 599 (100) [LMnI] þ . UV–vis (THF, nm (cm 1 M 1)) 439 (93), 461 (64). mp 379–381 C. IR (KBr, Nujol mull, cm 1): 1624 (w), 1552 (w), 1520 (m), 1314 (m), 1262 (m), 1174 (w), 1100 (w), 1024 (m), 935 (w), 870 (w), 852 (w), 794 (m), 757 (w), 721 (w), 600 (vw), 524 (w), 468 (vw). Properties LMe,iPr2MnI(THF) is soluble in THF and toluene and sparingly soluble in Et2O and n-pentane. The bound THF ligand may be readily removed by refluxing in toluene (see below) and may be displaced by other Lewis bases such as a N-heterocyclic carbene ligand.1 B. THE THF-FREE DIMER (LMe,iPr2MnI)2 LMe;iPr2 MnIðTHFÞ ! LMe;iPr2 MnI þ THF A solution of LMe,iPr2MnI(THF) (1.34 g, 2 mmol) in toluene (40 mL) is refluxed for 0.5 h. All volatiles are removed in vacuo and bright yellow microcrystals are obtained. Yield: 1.15 g (96%). Anal. Calcd. for C58H82I2Mn2N4 (1197.68): C, 58.11; H, 6.84; N, 4.67. Found: C, 58.34; H, 6.92; N, 4.85. EI-MS: m/z 599 (100) [LMnI] þ . IR (KBr, Nujol mull, cm 1): 1657 (w), 1625 (w), 1552 (w), 1262 (m), 1097 (m), 1023 (m), 875 (w), 800 (m), 722 (w), 659 (w), 536 (w), 468 (w) cm 1. mp 271–273 C (dec). Properties and Related Compounds The product is soluble in toluene and insoluble in Et2O and pentane. This dimeric bdiketiminato manganese iodide complex as well as its chloride-bridged relative *

The checkers obtained yellow crystals from one crystallization with a yield of 53%.

36

Complexes of Bulky b-Diketiminate Ligands

(LMe,iPr2MnCl)24 can be alkylated with MeLi and arylated with PhLi to give the dinuclear (LMe,iPr2Mn)2(m-Me)2 or the three-coordinate LMe,iPr2MnPh.4,5. A related trinuclear species LMe,iPr2Mn(m-Cl)2Mn(m-Cl)2MnLMe,iPr2 undergoes related reaction with allylmagnesium chloride to yield the four-coordinate LMe,iPr2Mn (CH2CH¼CH2)(THF) and with phenylethynyl lithium to give (LMe,iPr2Mn)2(mCCPh)2.6 Reduction of (LMe,iPr2MnI)2 yields the highly reactive ferromagnetically  coupled dimer (LMe,iPr2Mn)2 with a Mn–Mn distance of 2.721(1) A.7,8 This novel MnI–MnI dimer reacts with dioxygen to form the bis(m-oxo) species (LMe, iPr2 Mn)2(m-O)2.7 C. LMe,iPr2ZnCl2Li(OEt2)2 HLMe;iPr2 þ BuLi þ Et2 O ! LiLMe;iPr2 ðEt2 OÞ þ BuH LiLMe;iPr2 ðEt2 OÞ þ ZnCl2 þ Et2 O ! LMe;iPr2 ZnCl2 LiðEt2 OÞ þ LiCl & Caution. Butyllithium is pyrophoric in air and should be handled exclusively under dry nitrogen or argon. This two-step procedure uses the ether adduct of the lithium salt LMe,iPr2Li(OEt2)9,10 in the reaction with ZnCl2 to give the ‘‘ate’’ complex LMe,iPr2ZnCl2Li(OEt2)2.12 Step 1: HLMe,iPr2 (8.00 g, 19.1 mmol) is dissolved in rapidly stirred Et2O (70 mL), and the resulting solution is treated with 12.0 mL of a 1.6 M n-BuLi solution in hexane. Upon completion of the addition, the solution is allowed to warm to room temperature and stirred for 12 h. The solution is concentrated to approximately 20 mL under reduced pressure until the product precipitates, which redissolves with mild heating. Cooling for 24 h at ca. 20 C affords LMe,iPr2Li(OEt2) as colorless crystals. mp 138–139 C. Yields range between 75% and 90%. 1

H NMR (CDCl3): d 7.02 (m, 6H, ArH), 4.62 (s, 1H, CH), 3.13 (sept, J ¼ 6.8 Hz, 4H, CH(CH3)2), 2.92 (quad, J ¼ 6.8 Hz, 4H, ether-CH2), 1.72 (s, 6H, CH3), 1.21 (d, J ¼ 7.2 Hz, 12H, CH(CH3)2), 1.07 (d, J ¼ 7.2 Hz, 12H, CH(CH3)2), 0.61 (t, J ¼ 6.8 Hz, 6H, ether-CH3). 7 Li NMR (C6D6): d 1.61.

Step 2: To a suspension of ZnCl2 (395 mg, 2.90 mmol) in Et2O (10 mL) is slowly added a solution of LMe,iPr2LiOEt2 (1.44 g. 2.90 mmol) in Et2O (10 mL) at 35 C. The mixture is allowed to warm to room temperature and then stirred for additional 3 h and then filtered. The solution is concentrated to 10 mL and cooled overnight at 35 C to yield colorless crystals. Yield: 1.36 g (67%). * The checkers note that closely related procedures have been reported to give the halide-free monomer LMe,iPr2ZnCl, though two attempts at checking gave only the LiCl adduct LMe,iPr2ZnCl2Li(OEt2)2 in comparable yields to that described above.

8. b-Diketiminate-Supported Manganese and Zinc Complexes

37

Anal. Calcd. for C37H61Cl2LiN2O2Zn (709.15): C, 62.67; H, 8.67; N, 3.95. Found: C, 62.46; H, 8.81; N, 4.19. 1 H NMR (CDCl3): d 7.17 (m, 6H, ArH), 5.10 (s, 1H, CH), 3.47 (quad, J ¼ 7.2 Hz, 8H, ether-CH2), 2.98 (sept, J ¼ 6.8 Hz, 4H, CH (CH3)2), 1.81 (s, 6H, CH3), 1.25 (d, J ¼ 6.8 Hz, 12H, CH(CH3)2), 1.20 (t, J ¼ 7.2 Hz, 12H, ether-CH3), 1.16 (d, J ¼ 6.8 Hz, 12H, CH(CH3)2); 13 C NMR (C6D6): d 170.1, 142.1, 141.5, 126.3, 123.6, 95.3, 65.8, 28.2, 24.2, 23.6, 23.2, 15.2. Properties LMe,iPr2Li(OEt2) is readily soluble in ether, THF, and hydrocarbons as well as halogenated solvents such as CH2Cl2. LMe,iPr2ZnCl2Li(OEt2)2 is soluble in THF, ether, and aromatic solvents, sparingly soluble in CH2Cl2, and essentially insoluble in pentane. The Et2O coordinated to Li is somewhat labile. Titration of the solid with other solvents such as CDCl3 results in a gradual loss of Et2O. This b-diketiminate has been reported to be isolated as the three-coordinate complex LMe,iPr2ZnCl via careful crystallization.11,12 Related Compounds Both LMe,iPr2ZnCl and LMe,iPr2ZnCl2Li(OEt2)2 serve as platforms for subsequent modification. Three-coordinate alkyl complexes LMe,iPr2Zn-R may be formed by alkylation with alkyllithium reagents. Monoethyl complexes may also be prepared by use of ZnEt2 with the free ligand HL.13,14 Reaction of LMe,Me2ZnMewith Me3SnF gives the fluoride-bridged dimer (LMe,Me2Zn)2(m-F)2, which can be converted to the hydride-bridged dimer (LMe,Me2Zn)2(m-H)2 upon reaction with Et3SiH.15 The lithium halide-bridged adducts LZnX2Li(OEt2) are also synthetically useful in the preparation of thiolate-bridged dimers (LMe,Me2Zn)2(m-SR)2.16 b-Diketiminato zinc complexes have been investigated as catalysts for epoxide/CO2 copolymerization13,14,17–19 and ring-opening lactide polymerization.20–23 The related LMe, iPr2 ZnI2Li(OEt2)2 can be reduced by potassium metal to give the unusual ZnI–ZnI dimer (LMe,iPr2Zn)2 with a Zn Zn bond distance of 2.3586(7) A.24 References 1. J. Chai, H. Zhu, K. Most, H. W. Roesky, D. Vidovic, H.-G. Schmidt, and M. Noltemeyer, Eur. J. Inorg. Chem. 4332 (2003). 2. W. Clegg, E. K. Cope, A. J. Edwards, and F. S. Mair, Inorg. Chem. 37, 2317 (1998). 3. H. M. El-Kaderi, M. J. Heeg, and C. H. Winter, Polyhedron 25, 224 (2006). 4. J. Chai, H. Zhu, H. W. Roesky, C. He, H.-G. Schmidt, and M. Noltemeyer, Organometallics 23, 3284 (2004). 5. J. Chai, H. Zhu, H. Fan, H. W. Roesky, and J. Magull, Organometallics 23, 1177 (2004). 6. J. Chai, H. Zhu, H. W. Roesky, Z. Yang, V. Jancik, R. Herbst-Irmer, H.-G. Schmidt, and M. Noltemeyer, Organometallics 23, 5003 (2004). 7. J. Chai, H. Zhu, A. C. St€uckl, H. W. Roesky, J. Magull, A. Bencini, A. Caneschi, and D. Gatteschi, J. Am. Chem. Soc. 127, 9201 (2005).

38

Complexes of Bulky b-Diketiminate Ligands

8. L. Sorace, C. Golze, D. Gatteschi, A. Bencini, H. W. Roesky, J. Chai, and A. C. St€uckl, Inorg. Chem. 45, 395 (2006). 9. M. Stender, R. J. Wright, B. E. Eichler, J. Prust, M. M. Olmstead, H. W. Roesky, and P. P. Power, J. Chem. Soc., Dalton Trans. 3465 (2001). 10. Y. Ding, H. W. Roesky, M. Noltemeyer, H.-G. Schmidt, and P. P. Power, Organometallics 20, 1190 (2001). 11. J. Prust, A. Stasch, W. Zheng, H. W. Roesky, E. Alexopoulos, I. Uso´n, D. Bo¨hler, and T. Schuchardt, Organometallics 20, 3825 (2001). 12. J. Prust, H. Hohmeister, A. Stasch, H. W. Roesky, J. Magull, E. Alexopoulos, I. Uso´n, H. G. Schmidt, and M. Noltemeyer, Eur. J. Inorg. Chem. 2156 (2002). 13. M. Cheng, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 120, 11018 (1998). 14. M. Cheng, D. R. Moore, J. J. Reczek, B. M. Chamberlain, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 123, 8738 (2001). 15. H. Hao, C. Cui, H. W. Roesky, G. Bai, H.-G. Schmidt, and M. Noltemeyer, Chem. Commun. 1118 (2001). 16. M. S. Varonka and T. H. Warren, Inorg. Chim. Acta 360, 317 (2007). 17. S. D. Allen, D. R. Moore, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 124, 14284 (2002). 18. D. R. Moore, M. Cheng, E. B. Lobkovsky, and G. W. Coates, Angew. Chem., Int. Ed. 41, 2599 (2002). 19. C. M. Byrne, S. D. Allen, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 126, 11404 (2004). 20. M. Cheng, A. B. Attygalle, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 121, 11583 (1999). 21. B. M. Chamberlain, M. Cheng, D. R. Moore, T. M. Ovitt, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 123, 3229 (2001). 22. L. R. Rieth, D. R. Moore, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 124, 15239 (2002). 23. A. P. Dove, V. C. Gibson, E. L. Marshall, A. J. P. White, and D. J. Williams, Dalton Trans. 570 (2004). 24. Y. Wang, B. Quillian, P. Wei, H. Wang, X.-J. Yang, Y. Xie, R. B. King, P. v. R. Schleyer, H. F. SchaefferIII, and G. H. Robinson, J. Am. Chem. Soc. 127, 11944 (2005).

9. IRON 2,4-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)PENTYL CHLORIDE (LMe,iPr2FeCl) Submitted by BRYAN D. STUBBERT and PATRICK L. HOLLAND Checked by DEBASHIS ADHIKARI† and DANIEL J. MINDIOLA†

General Techniques All manipulations were performed under a nitrogen atmosphere by standard Schlenk techniques or in a glovebox maintained at or below 1 ppm of O2 and

*

Department of Chemistry, University of Rochester, Rochester, NY 14627. Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405.

†

9. Iron 2,4-BIS-(2,6-Diisopropylphenylimido)Pently Chloride (LMe,iPr2FeCl)

39

Figure 1. Reaction flask used in this procedure.

H2O. Glassware was dried at 150 C overnight. Pentane and toluene were purified by passing through activated alumina and Q-5 columns from Glass Contour Co. Deuterated THF was first dried over CaH2, then over Na/benzophenone, and then vacuum transferred into a storage container. Before use, an aliquot of each solvent was tested with a drop of sodium benzophenone ketyl in THF solution. Celite was dried overnight at 200 C under vacuum. The iron starting material FeCl2(THF)1.5 was synthesized by the method of Kern,1 by heating anhydrous FeCl22 to reflux overnight in THF and subsequently removing volatile materials in vacuo.* [LMe,iPr2Li]x was prepared using the method described herein. FeCl2 ðTHFÞ1:5 þ ½LMe;iPr2 LiŠx ! LMe;iPr2 Feðm-ClÞ2 FeLMe;iPr2 þ LiCl Procedure In a glovebox, a 100-mL thick-walled flask with a resealable Teflon valve (Fig. 1) is charged with a magnetic stir bar and [LMe,iPr2Li]x (2.38 g, 5.60 mmol). Toluene (40 mL) is added to dissolve the solid, forming a pale yellow solution, and while stirring at 25 C, solid FeCl2(THF)1.5 (1.32 g, 5.72 mmol) is added to the solution in several portions. An immediate color change from pale yellow to light red is observed during the FeCl2(THF)1.5 addition. The flask is then sealed and moved from the glovebox to the Schlenk line where it is heated in an oil bath, gradually raised from 25 to 100 C. After 18 h, the red-orange suspension is allowed to cool and is evaporated to dryness. The oil bath is then heated to 40 C, and the orange solid is *

The checkers prepared FeCl2(THF)1.5 by Sohxlet extraction of anhydrous FeCl2 with THF over the course of 2 weeks.

40

Complexes of Bulky b-Diketiminate Ligands

dried in vacuo for an additional 30–60 min to ensure complete removal of THF. The flask is then returned to the glovebox, and the solids are washed with pentane (3  10 mL) to remove unreacted LiLMe,iPr. The orange powder obtained after drying this material in vacuo, [LMe,iPrFeCl]22LiCl, is normally recovered in 95% yield and is commonly used in later syntheses without further purification (because later steps typically involve pentane extractions, the LiCl is filtered off at that stage). Note: Contact of [LMe,iPrFeCl]22LiCl with THF or Et2O results in the formation of the etherate complexes LMe,iPrFeCl2Li(THF)2 and LMe,iPrFeCl2Li(Et2O)2, which may not be suitable for some later syntheses. The etherate complexes can be desolvated, regenerating [LMe,iPrFeCl]22LiCl, by dissolving the yellow solids in toluene and heating at 100 C for 12 h and evacuating to dryness. The by-product LiCl can be removed by Soxhlet extraction. The insoluble orange powder obtained above is slurried in pentane (3  20 mL) and collected by gravity filtration in a glass thimble consisting of a coarse glass frit with a 0.5-cm pad of predried Celite. The thimble containing the washed orange solid is then placed in the Soxhlet extractor fitted with a 200-mL round-bottomed flask containing a large magnetic stir bar and toluene (150 mL) on the lower end and a condenser with a resealable Teflon valve. (Note: It is beneficial to measure the antechamber and assembled Soxhlet extraction apparatus prior to loading in the glovebox, because the assembled apparatus may be quite long. If the assembled apparatus is too long, the condenser can be attached to the flask outside the box with a vigorous flow of N2). Under a N2 atmosphere on the Schlenk line, the apparatus is heated in a 140 C oil bath. Most of the LiCl-free material is extracted into hot toluene in 3–4 h; however, completely colorless extracts are not observed until >12 h. After 24 h, the red suspension is evacuated to dryness, leaving a solid orange residue. In the glovebox, the residue is washed with pentane (3  10 mL) and dried in vacuo, affording LiCl-free [LMe,iPrFeCl]2 in 82% yield (2.34 g, 2.30 mmol). Purity is determined by 1 H NMR spectroscopy. 1

H NMR (THF-d8): d 17.6 (4H), 4.9 (12H), 3.3 (4H), 67.9 (6H), 78.9 (1H).

6.8 (12H),

38.3 (2H),

Properties [LMe,iPr2FeCl]2 is insoluble in alkane solvents, poorly soluble in Et2O and toluene, and soluble in THF. It reacts slowly with CH2Cl2. Additional characterization in noncoordinating solvents is limited by low solubility. It is sensitive to air and moisture. Related Compounds This compound is a precursor to a wide variety of three- and four-coordinate iron(II) complexes, including alkyl, aryl, hydride, sulfido, amido, and fluoride

10. Iron 2,2,6,6-Tetramethyl-3,5-BIS-(2,6-Diisopropylphenylimido)Heptyl

41

complexes.3 Abstraction of chloride with borane4 gives cationic iron(II) complexes with weak coordination of solvent or counterion. Reduction to an iron(I) dinitrogen complex provides a pathway to iron(I) alkyne, alkene, carbonyl, isocyanide, arene, and phosphine complexes, as well as a reactive iron(III) imido complex.3 Acknowledgments This work was supported by the National Science Foundation (CHE-0112658) and the Alfred P. Sloan Foundation (Research Fellowship). References 1. 2. 3. 4.

R. J. Kern, J. Inorg. Nucl. Chem. 24, 1105 (1962). G. Winter, Inorg. Synth. 14, 101 (1973). P. L. Holland, Acc. Chem. Res. 41, 905 (2008). T. J. J. Sciarone, A. Meetsma, B. Hessen, and J. H. Teuben, Chem. Commun. 1580 (2002).

10. IRON 2,2,6,6-TETRAMETHYL-3,5-BIS-(2,6DIISOPROPYLPHENYLIMIDO)HEPTYL CHLORIDE (LtBu,iPr2FeCl) Submitted by KAREN P. CHIANG and PATRICK L. HOLLAND Checked by DEBASHIS ADHIKARI† and DANIEL J. MINDIOLA†

General Techniques All manipulations were performed under a nitrogen atmosphere by standard Schlenk techniques or in a glovebox maintained at or below 1 ppm of O2 and H2O. Glassware was dried at 150 C overnight. NMR spectra are referenced to residual C6D5H at 7.16 ppm. Pentane and toluene were purified by passing through activated alumina and Q-5 columns from Glass Contour Co. Deuterated benzene was first dried over CaH2, then over Na/benzophenone, and then vacuum transferred into a storage container. Before use, an aliquot of each solvent was tested with a drop of sodium benzophenone ketyl in THF solution. Celite was dried overnight at 200 C under vacuum. The iron starting material FeCl2(THF)1.5 was synthesized by the method of Kern,1 by heating a THF slurry of anhydrous FeCl22 *

Department of Chemistry, University of Rochester, Rochester, NY 14627. Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405.

†

42

Complexes of Bulky b-Diketiminate Ligands

at reflux overnight and subsequently removing volatile materials in vacuo.* KLtBu;iPr2 þ FeCl2 ðTHFÞ1:5 ! LtBu;iPr2 FeCl Procedure Solid KLtBu,iPr2 (0.50 g, 0.919 mmol), FeCl2(THF)1.5 (0.2022 g, 0.919 mmol), and toluene (25 mL) are added to a 150-mL Schlenk flask (see Fig. 1 in Section 9). The charged flask is removed from the glovebox, and the reaction mixture is heated in an oil bath at 100 C for 18 h during which time it turns very dark red in color. The solution is then cooled to room temperature, returned to the glovebox, and filtered through Celite.The filtrateis concentrated to 8 mL, whereuponsome red solidbegins to form. The sample is warmed to ca. 40 C to redissolve the solid, and slowly cooled to 35 C overnight to afford dark red crystals. The supernatant is decanted and the red solid is washed with 2 mL of pentane to remove trace LtBu,iPr2H, leaving LtBu, iPr2 FeCl (0.5306 g, 97%). The overall purity is best gauged by UV–vis spectroscopy. UV–vis (toluene): 559 nm (626 M 1 cm 1). 1 H NMR (C6D6, 500 MHz): d 104 (s, 1H, a-H), 42 (s, 18H, tBu), 2.6 (s, 4H, m-aryl), 27 (s, 12H, iPr methyl), 108 (s, 4H, iPr methine), 111 (s, 12H, iPr methyl), 115 (s, 2H, p-aryl). Trace water results in a small amount of LtBu,iPrH, which is observed as white solid and appears in the 1 H NMR spectrum at 1–2 ppm. Properties LtBu,iPrFeCl is very soluble in THF and toluene, somewhat soluble in diethyl ether, and poorly soluble in pentane. It decomposes in CH2Cl2 in a few hours. It is extremely sensitive to moisture and air. Coordinating solvents such as THF and acetonitrile form yellow 1 : 1 adducts. Related Compounds This compound is a precursor to a wide variety of three- and four-coordinate iron (II) complexes, including alkyl, aryl, hydride, oxo, hydroxo, amido, and fluoride complexes.3,4 Reduction to an iron(I) dinitrogen complex provides a pathway to iron(I) complexes.4 Acknowledgments This work was supported by the National Science Foundation (CHE-0112658) and the Alfred P. Sloan Foundation (Research Fellowship). *

The checkers prepared FeCl2(THF)1.5 through a Soxhlet extraction of anhydrous FeCl2 with THF over 2 weeks.

11. Cobalt 2,2,6,6-Tetramethyl-3,5-Bis-(2,6-Diisopropylphenylimido)

43

References 1. R. J. Kern, J. Inorg. Nucl. Chem. 24, 1105 (1962). 2. G. Winter, Inorg. Synth. 14, 101 (1973). 3. V. C. Gibson, E. L. Marshall, D. Navarro-Llobet, A. J. P. White, and D. J. Williams, J. Chem. Soc., Dalton Trans. 4321 (2002). 4. P. L. Holland, Acc. Chem. Res. 41, 905 (2008).

11. COBALT 2,2,6,6-TETRAMETHYL-3,5-BIS-(2,6DIISOPROPYLPHENYLIMIDO)HEPTYL CHLORIDE (LtBu,iPr2CoCl) Submitted by KEYING DING, THOMAS R. DUGAN, and PATRICK L. HOLLAND Checked by DEBASHIS ADHIKARI† and DANIEL J. MINDIOLA†

The following reaction was originally conducted in THF solution using LiLtBu,iPr2, in which case the product is LtBu,iPr2Co(m-Cl)2Li(ether)2, which is four-coordinate at cobalt and has mixed coordination of Et2O and THF at the lithium ion.1 By using TlLtBu,iPr2 instead as the diketiminate source, the authors obtained the threecoordinate LtBu,iPr2CoCl. Here, the lithium salt is used but in hot toluene, the LiCl precipitates, and the three-coordinate monomer is obtained. This method eliminates the need for using the thallium salt.

General Procedures Manipulations were performed under a nitrogen atmosphere by standard Schlenk techniques or in a glovebox maintained at or below 1 ppm of O2 and H2O. Glassware was dried at 150 C overnight. NMR spectra are referenced to residual C6D5H at 7.16 ppm. Pentane and toluene were purified by passing through activated alumina and Q-5 columns from Glass Contour Co. Deuterated benzene was first dried over CaH2, then over Na/benzophenone, and then vacuum transferred into a storage container. Before use, an aliquot of each solvent was tested with a drop of sodium benzophenone ketyl in THF solution. Celite was dried overnight at 200 C under vacuum. The cobalt starting material CoCl2(THF)1.5 was synthesized by the method of Kern,2 by heating anhydrous CoCl2 (Sigma) to reflux overnight in THF and subsequently removing volatile materials in vacuo. *

Department of Chemistry, University of Rochester, Rochester, NY 14627. Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405.

†

44

Complexes of Bulky b-Diketiminate Ligands

LtBu;iPr2 LiðTHFÞ þ CoCl2 ðTHFÞ1:5 ! LtBu;iPr2 CoCl þ LiCl Procedure In the glovebox, blue CoCl2(THF)1.51 (705 mg, 2.96 mmol) is added to a 500-mL resealable flask (see Fig. 1 in Section 9) containing a pale yellow solution of LtBu, iPr2 Li(THF) (1.72 g, 2.96 mmol) in toluene (100 mL) and a stir bar, causing a slow color change to blue-brown. The flask is sealed, taken out of the glovebox, and heated in an oil bath, which is gradually heated to 100 C. After stirring for 18 h, the flask is returned to the glovebox, and the brown mixture is filtered through 1 cm of Celite.* The filtrate is concentrated to 40 mL and cooled at 35 C for 1 day to give brown-purple crystals. The supernatant solution is removed and the crystals are dried under vacuum to give 1.23 g of a brown-purple solid. Reducing the volume of the supernatant solution to 18 mL, adding 10 mL of pentane, and cooling to 35 C yields 0.25 g of additional crystals. The combined solids are washed with pentane to remove traces of LtBu,iPr2Li(THF) and LtBu,iPrH. Combined yield: 84%. H NMR (400 MHz, C6D6): d 59.9 (4H, m-aryl), 27.2 (18H, tBu), 2.7 (12H, iPr methyl), 45.4 (2H, p-aryl), 56.5 (4H, iPr methine), 83.0 (12H, iPr methyl), 89.3 (1H, a-H).

1

Properties Purity is evaluated using 1 H NMR spectroscopy. Solid samples of LtBu,iPr2CoCl are brown-purple in color. LtBu,iPr2CoCl is soluble in tetrahydrofuran, CH2Cl2, and toluene, somewhat soluble in diethyl ether, and poorly soluble in pentane. The compound is extremely sensitive to moisture and air. LtBu,iPr2CoCl has been used as a precursor to a three-coordinate cobalt(II) methyl complex.1 * In more recent work after submission and independent checking, we have seen that some batches of CoCl2(THF)1.5 give incomplete conversion to LtBu,iPrCoCl (evident from significant amounts of light blue material in the crude product). If this is a problem, a variant can be used as follows. A mixture of CoCl2 (749 mg, 5.77 mmol, Strem) and THF (200 mL) is heated to reflux overnight under N2 to give a blue solution, and concentrated to 100 mL under vacuum. A pale yellow solution of LtBu,iPrLi(THF) (2.90 g, 5.71 mmol) in THF (70 mL) is added, and the green mixture is heated at 70  C for 4 h. The olivegreen mixture is stirred overnight at room temperature. Volatile materials are removed under reduced pressure, giving a brown residue consisting primarily of LtBu,iPr2Co(m-Cl)2Li(THF)2. Toluene (125 mL) is added, and the mixture is heated at 100  C overnight (this step dissociates THF and precipitates the LiCl). After cooling to room temperature, volatile materials are again removed to give a dark purple residue. The solid is dried under dynamic vacuum at 100  C for 3 hours to remove all traces of THF. The resulting solid is extracted with toluene (150 mL), and the mixture is filtered through a pad of Celite to remove a gray solid. Volatile materials are removed from the purple filtrate to give a semi-crystalline purple solid. This solid is washed with cold pentane (60 mL, precooled to 40  C) and collected to give 1.898 g (55.8% yield) of LtBu,iPrCoCl as a fine purple powder.

12. b-Diketiminate-Supported Nickel(II) and Nickel(I)

45

Acknowledgments This work was supported by the National Science Foundation (CHE-0112658) and the Alfred P. Sloan Foundation (Research Fellowship). References 1. P. L. Holland, T. R. Cundari, L. L. Perez, N. A. Eckert, and R. J. Lachicotte, J. Am. Chem. Soc. 124, 14416 (2002). 2. R. J. Kern, J. Inorg. Nucl. Chem. 24, 1105 (1962).

12. b-DIKETIMINATE-SUPPORTED NICKEL(II) AND NICKEL(I) COMPLEXES OF LME,ME3 (LME,ME3¼2,4-BIS(MESITYLIMIDO)PENTYL) Submitted by MARIE M. MELZER, ELZBIETA KOGUT, MATTHEW S. VARONKA, STEFAN WIESE, and TIMOTHY H. WARREN Checked by SARA S. ROCKS† and PATRICK L. HOLLAND†

General Procedures All experiments were carried out in a dry nitrogen atmosphere using a glovebox and/or standard Schlenk techniques. Diethyl ether and tetrahydrofuran (THF) were first sparged with nitrogen and then dried by passing through activated alumina columns.1 Pentane was first washed with concentrated HNO3/H2SO4 to remove olefins, stored over CaCl2, sparged with nitrogen, and then dried by passing through activated alumina columns.1 Dry toluene was stored over activated 4 A molecular sieves. Deuterated solvents were sparged with nitrogen, dried over  activated 4 A molecular sieves, and stored under nitrogen. Thallous acetate and 2,4-lutidine were purchased from Acros. Anhydrous nickel(II) iodide was purchased from Strem. These reagents were used as received. A. LMe,Me3NiI(2,4-LUTIDINE) TlLMe;Me3 þ NiI2 þ 2; 4-Me2 C5 H3 N ! LMe;Me3 NiIð2; 4-Me2 C5 H3 NÞ þ TlI

*

Department of Chemistry, Georgetown University, Washington, DC 20057-1227. Department of Chemistry, University of Rochester, Rochester, NY 14627.

†

46

Complexes of Bulky b-Diketiminate Ligands

Procedure This synthesis is based on a reported procedure.2 A sample of TlLMe,Me3 (3.00 g, 5.58 mmol) in 100 mLTHF is added to a stirring solution of anhydrous NiI2 (1.74 g, 5.58 mmol) in 60 mL THF containing 3 equiv of 2,4-lutidine (1.95 mL, 16.74 mmol), and the resulting heterogeneous solution retains the dark green/black color of the NiI2. The slurry is stirred overnight. The yellow precipitate of TlI is removed by filtering through Celite, and the filtrate is concentrated to 50 mL and cooled at 35 C overnight. The mother liquor is removed, and the residue is washed with a few milliliters of cold pentane to yield 1.922 g of green/black crystals. The volume of the mother liquor is reduced to 15 mL and cooled again to yield a second  crop of crystals (0.698 g) with a combined yield of 75%. The crystals can be crushed into a fine powder and dried in vacuo to give a THF-free sample. Anal. Calcd. for C30H38N3INi: C, 57.55; H, 6.07; N, 6.71. Found: C, 57.82; H, 6.04; N, 6.65. 1 H NMR (C6D6, 400 MHz, 25 C): d 93.5 (s, 1, 2,4-lut-ArH), 47.5 (s, 6, Arp-Me), 34.8 (s, 12, Ar-o-Me2), 32.7 (s, 4, m-Ar-H), 4.2 (br s, 3, 2,4-lut-Me), 11.3 (br s, 3, 2,4-lut-Me), 46.6 (s, 6, backbone-Me), 118.1 (s, 1, 2,4-lut-ArH). The backbone-H and one 2,4-lut-ArH cannot be observed in the 1 H NMR spectrum. meff ¼ 2.38 B.M. (C6D6 solution). UV–vis (CH2Cl2 (M 1 cm 1)): 527 (562) and 676 (507) nm. Properties LMe,Me3NiI(2,4-lutidine) is very soluble in CH2Cl2 and THF, soluble in toluene, and much less soluble in pentane or diethyl ether. In the absence of a neutral donor ligand, b-diketiminato(II) nickel halide species have a strong tendency to dimerize through bridging halogen groups. For instance, the tetrahedral bridged dimers (LMe,Me2Ni)2 (m-Cl)23 and (LMe,iPr2Ni)2(m-Cl)24 have been structurally characterized. Related Compounds b-Diketiminato monohalide-lutidine species have been used in the synthesis of monoalkyl complexes with Grignard reagents to give [(b-diketiminate)Ni(R)(2,4lutidine)] (R ¼ CH2CH3 and CH2CH2CH3).3 These square planar alkyl complexes dissociate 2,4-lutidine to give the crystallographically characterized b-agostic complexes with the formula LMe,Me2NiR, which are models for intermediates in Ni-catalyzed polymerization of alkenes.5 B. LMe,Me3Ni(2,4-LUTIDINE) TlLMe;Me3 þ NiI2 þ 2; 4-Me2 C5 H3 N ! LMe;Me3 NiIð2; 4-Me2 C5 H3 NÞ þ TlI LMe;Me3 NiIð2; 4-Me2 C5 H3 NÞ þ Na ! LMe;Me3 Nið2; 4-Me2 C5 H3 NÞ þ NaI

12. b-Diketiminate-Supported Nickel(II) and Nickel(I)

47

Procedure This one-pot procedure is based on a published synthesis that employed NiCl2.6 A solution of TlLMe,Me3 (2.50 g, 4.65 mmol) in 20 mLTHF is added to a suspension of NiI2 (1.46 g, 4.65 mmol) and 2,4-lutidine (0.50 g, 4.65 mmol) in ca. 20 mL THF. The reaction is stirred at room temperature overnight and then filtered through Celite to yield a dark green solution.* A 0.5% w/w Na/Hg amalgam (21.4 g of amalgam ¼ 0.107 g Na, 4.65 mmol Na) is added to the solution and stirred vigorously for 3 h. The resulting red solution is decanted away from the remaining amalgam and filtered through Celite. The volatiles are removed over 3 h in vacuo and the red solid is taken up in 40 mL of Et2O. The solution is again filtered through Celite to remove any remaining NaI and then concentrated in vacuo to a volume of about 10 mL. The solution is cooled to 35 C overnight to give deep red crystals. A second crop of crystals is isolated to yield a total of 1.29 g (57%) of product after drying. UV–vis (Et2O with added lutidine, nm (M 1 cm 1)): 396 (5200) and 488 (3300). meff ¼ 2.00 B.M. (C6D6 with ca. 10 equiv added 2,4-lutidine). EPR (toluene with ca. 10 equiv added lutidine, 77K, frozen glass): g ¼ 2.437, 2.131, 2.068.

Properties LMe,Me3Ni(2,4-lutidine) is very soluble in aliphatic and aromatic hydrocarbons as well as diethyl ether and THF. 2,4-Lutidine is added during the characterization owing to the lability of this ligand. The nickel(I) compound is extremely reactive toward halogenated solvents as well as oxygen and water. For instance, blue-green LMe,Me3NiCl(2,4-lutidine) forms upon exposure to CH2Cl2 and a green hydroxo species (LNi)2(m-OH)2 forms upon exposure to dioxygen.7

Related Compounds Nickel(I) b-diketiminates LNi(2,4-lutidine) react with nitric oxide to give stable three-coordinate nitrosyls LNi(NO) (L ¼ LMe,Me2 and LMe,Me3).8 Depending on their steric bulk, these b-diketiminate complexes react with CO to give either dimeric (LMe,Me3Ni)2(m-CO)26 or T-shaped three-coordinate LMe,iPr2Ni (CO)9 derivatives. Addition of adamantyl azide (N3Ad) to LNi(2,4-lutidine) gives the dinickel nitrene (LMe,Me2Ni)2(m-NAd) as well as the terminal LMe,Me3t Ni¼NAd, which undergoes nitrene group transfer to nucleophiles such as CNBu .6 Me,iPr2 10 A related b-diketiminato nickel(I) complex (L Ni)2(m-toluene) also reacts

*

The checkers filtered their product through Celite twice to remove TlI.

48

Complexes of Bulky b-Diketiminate Ligands

with organoazides to give reactive nickel nitrene intermediates11 as well as allows for the isolation of a nickel(II) superoxo complex LMe,iPr2Ni(h2-O2).12 Acknowledgments The authors thank Georgetown University, the Petroleum Research Fund (PRF-G and PRF-AC awards to T.H.W.), and the U.S. National Science Foundation (CHE-0716304 and CHE-0135057, CAREER Award to T.H.W.) for support of this research. References 1. A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen, and F. J. Timmers, Organometallics 15, 1518 (1996). 2. M. M. Melzer, S. Jarchow-Choy, E. Kogut, and T. H. Warren, Inorg. Chem. 47, 10187 (2008). 3. H. L. Wiencko, E. Kogut, and T. H. Warren, Inorg. Chim. Acta 345, 199 (2003). 4. N. A. Eckert, E. M. Bones, R. J. Lachicotte, and P. L. Holland, Inorg. Chem. 42, 1720 (2003). 5. E. Kogut, A. Zeller, T. H. Warren, and T. Strassner, J. Am. Chem. Soc. 126, 11984 (2004). 6. E. Kogut, H. L. Wiencko, L. Zhang, D. E. Cordeau, and T. H. Warren, J. Am. Chem. Soc. 127, 11248 (2005). 7. Y. Li, L. Jiang, L. Wang, H. Gao, F. Zhu, and Q. Wu, Appl. Organomet. Chem. 20, 181 (2006). 8. S. C. Puiu and T. H. Warren, Organometallics 22, 3974 (2003). 9. N. A. Eckert, A. Dinescu, T. R. Cundari, and P. L. Holland, Inorg. Chem. 44, 7702 (2005). 10. G. Bai, P. Wei and D. W. Stephan, Organometallics 24, 5901 (2005). 11. G. Bai and D. W. Stephan, Angew. Chem., Int. Ed. 46, 1856 (2007). 12. S. Yao, E. Bill, C. Milsmann, K. Wieghardt, and M. Driess, Angew. Chem., Int. Ed. 47, 7110 (2008).

13. NICKEL 2,4-BIS-(2,6-DIISOPROPYLPHENYLIMIDO) PENTYL CHLORIDE DIMER, [LMe,iPr2Ni(m-Cl)]2 Submitted by THOMAS R. DUGAN and PATRICK L. HOLLAND Checked by STEFAN WIESE† and TIMOTHY H. WARREN†

General Procedures All manipulations were performed under a nitrogen atmosphere by standard Schlenk techniques or in a glovebox maintained at or below 1 ppm of O2 and H2O. Glassware was dried at 150  C overnight. NMR spectra are referenced to residual CDHCl2 at 5.31 ppm. UV–vis spectra were measured using screw-cap *

Department of Chemistry, University of Rochester, Rochester, NY 14627. Department of Chemistry, Georgetown University, Washington, DC 20057-1227.

†

13. Nickel 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl Chloride Dimer

49

cuvettes. Pentane, diethyl ether, and toluene were purified by passing through activated alumina and Q-5 columns from Glass Contour Co. Deuterated dichloromethane was first dried over CaH2, and then vacuum transferred into a storage container. Celite was dried overnight at 200 C under vacuum. NiCl2(THF)x is prepared by refluxing anhydrous NiCl2 (Strem),*,1 in dry tetrahydrofuran under nitrogen for 24 h.2 The amount of THF coordinated to Ni varies from 0.1 to 0.7, and the stoichiometry of this starting material is obtained through the gravimetric determination of Ni2 þ content with dimethylglyoxime.3 ½LMe;iPr2 LiŠx þ NiCl2 ðTHFÞ0:4 ! LMe;iPr2 Niðm-ClÞ2 NiLMe;iPr2 þ LiCl

Procedure Tan NiCl2(THF)0.4 (335 mg, 2.11 mmol) and [LMe,iPr2Li]x (888 mg, 2.09 mmol) are placed in a 100-mL resealable flask (see Fig. 1 in Section 9), and toluene (30 mL) is added to produce a tan colored slurry. The flask is closed, and the reaction mixture is heated and stirred at 100 C. After 24 h, the dark blue reaction mixture is cooled to room temperature, and the solvent is removed under reduced pressure. Under a nitrogen atmosphere, CH2Cl2 (30 mL) is added to the residue, and the mixture is filtered through 3 cm of Celite. The dark blue solution is concentrated to 18 mL and cooled to 45 C, which yields the first crop of blue crystals (254 mg). A second crop of crystals (228 mg) is obtained by reducing the volume of the supernatant to 6 mL and cooling to 45 C. The solids are washed with pentane to remove traces of LMe,iPr2H and LiLMe,iPr2. Combined yield: 482 mg (45%).† 1

H NMR (CD2Cl2, 500 MHz, 25 C): d 58 (4H, CH(CH3)2 or m-Ar), 36 (4H, CH (CH3)2 or m-Ar), 9.7 (12H, CH(CH3)2), 8.5 (12H, CH(CH3)2), 27 (2H, p-Ar), 90 (6H, CH3), 282 (1H, backbone-H). UV–vis (CH2Cl2, e in M 1 cm 1): 575 (680), 765 (2800) nm. UV–vis (toluene, e in M 1 cm 1): 580 (1200), 740 (2800) nm. Properties Solid samples of [LMe,iPr2NiCl]2 are dark blue, and the purity can be tested by H NMR spectroscopy in CD2Cl2. [LMe,iPr2NiCl]2 is very soluble in CH2Cl2,

1 *

Although commercial material was used here without special precautions, it is uncertain that commercial ‘‘anhydrous’’ NiCl2 is completely free of water. Methods have been reported for removing trace moisture from NiCl2 using anhydrous HCl: see Ref. 1. † The checkers observed a dark green solution after heating, and the green CH2Cl2 solution yielded blue crystals in a yield of 40%. These crystals had spectroscopic properties identical to those described above. The reaction failed with some sources of nickel(II) chloride.

50

Complexes of Bulky b-Diketiminate Ligands

soluble in toluene, and slightly soluble in pentane and diethyl ether. It reacts with tetrahydrofuran to give a purple solution of the adduct LMe,iPr2Ni(Cl)(THF), with UV–vis (THF, e in M 1 cm 1): 520 (1300), 670 (830) nm.2 Related Compounds [LMe,iPr2NiCl]2 has been used as a precursor to a nickel(II) amido complex, and to an unusual T-shaped nickel(I)-carbonyl complex.4 The analogous bromide complex has been used as an ethylene polymerization catalyst,5 and as a source of nickel(I) for group-transfer and bond activation reactions (described in more detail in Section 12). Acknowledgments This work was supported by the National Science Foundation (CHE-0112658) and the Alfred P. Sloan Foundation (Research Fellowship). References 1. (a) D. I. Ryabchikov and V. M. Shul’man, Zh. Prikl. Khim. 7, 1162 (1934). (b) M. Nehme and S. J. Teichner, Bull. Soc. Chim. Fr. 2, 389 (1960). (c) L. E. Topol and S. J. Yosim, Synth. Inorg. Met.-Org. Chem. 3, 47 (1973). 2. N. A. Eckert, E. M. Bones, R. J. Lachicotte, and P. L. Holland, Inorg. Chem. 42, 1720 (2003). 3. A. I. Vogel, Textbook of Quantitative Inorganic Chemistry, 3rd ed., Wiley, New York, 1961, pp. 479–481. 4. N. A. Eckert, A. Dinescu, T. R. Cundari, and P. L. Holland, Inorg. Chem. 44, 7702 (2005). 5. J. Zhang, Z. Ke, F. Bao, J. Long, H. Gao, F. Zhu, and Q. Wu, J. Mol. Catal. A 249, 31 (2006).

14. BIS[COPPER 2,4-BIS-(2,4,6-TRIMETHYLPHENYLIMIDO) PENTYL] TOLUENE, (LMe,Me3Cu)2(m-h2:h2-C7H8) Submitted by YOSRA M. BADIEI and TIMOTHY H. WARREN Checked by KAREN P. CHIANG† and PATRICK L. HOLLAND†

Following Sadighi’s use of copper(I) tert-butoxide in the synthesis of a fluorinated b-diketiminato copper(I) complex,1 a two-step procedure is employed beginning *

Department of Chemistry, Georgetown University, Washington, DC 20057-1227. Department of Chemistry, University of Rochester, Rochester, NY 14627.

†

14. Bis[Copper 2,4-Bis-(2,4,6-Trimethylphenylimido)Pentyl] Toluene

51

with a recently reported preparation for copper(I) tert-butoxide,2 which is then combined with HLMe,Me3 to give [LMe,Me3Cu]2(m-benzene).3 Copper(I) tertbutoxide is first prepared by a modification of the original procedure, which employed LiOBut and anhydrous CuCl. This preparation gave the tetrameric [CuO-tert-Bu]4 when crystallized from hexane or benzene.4 Additionally, an octameric structure [CuO-tert-Bu]8 has been observed in the reaction of mesitylcopper(I) with tert-butanol after crystallization from toluene.5 General Procedures Experiments were carried out in a dry nitrogen atmosphere using a glovebox and/or standard Schlenk techniques. Diethyl ether and tetrahydrofuran (THF) were first sparged with nitrogen and then dried by passing through activated alumina columns.6 Pentane was first washed with conc. HNO3/H2SO4 to remove olefins, stored over CaCl2, sparged with nitrogen, and then dried by passing through 6 activated alumina columns. Dry toluene was purchased from Aldrich and was  stored over activated 4 A molecular sieves. All deuterated solvents were sparged  with nitrogen, dried over activated 4 A molecular sieves, and stored under nitrogen. Potassium tert-butoxide was purchased from Acros. Anhydrous copper(I) iodide was purchased from Strem.

A. COPPER tert-BUTOXIDE KO-tert-Bu þ CuI ! CuO-tert-Bu þ KI Procedure A chilled ( 35 C) solution of commercial potassium tert-butoxide (1.95 g, 17.4 mmol) in 20 mL THF is added to a suspension of anhydrous copper(I) iodide (3.00 g, 15.79 mmol) in 25 mL of THF. The mixture is stirred overnight at room temperature. The resulting solution is then filtered through Celite to remove the precipitated KI followed by removal of all volatiles from the filtrate in vacuo to give a brown-yellow residue. Addition of ca. 5 mL of cold pentane allows the isolation of a pale yellow solid from this residue by filtration and dried in vacuo to afford 1.69 g (78%) of pale yellow copper(I) tert-butoxide. H NMR (benzene-d6): d 1.31 (s, tBu). (CH3), 35.8 (CH3).

1

13

C{1 H} NMR (benzene d6): d 72.6 C

52

Complexes of Bulky b-Diketiminate Ligands

B. BIS[COPPER 2,4-BIS-(2,4,6-TRIMETHYLPHENYLIMIDO) PENTYL] TOLUENE 2 CuO-tert-Bu þ 2 HLMe;Me3 þ C6 H5 Me ! ½LMe;Me3 CuŠ2 ðC6 H5 MeÞ þ 2 tert-BuOH Procedure To a stirring solution of copper(I) tert-butoxide (1.250 g, 9.150 mmol) in 20 mL toluene is added a solution of HLMe,Me3 (2.550 g, 7.620 mmol) in 20 mL of toluene. After stirring for 3 h, the dark brown solution is filtered through Celite, and the volatile materials are removed in vacuo to give a yellow brown, slightly oily residue. This residue is triturated with a small amount of pentane to reveal a yellow solid, which is then recrystallized by extraction into pentane (ca. 5–10 mL) containing a small amount of toluene (1–2 mL) followed by chilling to 35 C. Filtration affords 2.85 g (85%) of the dinuclear product as a yellow solid in two crops. 1

H NMR (benzene-d6): major species: d 6.92 (br s, 4, Ar-H), 4.79 (s, 1, backboneCH), 2.27 (s, 6, Ar-p-CH3), 2.03 (s, 12, Ar-p-CH3), 1.67 (s, 6, backbone-CH3). 13 C{1 H} NMR (benzene d6): 162.7, 148.3, 131.8, 130.3, 128.9, 94.5 (backboneCH), 23.2, 21.1, 18.8, 18.7. Minor species: d 6.81 (s, 8, Ar-H), 4.76 (s, 2, backbone C-H), 2.24 (s, 12, Ar-p-CH3), 1.89 (s, 24, Ar-o-CH3), 1.58 (s, 12, backbone-CH3).

Properties The b-diketiminato copper(I) complex is a pale yellow solid that is freely soluble in benzene, toluene, chlorobenzene, THF, and acetonitrile while partially soluble in diethyl ether and pentane. In solution, the toluene ligand dissociates. When dissolved in benzene, for example, the NMR spectrum exhibits signals for both LMe,Me3Cu(benzene) (major species) and [LMe,Me3Cu]2(benzene) (minor species). The copper(I) complex reacts slowly with chloroform and dichloromethane, resulting in a gradual darkening of the solution to purple. Related Compounds Reaction with oxygen leads to formation of brown (LMe,Me3Cu)2(m-OH)2, presumably through the intermediacy of a dicopper(III) bis(m-oxo) species (LMe,Me3Cu)2(m-O)2.7–9 More hindered b-diketiminato copper(I) complexes such as LtBu,iPr2Cu(MeCN) react with dioxygen to give the crystallographically characterized Cu(III) side-on peroxo complex LtBu,iPr2Cu(h2-O2).10 Employing the diazoalkane N¼N¼CPh2, [(LMe,Me3)Cu]2(m-benzene) may be used for the

14. Bis[Copper 2,4-Bis-(2,4,6-Trimethylphenylimido)Pentyl] Toluene

53

synthesis of dicopper and terminal carbenes [(LMe,Me3)Cu]2(m-CPh2)2 and (LMe, Me3 )Cu¼CPh2.11 Similarly, this copper(I) complex reacts with the organoazide N¼N¼NAr (Ar ¼ 3,5-Me2C6H3) to give the discrete dicopper nitrene [(LMe,Me3) Cu]2(m-NAr), which undergoes nitrene group transfer to nucleophiles such as CNBut.12 Related Cu(I) b-diketiminates have been used for catalytic nitrene group transfer to alkenes with PhI¼NTs to afford aziridines.13 Moreover, the related [(LMe,Cl2)Cu]2(m-benzene) may be prepared similarly from HLMe,Cl2 and copper(I) tert-butoxide and serves as an active C-H amination catalyst with N3Ad, formally inserting the NAd moiety into C-H bonds.2 H NMR spectra in benzene-d6 indicate a mixture of dinuclear {LMe,Me3Cu}2(mbenzene) and mononuclear LMe,Me3Cu(benzene) along with free toluene (d 7.13–7.02 (m, 5, toluene-Ar), 2.10 (s, 3, toluene-CH3)).2Keq ¼ [{LMe,Me3Cu} (benzene)]2/[{LMe,Me3Cu}2(m-benzene)] was about 0.5 M at 25 C with the mononuclear species predominating under typical NMR concentrations (0.01–0.1 M).

1

Acknowledgments The authors thank Georgetown University, the Petroleum Research Fund (PRF-G and PRF-AC awards to T.H.W.), and the U.S. National Science Foundation (CHE-0716304 and CHE-0135057, CAREER Award to T.H.W.) for support of this research. References 1. D. S. Laitar, C. J. N. Mathison, W. M. Davis, and J. P. Sadighi, Inorg. Chem. 42, 7354 (2003). 2. Y. M. Badiei, A. Dinescu, X. Dai, R. M. Palomino, F. W. Heinemann, T. R. Cundari, and T. H. Warren, Angew. Chem., Int. Ed. 47, 9961 (2008). 3. Y. M. Badiei and T. H. Warren, J. Organomet. Chem. 690, 5989 (2005). 4. T. Greiser and E. Weiss, Chem. Ber. 109, 3142 (1976). 5. M. Ha˚kansson, C. Lopes, and S. Jagner, Inorg. Chim. Acta 304, 178 (2000). 6. A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen, and F. J. Timmers, Organometallics 15, 1518 (1996). 7. X. Dai and T. H. Warren, Chem. Commun. 1998 (2001). 8. D. J. E. Spencer, N. W. Aboelella, A. M. Reynolds, P. L. Holland, and W. B. Tolman, J. Am. Chem. Soc. 124, 2108 (2002). 9. D. J. E. Spencer, A. M. Reynolds, P. L. Holland, B. A. Jazdzewski, C. Duboc-Toia, L. Le Pape, S. Yokota, Y. Tachi, S. Itoh, and W. B. Tolman, Inorg. Chem. 41, 6307 (2002). 10. N. W. Aboelella, E. A. Lewis, A. M. Reynolds, W. W. Brennessel, C. J. Cramer, and W. B. Tolman, J. Am. Chem. Soc. 124, 10660 (2002). 11. X. Dai and T. H. Warren, J. Am. Chem. Soc. 126, 10085 (2004). 12. Y. M. Badiei, A. Krishnaswamy, M. M. Melzer, and T. H. Warren, J. Am. Chem. Soc. 128, 15056 (2006). 13. L. D. Amisial, X. Dai, R. A. Kinney, A. Krishnaswamy, and T. H. Warren, Inorg. Chem. 43, 6537 (2004).

54

Complexes of Bulky b-Diketiminate Ligands

15. COPPER 2,4-BIS-(2,6-DIISOPROPYLPHENYLIMIDO) PENTYL CHLORIDE (LMe,iPr2CuCl) Submitted by PATRICK L. HOLLAND Checked by MARIE M. MELZER† and TIMOTHY H. WARREN†

This compound was the first example of a three-coordinate complex of copper(II) outside a protein environment, and it is a precursor to other three-coordinate copper(II) complexes.1 The chloride ligand in this complex has been substituted with thiolate and phenolate ligands to give mimics of type 1 copper sites1,2 and of reduced galactose oxidase,3 respectively. Itoh and Tolman have examined the influence of diketiminate substitution pattern on the copper(II) chemistry.4 General Procedures All manipulations were performed under a nitrogen atmosphere by standard Schlenk techniques or in a glovebox maintained at or below 1 ppm of O2 and H2O. Glassware was dried at 150 C overnight. UV–vis spectra were measured using screw-cap cuvettes. Pentane and dichloromethane were purified by passing through activated alumina and Q-5 columns. Celite was dried overnight at 200 C under vacuum. Anhydrous CuCl2 was purchased from Aldrich and converted to the THF adduct by the method of Kern.5 LMe;iPr2 Li þ CuCl2 ðTHFÞ0:8 ! LMe;iPr2 CuCl þ LiCl

Procedure Orange CuCl2(THF)0.8 (158 mg, 0.822 mmol) is added to a scintillation vial containing a pale yellow solution of [LMe,iPr2Li]x (see Section 3, 351 mg, 0.827 mmol) in tetrahydrofuran (7 mL), causing an immediate color change to red-brown.z After stirring the reaction solution for 1.5 h, the solvent is evaporated under reduced pressure. The residue is extracted with CH2Cl2 (15 mL), and the mixture is filtered through 1 cm of Celite. The volume of the filtrate is reduced to 5 mL, and 2 mL of pentane is added before cooling to 40 C to give one crop of

*

Department of Chemistry, University of Rochester, Rochester, NY 14627. Department of Chemistry, Georgetown University, Washington, DC 20057-1227. z When the checkers added LiLMe,iPr2 to a solution of CuCl2(THF)0.8, it turned dark green. †

15. Copper 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl Chloride

55

crystals (101 mg). Adding 7 mL of pentane to the filtrate and cooling yields a second crop of solid (155 mg), and reducing the volume of supernatant to 3 mL and cooling yields a third crop of solid (96 mg). The solids are washed with pentane to remove traces of LMe,iPr2H and LMe,iPr2Li. The combined yield is 352 mg (82.9%). The purity is verified by UV–vis spectroscopy. UV–vis (0.3–0.4 mM solutions in CH2Cl2, e in M (650).

1

cm 1): 507 (4100), 835 nm

Properties Solid samples of LMe,iPr2CuCl are purple-brown in color. It can also be characterized by its EPR spectrum at 77 K (g|| 2.20, A|| 130  10 4 cm 1, g? 2.05, A? 8  10 4 cm 1). LMe,iPrCuCl is highly soluble in CH2Cl2 and tetrahydrofuran, somewhat soluble in toluene, poorly soluble in MeCN, and insoluble in diethyl ether and pentane. Acknowledgments The author gratefully acknowledges the support of William Tolman and the National Institutes of Health (F32 GM018991) during the time when this synthesis was developed. References 1. P. L. Holland and W. B. Tolman, J. Am. Chem. Soc. 121, 7270 (1999). 2. (a) P. L. Holland and W. B. Tolman, J. Am. Chem. Soc. 122, 6331 (2000). (b) D. W. Randall, S. D. George, P. L. Holland, B. Hedman, K. O. Hodgson, W. B. Tolman, and E. I. Solomon, J. Am. Chem. Soc. 122, 11632 (2000). (c) A. Chowdhury, L. A. Peteanu, P. L. Holland, and W. B. Tolman, J. Phys. Chem. B 106, 3007 (2002). (d) W. Z. Lee and W. B. Tolman, Inorg. Chem. 41, 5656 (2002). 3. (a) B. A. Jazdzewski, P. L. Holland, M. Pink, V. G. YoungJr., D. J. E. Spencer, and W. B. Tolman, Inorg. Chem. 40, 6097 (2001). (b) B. A. Jazdzewski, A. M. Reynolds, P. L. Holland, V. G. Young, S. Kaderli, A. D. Zuberb€uhler, and W. B. Tolman, J. Biol. Inorg. Chem. 8, 381 (2003). 4. (a) C. Shimokawa, S. Yokota, Y. Tachi, N. Nishiwaki, M. Ariga, and S. Itoh, Inorg. Chem. 42, 8395 (2003). (b) D. J. E. Spencer, A. M. Reynolds, P. L. Holland, B. A. Jazdzewski, C. Duboc-Toia, L. Le Pape, S. Yokota, Y. Tachi, S. Itoh, and W. B. Tolman, Inorg. Chem. 41, 6307 (2002). 5. R. J. Kern, J. Inorg. Nucl. Chem. 24, 1105 (1962).

Chapter Two

BORON CLUSTER COMPOUNDS 16. SALTS OF DODECAMETHYLCARBA-closoDODECABORATE( ) ANION, CB11Me12 , AND THE RADICAL DODECAMETHYLCARBA-closo. DODECABORANYL, CB11Me12 Submitted by JOSHUA R. CLAYTON,* BENJAMIN T. KING,* ILYA ZHAROV,* MATTHEW G. FETE,* VICTORIA VOLKIS,* ´ SˇEK,† and JOSEF MICHL*† CHRISTOS DOUVRIS,* MICHAL VALA Checked by KARL MATOSz

The chemistry of the deltahedral carba-closo-dodecaborate( ) anion1 (CB11H12 ) has been reviewed.2,3 It has a highly dispersed charge and no exposed lone pairs, aromatic rings, or multiple bonds, but the boron hydrogens have a distinctly hydridic character and can serve as ligands. Its halogenated derivatives are among the most weakly nucleophilic anions known,4 as is the explosive pertrifluoromethylated analogue.5 The permethylated CB11Me12 is also only weakly nucleophilic,6 and its salts are remarkably lipophilic.7 Solutions of the lithium salt in nonpolar solvents have high Lewis acidity. They catalyze pericyclic reactions,8 and, in the presence of traces of sulfolane, radical polymerization of alkenes.9–11 . The anion can be oxidized to the stable neutral free radical, CB11Me12 , a *

Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309. Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 16610 Prague 6, Czech Republic. z BASF Corporation, Evans City, PA 16033. †

Inorganic Syntheses, Volume 35, edited by Thomas B. Rauchfuss Copyright Ó 2010 John Wiley & Sons, Inc.

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16. Salts of Dodecamethylcarba-closo-Dodecaborate( ) Anion

57

one-electron oxidant with a redox potential 1.15 V above ferrocene (in acetonitrile and in liquid SO2).12,13 The reported6 synthesis of the dodecamethylcarba-closo-dodecaborate( ) anion (CB11Me12 ) involved the use of the expensive sterically hindered base, 2,6-di-tert-butylpyridine, in the second step. An optimized second step reported here utilizes calcium hydride as the only base. The overall procedure starting with CB11H12 provides a 84% yield of 99% pure Cs[CB11Me12]. Procedures for the conversion of the cesium salt to [Me4N][CB11Me12] and Li[CB11Me12] are also . described. Oxidation of the cesium salt to CB11Me12 is straightforward and proceeds in 76% isolated yield. A. CESIUM 1-METHYLCARBA-closo-DODECABORATE( ), Cs[1-Me-CB11H11] ½Me3 NHŠ½CB11 H12 Š þ 2 n-C4 H9 Li ! Li½LiCB11 H11 Š þ Me3 N þ 2 n-C4 H10 Li½LiCB11 H11 Š þ MeI ! Cs½1-Me-CB11 H11 Š þ LiI Procedure* Commercial† trimethylammonium carba-closo-dodecaborate( ), [Me3NH] [CB11H12], which can also be prepared in the laboratory from decaborane14 or sodium borohydride,15 is methylated on carbon in 94% yield using an improved version of a published16 alkylation procedure. [Me3NH][CB11H12] (7.0 g, 34.5 mmol) is placed in a 300-mL Schlenk flask and dried under vacuum at 100 C for 60 min. The flask is charged with argon and THF (150 mL, freshly distilled from Na/benzophenone) is added. A 1.6 M solution of n-BuLi in hexanes (1 equiv, 21.6 mL, 34.5 mmol) is added dropwise over 1 h at 0 C. The solution is allowed to warm to room temperature and is stirred for an additional 1 h. The volume of the mixture is then reduced slowly to 50 mL by removing the argon flow and connecting the flask to a vacuum line (NMe3 and almost half of the THF are removed). The flask is filled again with argon, charged with an additional 100 mL of fresh THF, and cooled to 78 C using a dry ice/acetone bath. At this temperature, a 1.6 M solution of n-BuLi in hexanes (3 equiv, 64.7 mL, 103.5 mmol) is added dropwise and the mixture is allowed to reach room temperature with stirring. It is then stirred at room temperature for 3 h. Methyl iodide (4 equiv, 8.6 mL, 138 mmol) is added and the mixture is stirred for 3 h. Water (25 mL) is *

If the methylation is performed on Cs[CB11H12]13 instead of the commercial Me3NH[CB11H12], using 1.5 equiv of n-butyllithium and 2 equiv of methyl iodide, it proceeds to completion and a second step is not required. † Katchem, Ltd., El. Krasnohorske 6, 11000 Praha 1, Czech Republic.

58

Boron Cluster Compounds

added and the reaction mixture evaporated to dryness. The residue is extracted with diethyl ether (3  100 mL) and the combined extracts are washed with a 20% solution of CsCl (3  50 mL). The combined CsCl wash is extracted with diethyl ether (3  50 mL). The combined organic phase is evaporated to dryness and the crude solid recrystallized from a minimum amount of water (10–20 mL) with filtration at 70–80 C followed by cooling to room temperature. It provides 9.31 g (94%) of 97% pure Cs[1-Me-CB11H11], containing 3% Cs[CB11H12]. If desired, the material can then be dried and methylated again under the same conditions, and worked up in the same manner to provide at least 99% pure Cs[1-Me-CB11H11], in which Cs[CB11H12] is undetectable by 1 H NMR and ESI-MS. Anal. (for Ph4P[1-Me-CB11H11]) Calcd. for C26B11H34P: C, 62.91; H, 6.90. Found C, 63.20; H, 6.84. NMR spectrum of the Ph4P þ salt in acetone-d6: 1 H{11 B} NMR: d 7.92 [t, 4H, PPh4 þ ], 7.76 [m, 8H, PPh4 þ ], 7.60 [m, 8H, PPh4 þ ], 1.74 [s, 5H], 1.54 [s, 5H], 1.50 [s, 3H, CH3 (1)], 1.46 [s, 1H, H (12)]; 11 B{1 H} NMR: d 11.09 [s, 1B, B(12)], 12.83 [s, 10B, B(2–11)]; 13 C{1 H} NMR: d 135.63 [d, PPh4 þ ], 131.37 [d, PPh4 þ ], 118.82 [d, PPh4 þ ], 27.68 [s, CH3 (1)]. ESI-MS (m/e): 157. IR (Cs þ salt, KBr pellet) 487, 728, 938, 1039, 1194, 1311, 1383, 1458, 2544, 2875, 2938 cm 1. B. CESIUM, TETRAMETHYLAMMONIUM, and LITHIUM DODECAMETHYLCARBA-closo-DODECABORATES( ), Cs[CB11Me12], [NMe4][CB11Me12], and Li[CB11Me12]

2 Cs½1-Me-CB11 H11 Š þ 22 MeOTf þ 11 CaH2 ! 2 Cs½CB11 Me12 Š þ 11 CaðOTfÞ2 þ 22 H2 Procedure & Caution. Methyl triflate is highly toxic. Handle with extreme care in a well ventilated hood. Calcium hydride (8.4 g, 200 mmol) is added to Cs[1-Me-CB11H11] (1.45 g, 5 mmol) dissolved in 19 mL of sulfolane (24 g, 200 mmol) in a 250-mL threenecked round-bottomed flask, and the system is placed under argon. The mixture is stirred. The reaction temperature should be held constant at 25 C to avoid fluctuations in reaction time and formation of by-products (triflyloxy derivatives). To this mixture is added freshly distilled methyl triflate (11.3 mL, 16.4 g, 100 mmol) with a syringe pump over a period of 20 h. Stirring is continued until the reaction mixture solidifies (2–3 days). A solution of 5.5 mL of methyl triflate (8 g, 48.7 mmol) in 10 mL of sulfolane is added to the reaction mixture in one

16. Salts of Dodecamethylcarba-closo-Dodecaborate( ) Anion

59

portion and stirring is continued. After a further 2 days of stirring, the reaction is normally complete, depending on reagent quality. A small aliquot is taken out and checked by ESI-MS. The solidified reaction mixture is diluted with 300 mL of dry methylene chloride and CaH2 is removed by vacuum filtration. The filtrate is neutralized slowly with a few milliliters of 27% ammonium hydroxide solution and the organic phase is evaporated. The remaining solution is extracted with diethyl ether (3  150 mL). Cs[CB11Me12]. The combined organic layer is washed with 20% aqueous CsCl (3  50 mL). The combined CsCl wash is extracted with diethyl ether (3  50 mL). The combined ether solution is evaporated and the residual sulfolane is removed by heating the sample under reduced pressure (190 C (decomp.). 1 H NMR (acetone-d6): d 2.61 (9H, s, 3  NCH3), 4.91 (3H, apparent d, splitting 8.5 Hz, with unresolved fine structure, 3  NCHHN), and 5.06 (3H, apparent d, splitting 8.5 Hz, with unresolved fine structure, 3  NCHHN). 13 C NMR (acetone-d6): d 42.9 (CH3), 83.5 (NCH2N), and 226.0 (CO). IR (KBr): 1895, 1772 (sh), 1740 (CO). Properties W(CO)3(Me3TACH) is a yellow-tan air-sensitive compound. It also forms at lower temperatures by the reaction of Me3TACH with W(CO)3(RCN)3 (R ¼ Me or Et) in THF, and in these cases, the isolated complex is bright yellow. Spectroscopic analysis indicates no appreciable differences between the products prepared by the different methods. Exposure of the solid to air produces a dark brown solid and W(CO)6. Under an inert atmosphere, the complex is stable indefinitely in the solid state. The complex is insoluble in nonpolar solvents and only sparingly soluble in polar solvents (ca. 0.05 mg/mL in acetone). Dissolution of the complex in DMSO rapidly affords the solvolysis product W(CO)3(DMSO)3. The 1 H NMR spectrum can be analyzed as described above for the Cr complex. References 1. A. L€ uttringhaus and W. Kullick, Tetrahedron Lett. (10), 13 (1959). 2. H. Schumann, Z. Naturforsch. B 50, 1038 (1995). 3. N. L. Armanasco, M. V. Baker, M. R. North, B. W. Skelton, and A. H. White, J. Chem. Soc., Dalton Trans. 1145 (1998). 4. N. L. Armanasco, M. V. Baker, M. R. North, B. W. Skelton, and A. H. White, J. Chem. Soc., Dalton Trans. 1363 (1997).

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5. M. V. Baker and M. R. North, J. Organomet. Chem. 565, 225 (1998). 6. M. V. Baker, D. H. Brown, B. W. Skelton, and A. H. White, J. Chem. Soc., Dalton Trans. 763 (2000). 7. M. V. Baker, D. H. Brown, B. W. Skelton, and A. H. White, J. Chem. Soc., Dalton Trans. 1483 (1999). 8. W.-Y. Yeh, S.-M. Peng, and G.-H. Lee, J. Organomet. Chem. 671, 145 (2003). 9. W.-Y. Yeh, C.-S. Lin, S.-M. Peng, and G.-H. Lee, Organometallics 23, 917 (2004). 10. N. Kuhn, M. Go¨hner, and M. Steimann, Z. Naturforsch. 56b, 95 (2001). 11. J. Graymore, J. Chem. Soc. 134, 1490 (1931). 12. K. R. Birdwhistell, Inorg. Synth. 29, 141 (1992). 13. A. R. Manning, P. Hackett, R. Birdwhistell, and P. Soye, Inorg. Synth. 28, 148 (1990). 14. G. J. Kubas and L. S. Van der Sluys, Inorg. Synth. 28, 29 (1990). 15. C. H. Bushweller, M. Z. Lourandos, and J. A. Brunelle, J. Am. Chem. Soc. 96, 1591 (1974).

28. MANGANESE TRICARBONYL TRANSFER (MTT) AGENTS Submitted by SANG BOK KIM, SIMON LOTZ,† SHOUHENG SUN, YOUNG KEUN CHUNG,z ROBERT D. PIKE,§ and DWIGHT A. SWEIGART Checked by MARIA E. CARROLL,# DIDIER MORVAN,# and THOMAS B. RAUCHFUSS#

The complexes [Mn(h6-arene)(CO)3] þ are isoelectronic with [Cr(h6-arene)(CO)3] and, as is the case with the chromium complexes, can be synthesized with a wide variety of arenes.1 Functionalized arene ligands are of particular importance because [Mn(arene)(CO)3] þ undergoes high-yield regio- and stereoselective attack by a wide range of nucleophiles.2 A number of methods are available to make p-arene tricarbonyl complexes of manganese(I), and the one selected is often determined by the nature of the arene ring to be coordinated, which can have substituents that are electron donating, electron withdrawing, or sterically demanding.3 Condensed polyaromatic hydrocarbons such as naphthalene and heterocyclic fused ring systems such as indole, benzofuran, and benzothiophene can also p-bond in a h6-manner to manganese(I) tricarbonyl. Analogously, the heteroaromatic five-membered thiophene ring can p-bond in a h5-fashion and thereby donate six electrons. *

Department of Chemistry, Brown University, Providence, RI 02912. Department of Chemistry, University of Pretoria, Pretoria 0002, South Africa . z Department of Chemistry, Seoul National University, Seoul 151-742, Korea . § Department of Chemistry, College of William and Mary, Williamsburg, VA 23187. # Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801. †

28. Manganese Tricarbonyl Transfer (MTT) Agents

115

Most methods to prepare [Mn(arene)(CO)3] þ make use of the abstraction of the halogen from [Mn(CO)5X] (X ¼ halogen) by Lewis acids such as AlCl3 (referred to as the Fischer–Hafner method)4 or by precipitation of silver(I) halide (referred to as the silver method).5 The [Mn(CO)5] þ species can also be generated via other indirect methods, most notably using dimanganese decacarbonyl and trifluoroacetic anhydride in acidic medium.6 Coordination of the arene rings is often achieved under harsh thermal conditions by refluxing in appropriate solvents, with concomitant substitution for several carbonyl ligands. The very popular silver method involves using silver(I) salts with weakly coordinating anions such as perchlorate,7 triflate,8 or tetrafluoroborate9 and is the method of choice for arenes with high sensitivity to acid. The silver method uses milder reaction conditions in comparison to the Fischer–Hafner or trifluoroacetic anhydride (TFA) procedures. The advantages and scope of these different methods have been discussed by Pike and coworkers.3 It should be noted that the synthesis of [Mn(arene)(CO)3] þ complexes starting from [Mn(CO)5X] is often problematic when the arene contains electron-withdrawing substituents. However, in recent significant work, it has been shown that access to such electron-deficient systems is possible via the palladium-catalyzed substitution for chloride in (h5-chlorocyclohexadienyl)Mn(CO)3, followed by hydride abstraction.10 A synthetic strategy conceptually different from the ones that start with Mn(CO)5X involves the initial generation of an intermediate arene manganese tricarbonyl complex that has an arene ring sufficiently labile that it can be easily replaced by reaction with a second arene. This method can also be seen as transferring a Mn(CO)3 þ fragment from one arene ligand to another (Eq. 1). Studies of the stability of p-arene manganese tricarbonyl complexes with polycyclic condensed arenes (‘‘polyarenes’’) indicated that these compounds were ideally suited to act as Mn(CO)3 þ transfer reagents (MTT reagents).11 It was observed that the polyarene complexes undergo ring slippage processes much more readily than do the monocyclic analogues, which has been ascribed to a smaller loss in resonance energy that accompanies the h6 ! h4 transformation in the polyarene cases. Facile ring slippage is the requirement for the reaction shown in Eq. 1 to be useful, and a series of [Mn(h6-polyarene)(CO)3] þ complexes have been tested for their ability to effectively transfer the Mn(CO)3 þ fragment in this manner. A key feature of the synthesis of [Mn(arene)(CO)3] þ via MTT reagents is the very mild conditions—simply warming the reactants in dichloromethane solvent (see below). The MTT reagents of choice contain a readily displaceable naphthalene or acenaphthene ligand (Fig. 1). Both have been used with success and both are quite stable thermally as solids or in solution in the absence of nucleophilic reagents. The MTT method for the synthesis of [Mn(arene)(CO)3] þ complexes often translates into an improved yield or a cleaner reaction product in comparison to that afforded by other synthetic methods.11

116

Organometallic Reagents

Figure 1. Mn(h6-polyarene)(CO)3 þ complexes that function as excellent MTT reagents.

½Mnðarene0 ÞðCOÞ3 Š þ þ arene ! ½MnðareneÞðCOÞ3 Š þ þ arene0 ðarene0 ¼ labile arene ligandÞ

ð1Þ

Herein, an example is given of how the MTT method can be used to coordinate Mn(CO)3 þ to a p-molecule. Figure 2 gives examples of such p-systems. Thus, Mn (CO)3 þ can be coordinated to redox-active hydroquinones,12 sterically encumbered aromatics, and the curved (convex) face of centropolyindanes.13 Coordination to metal complexes containing a free arene or thiophene ring affords binuclear systems useful in construction of nonlinear optical materials.14 It has been shown that chiral metallocenes can react with MTT reagents by the transfer of a cyclopentadienyl ring to generate planar chiral (cyclopentadienyl)Mn(CO)3 complexes with high stereoselectivity.15 Alternatively, MTT reagents can transfer the Mn(CO)3 þ unit to metallocenes without Cp ring cleavage, resulting in novel

Figure 2. Examples of molecules that react with MTT reagents by p-coordination of the Mn(CO)3 þ unit.

28. Manganese Tricarbonyl Transfer (MTT) Agents

117

bimetallic multidecker systems capped by the manganese tricarbonyl fragment.15 For each of the representative compounds shown below, the MTT method affords products that can be obtained only in lower yields or cannot be obtained at all by the other synthetic methods for the coordination of Mn(CO)3 þ . A. ACENAPHTHENE(TRICARBONYL)MANGANESE(I)*

MnðCOÞ5 Br þ AgBF4 ! MnðCOÞ5 BF4 þ AgBr MnðCOÞ5 BF4 þ C12 H10 ! ½MnðC12 H10 ÞðCOÞ3 ŠBF4 þ 2 CO Procedure Under an atmosphere of nitrogen, a 250-mL two-necked flask is charged with Mn (CO)5Br16 (1.10 g, 4.0 mmol) along with a Teflon-coated stirring bar. Dichloromethane (50 mL, Fisher HPLC Grade D143-1) is added, and the solution stirred until all the [Mn(CO)5Br] dissolves. The flask is covered with aluminum foil to exclude light, and silver tetrafluoroborate is added (0.82 g, 4.2 mmol). After stirring the solution for 20 min, a solution of acenaphthene (0.93 g, 6.0 mmol) in 10 mL dichloromethane is added. The reaction mixture is refluxed for 3–4 h. After being cooled to room temperature, the reaction mixture is filtered through a Celite plug into a flask containing 250 mL diethyl ether while stirring vigorously. The Celite removes AgBr together with some undissolved product. The residue on the Celite is washed with small portions (3  10 mL) of dichloromethane, which are collected separately, concentrated, and added dropwise to the stirred ether solution. The product separates as a fine yellow solid. The yellow powder is filtered off, washed with diethyl ether, and dried in vacuo. Although normally quite pure at this stage, the solid can be further purified by redissolving in a minimum of dichloromethane and treating as before by adding the solution in a dropwise manner to a stirred solution of diethyl ether (250 mL). Yield: 1.32 g (3.48 mmol, 87%). Anal. Calcd (%): C, 47.37; H, 2.63. IR (CH2Cl2): 2072, 2012 cm 1. Found (%): C, 47.23; H, 2.72. 1 H NMR (CD2Cl2): d 8.07 (m, H6), 7.90–7.75 (m, H5,7), 7.17 (d, J ¼ 7 Hz, H4), 6.75 (m, H3), 6.58 (d, J ¼ 6 Hz, H2), 3.90–3.60 (m, H9,10).

*

Checkers obtained yields about 30% lower than reported probably because of incomplete precipitation of the products from the dichloromethane reaction solution. After the addition of the arene, the reaction of Mn(CO)5Br with AgBF4 was monitored by IR spectroscopy. In some reactions, it was found that additional AgBF4 (up to 20%) was required to completely convert all Mn(CO)5Br.

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Organometallic Reagents

Properties Acenaphthene(tricarbonyl)manganese(I) tetrafluoroborate11 is a light yellow solid (mp 130 C decomp.) and is best kept under inert atmosphere to avoid contact with moisture, with which it reacts to liberate the coordinated acenaphthene. Similarly, it reacts rapidly with nucleophilic solvents such as acetonitrile and DMSO but is highly soluble and stable in CH2Cl2. It is insoluble in ether and aromatic or aliphatic hydrocarbons. The acenaphthene complex [Mn(h6-C12H10)(CO)3]BF4 is the MTT reagent of choice in terms of cost, ease of synthesis, and shelf life. B. NAPHTHALENE(TRICARBONYL)MANGANESE(I) MnðCOÞ5 Br þ AgBF4 ! MnðCOÞ5 BF4 þ AgBr MnðCOÞ5 BF4 þ C10 H8 ! ½MnðC10 H8 ÞðCOÞ3 ŠBF4 þ 2 CO Procedure The complex was prepared from Mn(CO)5Br16 (1.10 g, 4.0 mmol), silver tetrafluoroborate (0.82 g, 4.2 mmol), and naphthalene (0.77 g, 6.0 mmol) by a procedure analogous to that employed for the acenaphthene analogue. The product, a pale yellow solid, was again isolated by filtration, washed with ether, and dried in vacuo. Yield: 1.22 g (3.44 mmol, 86%). Anal. Calcd (%): C, 44.11; H, 2.28. Found (%): C, 43.87; H, 2.30. IR (CH2Cl2): 2077, 2022 cm 1. 1 H NMR (CD2Cl2): d 8.06 (s, H5–8), 7.50–7.35 (m, H1,4), 6.80–6.65 (m, H2,3). Properties Naphthalene(tricarbonyl)manganese(I) tetrafluoroborate11 is a pale yellow solid (mp 108 C decomp.). It is best kept under inert atmosphere due to its moisture sensitivity. It dissolves readily in CH2Cl2 but is insoluble in ether and aromatic or aliphatic hydrocarbons. As a MTT reagent, the naphthalene complex undergoes arene substitution faster than the acenaphthene(tricarbonyl)manganese(I) analogue. C. SYNTHESIS OF h6-N,N-DIMETHYLANILINE (TRICARBONYL)-MANGANESE(I) TETRAFLUOROBORATE, [Mn(h6-C6H5NMe2)(CO)3]BF4 ½MnðC12 H10 ÞðCOÞ3 ŠBF4 þC6 H5 NMe2 !½MnðC6 H5 NMe2 ÞðCOÞ3 ŠF4 þC12 H10

28. Manganese Tricarbonyl Transfer (MTT) Agents

119

Procedure & Caution. The procedure involves heating a dichloromethane solution to 70 C, thus generating up to several atmospheres pressure. For this reason, the experimental apparatus should be placed behind an appropriate protective shield. A 30-mL pressure tube was flame dried under nitrogen and charged with [Mn(h6C12H10)(CO)3]BF4 (0.21 g, 0.55 mmol) and N,N-dimethylaniline (1.40 mL, 1.10 mmol) dissolved in 20 mL dichloromethane. N,N-Dimethylaniline was dried  prior to use with 4 A molecular sieves. The tube was sealed, heated in a silicon oil bath at 75 C for 3 h, and then cooled to room temperature. After evaporation to ca. 5 mL, this solution was added slowly to 100 mL of diethyl ether through a plug of Celite. The light yellow solid was filtered off and washed three times with 10 mL aliquots of diethyl ether. The isolated yield of [Mn(h6-C6H5NMe2)(CO)3]BF4 was 0.18 g (0.52 mmol, 94%). Anal. Calcd (%): C, 38.08; H, 3.20; N, 4.04. Found (%): C, 39.04; H, 3.17; N, 4.30. IR (CH2Cl2): 2066, 2000 cm 1. 1 H NMR (acetone-d6): d 6.92 (t, H3,5), 6.09 (t, H4), 5.87 (d, H2,6), 3.35 (s, Me). Properties N,N-Dimethylaniline(tricarbonyl)manganese(I) tetrafluoroborate is a yellow solid (mp 168 C with decomp.). It dissolves readily in CH2Cl2 but is insoluble in ether, aromatic, and aliphatic hydrocarbons.

References 1. D. A. Sweigart, J. A. Reingold, and S. U. Son, Manganese compounds containing CO ligands, in Comprehensive Organometallic Chemistry, 3rd ed., R. H. Crabtree and D. M. P. Mingos, eds., Elsevier, Oxford, 2006, Vol. 5, Chapter 10, pp. 761–814. 2. (a) L. A. P. Kane-Maguire, E. D. Honig, and D. A. Sweigart, Chem. Rev. 84, 525 (1984). (b) R. D. Pike, D. A. Sweigart, Coord. Chem. Rev. 187, 183 (1999). (c) D. A. Sweigart, T. J. Alavosus, Y. K. Chung, W. A. Halpin, E. D. Honig, and J. C. Williams, Metal carbonyl cations with cyclic p-hydrocarbon ligands, in Organometallic Synthesis, R. B. Kingand J. J. Eisch, eds., Academic Press, New York, 1988, Vol. 4, p. 108. 3. J. D. Jackson, S. J. Villa, D. S. Bacon, R. D. Pike, and G. B. Carpenter, Organometallics 13, 3972 (1994). 4. (a) G. Winkhaus, L. Pratt, and G. Wilkinson, J. Chem. Soc. 3807 (1961). (b) P. L. Pauson and J. A. Segal, J. Chem. Soc., Dalton Trans. 1677 (1975). (c) L. A. P. Kane-Maguire and D. A. Sweigart, Inorg. Chem. 18, 700 (1979). 5. (a) R. Mews, Angew. Chem., Int. Ed. Engl., 14, 640 (1975). (b) F. L. Wimmer, M. R. Snow, and Aust. J. Chem. 31, 267 (1978). (c) R. Uson, V. Riera, J. Gimano, M. Laguna, M. P. Gamasa, J. Chem. Soc., Dalton Trans. 966 (1974). (d) F. A. Cotton, D. J. Darensbourg, and W. S. Kolthammer, Inorg. Chem. 20, 1267 (1981).

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Organometallic Reagents

6. (a) M. I. Rybinskaya, V. S. Kaganovich, and A. R. Kydinov, Izv. Akad. Nauk. SSR Ser. A Khim. 885 (1984). (b) A. J. Pearson and H. Shin, Tetrahedron 48, 7527 (1992). 7. (a) K. K. Basin, W. G. Balkeen, and P. L. Pauson, J. Organomet. Chem. 204, C25 (1981). (b) Y.-A. Lee, Y. K. Chung, Y. Kim, and J. H. Jeong, Organometallics 9, 2851 (1990). (c) E. Jeong and Y. K. Chung, J. Organomet. Chem., 434, 225 (1992). (d) S. S. Lee, J-S. Lee, and Y. K. Chung, Organometallics 12, 4640 (1993). (e) S. C. Chaffee, J. C. Sutton, C. S. Babbitt, J. T. Maeyer, K. A. Guy, and R. D. Pike, Organometallics 17, 5568 (1998). 8. S. P. Schmidt, J. Nitschke, and W. C. Trogler, Inorg. Synth. 26, 113 (1989). 9. W. J. Ryan, P. E. Peterson, Y. Cao, P. G. Willard, D. A. Sweigart, C. D. Baer, C. F. Thompson, Y. K. Chung, and T.-M. Chung, Inorg. Chim. Acta 211, 1 (1993). 10. A. Auffrant, D. Prim, F. Rose-Munch, E. Rose, S. Schouteeten, and J. Vaissermann, Organometallics 22, 1898 (2003). 11. (a) S. Sun, L. K. Yeung, D. A. Sweigart, T.-Y. Lee, Y. K. Chung, S. R. Switzer, and R. D. Pike, Organometallics 14, 2613 (1995). (b) M. Oh, J. A. Reingold, G. B. Carpenter, and D. A. Sweigart, Coord. Chem. Rev. 248, 561 (2004). 12. S. Sun, G. B. Carpenter, and D.A. Sweigart, J. Organomet. Chem. 512, 257 (1996). 13. C. A. Dullaghan, G. B. Carpenter, D. A. Sweigart, D. Kuck, C. Fusco, and R. Curci, Organometallics 19, 2233 (2000). 14. (a) I. S. Lee, H. Seo, and Y. K. Chung, Organometallics 18 1091 (1999). (b) S. S. Lee, T.-Y. Lee, J. E. Lee, I.-S. Lee, Y.K. Chung, and M.S. Lah, Organometallics 15, 3664 (1996). 15. (a) E. J. Watson, K. L. Virkaitis, H. Li, A. J. Nowak, J. S. D’Acchioli, K. Yu, G. B. Carpenter, Y. K. Chung, and D. A. Sweigart, Chem. Commun. 457 (2001). (b) S. U. Son, K. H. Park, S. J. Lee, Y. K. Chung, and D. A. Sweigart, Chem. Commun. 1290 (2001). 16. M. H. Quick and R. J. Angelici, Inorg. Synth. 19, 160 (1979).

29. BIS(1,5-CYCLOOCTADIENE)NICKEL(0) Submitted by J. WOLFRAM WIELANDT and DAVID RUCKERBAUER Checked by T. ZELL§ and U. RADIUS§

Bis(1,5-cyclooctadiene)nickel(0) is useful for the synthesis of a variety of novel nickel complexes1–5 since the 1,5-cyclooctadiene ligands are easily displaced by other stronger electron-donating ligands.6 The compound has been prepared by reduction of nickel(II) salts with manganese powder7 or by sodium8 in the presence of 1,5-cyclooctadiene. Moreover, triethylaluminum has become a common reducing agent, but butadiene is required as the protective atmosphere.9 A butadiene-free preparation procedure has been reported that uses diisobutylaluminum hydride (DIBAH) to reduce technical grade (90%) Ni3(acac)6.10 Here, di(n-butyl)magnesium is used as an alternative,4 since it is cheap and much less dangerous than triethylaluminum. Also, no butadiene atmosphere is required. * §

Institute of Chemistry, Inorganic Department, Karl-Franzens-University, 8010 Graz, Austria. Institut fu¨r Anorganische Chemie der Julius-Maximilians-Universita¨t Wu¨rzburg, Am Hubland, D-97074 Wu¨rzburg, Germany.

29. Bis(1,5-Cyclooctadiene)Nickel(0)

121

Di(n-butyl)magnesium can be purchased as a 1.0 M solution in n-heptane. Alternatively, the preparative method given below can be applied, which follows the general synthetic pathway for dialkyl magnesium compounds outlined by Kamienski.11 The preparation involves the treatment of an ethereal solution of (n-butyl)magnesium bromide with n-butyl lithium solution in hexanes. Other methods of preparation include treatment of (n-butyl)magnesium halide solutions with Me(OCH2CH2)nOMe,12 1,4-dioxane,13 and THF,14 or reaction of magnesium hydride with 1-butene under pressure in an autoclave.15 & Caution. Di(n-butyl)magnesium reacts violently with water, and in the dry state it ignites spontaneously upon exposure to air. Nickel and its compounds are regarded as carcinogens. It also can cause allergic reactions, asthma, and chronic bronchitis. Uptake of large quantities of nickel may lead to lung embolism, respiratory failure, and heart disorders. Therefore, all manipulations should be performed with care in a well-ventilated hood. Materials 1,5-Cyclooctadiene (Aldrich Chemicals) was distilled from sodium and stored under argon. n-Butyl bromide and 1.6 M n-butyl lithium solution were purchased from Aldrich and used as received. Solvents used in the syntheses were dried with appropriate drying agents16 and freshly distilled under inert gas before use. All procedures are performed in an anhydrous, oxygen-free atmosphere using standard techniques for bench-top inert atmosphere reactions.17,18 A. HEXAKIS(ACETYLACETONATO)TRINICKEL(II)

NiðNO3 Þ2 6 H2 Oþ2NaC5 H7 O2 !NiðC5 H8 O2 Þ2 2H2 Oþ4H2 Oþ2NaNO3 3 NiðC5 H8 O2 Þ2 2 H2 O!Ni3 ðC5 H8 O2 Þ6 þ6 H2 O Procedure Under air, Ni(NO3)26H2O (29.8 g, 0.1 mol) and 2,4-pentanedione (20.5 g, 0.205 mol) are dissolved in water (40 mL) and treated with a 0.2 M aqueous solution of NaOH (40 mL). Immediately, a turquoise precipitate is formed. After the addition is complete, the mixture is heated to reflux for 30 min, cooled to ambient temperature, and filtered. The filter cake is washed with water (50 mL) and dried under air for 2 h; yield: 26.9 g (92%) of light turquoise bis(2,4-pentadionato) nickel(II) dihydrate. In a 500-mL round-bottomed flask attached to a Dean–Stark apparatus, a suspension of bis(2,4-pentadionato)nickel(II) dihydrate (26.9 g,

122

Organometallic Reagents

0.092 mol) in toluene (150 mL) is carefully heated to reflux under air. (Note: An oil bath should be applied as heating source, not a heating mantle. The mixture tends to foam, and when heating is performed too rapidly, some of the solid material spills over into the water collector.)9 The mixture is heated under reflux for 48 h until no more water is separated. A dark green slurry is formed, which is allowed to cool to ambient temperature under inert gas. The insoluble parts are removed by filtration with exclusion of air. The filter cake is extracted with dry toluene (20 mL). All filtrates are combined and are taken to dryness under vacuum. The oily residue is rinsed with ether (30 mL) in order to remove traces of grease. Solvent is decanted from the green solid, which is dried under vacuum. Yield: 17.0 g (0.066 mol).

B. DI(n-BUTYL)MAGNESIUM

n-C4 H9 Br þ Mg ! n-C4 H9 MgBr n-C4 H9 MgBr þ n-C4 H9 Li ! ðn-C4 H9 Þ2 Mg þ LiBr Procedure A 500-mL three-necked round-bottomed flask is equipped with a reflux condenser, topped by a gas outlet, and two pressure-equalizing dropping funnels (one with 100 mL volume and the other with 250 mL volume). Before the second dropping funnel is attached, dry magnesium turnings (6.1 g, 0.25 mol) and a few crystals of iodine are added to the flask. The apparatus is flushed with nitrogen for a few minutes, and then the small dropping funnel is charged with n-butyl bromide (34.26 g, 0.25 mol) and the large one is filled with dry diethyl ether (100 mL). The magnesium turnings are heated without solvent with a heating gun until violet fume has filled the whole apparatus. Then, approximately 5% of the volume of n-butyl bromide is added to the hot magnesium turnings, followed by dropwise addition of the solvent. As soon as the Grignard reaction starts, the bromide and the solvent are added in a dropwise manner to keep the mixture refluxing gently. (Note: The bromide should be added cautiously. An efficient reflux condenser is recommended.) Upon complete addition, the dark gray mixture is kept under reflux for another 30 min using a water bath. Into the second reaction apparatus consisting of a 1-L three-necked roundbottomed flask equipped with a reflux condenser, a gas inlet, and a pressureequalizing 250-mL addition funnel, the Grignard solution is transferred under argon via cannula in order to separate it from unreacted magnesium. (Note: By weighing the amount of unreacted Mg, the amount of n-butyl lithium solution required can be accurately determined. Usually, the conversion is 90–95%.) The dropping funnel is now charged with 1.6 M n-butyl lithium solution in hexanes

29. Bis(1,5-Cyclooctadiene)Nickel(0)

123

(138 mL, 0.220 mol) and added dropwise under cooling with an ice bath. The resulting gray suspension is heated at reflux for 30 min, cooled to ambient temperature, and filtered under nitrogen using a Schlenk frit attached to a 1-L Schlenk flask. (Note: It is recommended that the inorganic salts be allowed to settle prior to filtration, and the filtration process itself should be performed without pressure to prevent LiBr from passing through the filter.) The nearly colorless clear filtrate is collected and used in the next step. (Note: An excess of reducing agent does not affect the preparation described in step B.) To isolate the dibutyl magnesium, the filtrate is evaporated to dryness under vacuum and the resulting white solid is further dried at 10 2 mbar at 60 C for 15 h to give 33.1 g (95%). This solid contains small amounts of lithium bromide.

C. BIS(1,5-CYCLOOCTADIENE)NICKEL(0) Ni3 ðC5 H7 O2 Þ6 þ 6 ðn-C4 H9 Þ2 Mg þ 6 C8 H12 ! 3 ðC8 H12 Þ2 Ni þ 6 ðn-C4 H9 ÞMgðC5 H7 O2 Þ þ 3 C8 H18 Procedure A 1-L three-necked round-bottomed flask is equipped with a 100-mL pressureequalizing dropping funnel and two gas outlets, one attached to a gas bubbler and the other to an inert gas source. The flask is charged with Ni3(C5H7O2)6 (9.79 g, 0.038 mol), 1,5-cyclooctadiene (15.22 g, 0.1408 mol of Ni), and THF (55 mL). The dropping funnel is charged with di(n-butyl)magnesium (0.075 mol) obtained by one of the following three methods: (i) A commercial solution in n-heptane. (ii) The diethyl ether/hexane filtrate from part B above. (iii) A solution of di(n-butyl)magnesium (10.39 g, 0.075 mol) in THF (100 mL). (Note: Solid di(n-butyl)magnesium dissolves slowly in THF to give a slightly milky solution.) The reaction flask is cooled to 100 C using an EtOH/N2 bath, and the MgBu2 solution is slowly added dropwise, maintaining the reaction temperature below 80 C. The addition requires approximately 2 h. The color of the reaction mixture turns gradually from green to brownish-yellow over a period of several hours. Upon completeaddition,thereactionmixtureisallowed to reach ambient temperatureandis *

The checkers removed insoluble material via filtration through a pad of dry Celite. The resulting solution was used for the synthesis of Ni(cod)2 and transferred into the dropping funnel. The di(n-butyl) magnesium solution in diethyl ether/hexane could not be stored > 40 ˚C.

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Organometallic Reagents

stirred overnight. The reaction mixture is evaporated under vacuum, and the brownish residue is cautiously treated with MeOH (100 mL) . The resulting dark yellow suspension is stirred for 10 min and then allowed to settle, and the brown solution is decanted or removed by cannula, leaving a fine yellow solid. (Note: Filtration through Celite is possible in principle, but the frit is easily clogged.) The MeOH washing step is repeated until the decanted solution is very pale. Finally, the yellow material is extracted once each with EtOH (50 mL) and n-pentane (50 mL) and is then dried under vacuum (with protection from light) yielding 9.1 g (0.033 mol, 87%) of Ni (1,5-C8H12)2. This material is usually pure enough for further transformations†. The product can be purified by recrystallization. Solid Ni(cod)2 (1–2 g) is placed on top of a 1-cm layer of Celite on a Schlenk frit that is attached to a 250-mL Schlenk flask. Toluene (50 mL) is added carefully, and the mixture is carefully stirred with a plastic spatula while keeping the Celite settled. (Note: Metal spatulas catalyze decomposition of the compound.) The dark yellow mixture is carefully filtered to give a clear yellow filtrate. The procedure is repeated until the extracts are almost colorless. The resulting filtrate is concentrated under reduced pressure until incipient crystallization. The flask is filled with argon, and the golden yellow solution is slowly treated with ether (50 mL). (Note: If at this stage some brown flaky material is formed, the mixture should be carefully filtered once more.) The mixture is stored overnight at 30 C affording golden yellow crystals that are isolated by removing the supernatant. A second crop can be obtained by concentrating the mother liquor under vacuum to a few milliliters, adding ether (20 mL), and storing the mixture overnight at 30 C. The combined recovery efficiency is usually 60–80%. Anal. Calcd. for C16H24Ni: C, 69.9; H, 8.8%. Found: C, 69.6; H 8.9%. 1 H NMR10 (C6D6): d 2.06 (s, 8H, CH2); 4.29 (s, bd, 4H, CH). The checkers found d 2.08 (s, 8H, CH2); 4.30 (s, 4H, CH). Properties The solid complex decomposes after several minutes in air; solutions decompose in air more rapidly. It is moderately soluble in benzene and THF, but heating these solutions above  60 C leads to decomposition. The solid decomposes at 135–140 C. It is nearly insoluble in diethyl ether and saturated hydrocarbons. The complex is decomposed catalytically by halocarbons,19 and even upon storage under inert gas for a prolonged time, it can decompose turning dark slowly. *

The checkers found that the methanolysis of the reaction mixture is a crucial step in the synthesis. The MeOH used should be rigorously dried and the reaction mixture should be cooled using a iPrOH/CO2 cooling bath ( 78 ˚C). It is important to proceed with the preparation since the reaction mixture decomposes over MeOH after days. For storage, we advice to remove all volatiles in vaccuo. † The checkers obtained 80–85% yield of tan solid that was pure by 1H NMR spectroscopy.

30. Sodium (h5-Cyclopentadienyl)Tris(Dimethylphosphito-P)Cobaltate(III)

125

References 1. A. J. Arduengo, III, S. F. Gamper, J. C. Calabrese, and F. Davidson, J. Am. Chem. Soc. 116, 4391 (1994). 2. R. M. Ceder, J. Granell, G. Muller, M. Font-Bardıa, and X. Solans, Organometallics 14, 5544 (1995). 3. S. Ogoshi, K. Tonomori, M. Oka, and H. Kurosawa, J. Am. Chem. Soc. 128, 7077 (2006). 4. M. J. Tenorio, M. C. Puerta, I. Salcedo, and P. Valerga, J. Chem. Soc., Dalton Trans. 653 (2001). 5. M. Stol, D. J. M. Snelders, M. D. Godbode, R. W. A. Havenith, D. Haddleton, G. Clarkson, M. Lutz, A. L. Spek, G. P. M. van Klink, and G. van Koten, Organometallics 26, 3985 (2007). 6. S. D. Ittel, Inorg. Synth. 28, 98 (1990). 7. F. Guerini and G. Salerno, J. Organomet. Chem. 114, 339 (1976). 8. (a) H. M. Colquhoun, D. J. Thompson, and M. W. Twigg, New Pathways for Organic Synthesis, Plenum Press, London, 1984, p. 389. (b) T. R. Belderraın, D. A. Knight, D. J. Irvine, M. Paneque, M. L. Poveda, and E. Carmona, J. Chem. Soc., Dalton Trans. 1491 (1992). 9. R. A. Schunn, S. D. Ittel, and M. A. Cushing, Inorg. Synth. 28, 94 (1990). 10. D. J. Krysan and P. B. Mackenzie, J. Org. Chem. 55, 4229 (1990). 11. C. W. Kamienski and J. F. Eastham, J. Organomet. Chem. 8, 542 (1967). 12. Y. Saheki, K. Sasada, N. Satoh, N. Kawaichi, and K. Negoro, Chem. Lett. 2299 (1987). 13. W. Strohmeier and F. Seifert, Chem. Ber. 94, 2356 (1961). 14. K. L€ uhder, D. Nehls, and K. Majeda, J. Prakt. Chem. 325, 1027 (1983). 15. B. Bogdanovic, P. Bons, S. Konstantinovic, M. Schwickardi, and U. Westeppe, Chem. Ber. 126, 1371 (1993). 16. W. L. F. Armarego and D. D. Perrin, Purification of Laboratory Chemicals, 4th ed., Butterworth/ Heinemann, Oxford, 1996. 17. D. F. Shriver and M. A. Drezdon, The Manipulation of Air-Sensitive Compounds, Wiley, Chichester, 1986. 18. R. B. King, in Organometallic Syntheses, J. J. Eischand R. B. King, eds., Academic Press, Inc., New York, 1965, Vol. 1. 19. C. A. Tolman, D. W. Reutter, and W. C. Seidel, J. Organomet. Chem. 117, C30 (1976).

30. SODIUM (h5-CYCLOPENTADIENYL)TRIS (DIMETHYLPHOSPHITO-P)COBALTATE(III), Na[(C5H5)Co{P(O)(OMe)2}3] €  and PETER C. KUNZ Submitted by WOLFGANG KLAUI Checked by SABINE N. SEIDEL† and JOHN A. GLADYSZz

The chemistry of cobaltocene is dominated by its tendency to act as an electron-rich radical that can undergo one-electron oxidation, ring addition, *

Lehrstuhl I: Bioanorganische Chemie und Katalyse, Heinrich-Heine-Universit€at D€usseldorf, 40225 D€ usseldorf, Germany . † Lehrst€ uhle f€ ur Anorganische Chemie, 91058 Erlangen, Germany . z Department of Chemistry, Texas A&M University, College Station, TX .

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Organometallic Reagents

and ring substitution reactions. Secondary phosphites HP(O)(OR)2 react with cobaltocene in a complex manner that includes both oxidation and ring substitution to produce mixed-valence trinuclear cobalt complexes of the type [Co ((C5H5)Co{P(O)(OR)2}3)2]. This reaction is synthetically valuable since it gives ready access to the anionic complexes [(C5H5)Co{P(O)(OR)2}3] , a versatile class of tripodal oxygen ligands. An important feature of these ligands is their inertness and their high tendency to form complexes with main-group and transition metals. In addition, they can stabilize a large variety of organometallic fragments.1,2 A. [Co((C5H5)Co{P(O)(OMe)2}3)2], Co(LOMe)2 3 CoCp2 þ6 HPðOÞðOMeÞ2 !½CoððC5 H5 ÞCofPðOÞðOMeÞ2 g3 Þ2 Šþ4HCpþH2 Procedure Freshly sublimed cobaltocene (25 g, 0.13 mol) and 44 mL (0.48 mol) of dimethyl phosphite, HP(O)(OMe)2, are added under a nitrogen atmosphere to a 250-mL round-bottomed Schlenk flask equipped with a magnetic stirring bar. A reflux condenser equipped with a pressure relief valve is attached to the Schlenk flask and the apparatus is purged with dry nitrogen. The reflux condenser need not to be connected to water cooling; it is used as a splash guard. The oil bath temperature is set to 100–120 C. After about 1 h, cyclopentadiene that is formed in the reaction starts refluxing and orange crystals form. After several hours, the brown color of cobaltocene disappears, but the solution is still dark. The heating is switched off and the apparatus kept in the oil bath that slowly cools overnight. The air-stable product forms as large orange crystals that are filtered off, washed with ethanol and pentane, and dried in vacuo. The yield is 40 g (42 mmol, 94%). Properties [Co((C5H5)Co{P(O)(OMe)2}3)2] is thermally stable up to 300 C, paramagnetic, and soluble in chlorinated solvents and in strong acids.3 The infrared spectrum (KBr wafer) has medium to strong absorptions at 2980, 2840, 1425, 1175, 1125, 1035, 1005, 835, and 585 cm 1. B. Na[(C5H5)Co{P(O)(OMe)2}3], NaLOMe 2 ½CoððC5 H5 ÞCofPðOÞðOMeÞ2 g 3 Þ2 Š þ 12 NaCN þ 0:5O2 þ H2 O ! 4 Na½ðC5 H5 ÞCofPðOÞðOMeÞ2 g3 Š þ 2 Na3 ½CoðCNÞ6 Š þ 2 NaOH

30. Sodium (h5-Cyclopentadienyl)Tris(Dimethylphosphito-P)Cobaltate(III)

127

Procedure4 Co(LOMe)2 (40 g, 42 mmol) is suspended in 350 mL of methanol in a 1-L threenecked round-bottomed flask equipped with a thermometer and a gas inlet with a porous frit. The suspension is cooled to 10 to 5 C in an acetone/ice bath. A vigorous stream of pressurized air is bubbled through the suspension. Sodium cyanide (14 g, 0.29 mol) is then added slowly to the suspension in small portions over the course of 1 h. The reaction mixture is stirred for one more hour, and then the solvent is removed using a rotary evaporator and the residue dried in vacuo. The resulting yellow solid is transferred to a Soxhlet apparatus and the sodium salt of the tripodal oxygen ligand, NaLOMe, is separated from the sodium salts Na3[Co(CN)6] and NaCN by extraction with dichloromethane. The extraction requires several days. Rotary evaporation of the extract followed by drying in vacuo leaves NaLOMe as bright yellow powder. The yield is 36–38 g (76–80 mmol, 91–96%). The product is pure enough for most purposes. If necessary, it can be dissolved in twice distilled water, and the solution filtered through a membrane followed by evaporation at room temperature. Single crystals of a coordination polymer of NaLOMe have been obtained by slow diffusion of pentane into a solution of NaLOMe in dry dichloromethane.5 P{1 H} NMR (CDCl3): d 111 (s). 1 H NMR (CDCl3): 3.6 (virt. q, 18H, J HCOP ¼ 11 Hz, OCH3), 5.1 (q, 5H, 3 J HCCoP ¼ 0:5 Hz, C5H5). IR (KBr): medium to strong absorptions at 2835, 1430, 1170, 1080, 835, 750, 580 cm 1.

31 3

Properties The tripodal oxygen ligand NaLOMe is very soluble in water and methanol, but only very slightly soluble in acetone, diethyl ether, and pentane. Freshly precipitated NaLOMe is soluble in CH2Cl2, but recrystallized solid is not. The sodium salt of the corresponding ligand [LOEt] , [(C5H5)Co{P(O) (OEt)2}3] , prepared analogously from cobaltocene and HP(O)(OEt)2, crystal-

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lizes from water as 3NaLOEt4H2O.6 It is much more soluble in organic solvents, even in pentane, as well as in water. For sterically demanding ligands such as [LOPh] , other synthetic routes are available.7 Tripodal oxygen ligands of the type [(C5R0 5)M{P(O)(OMe)2}3] with M ¼ Rh or Ir and R0 ¼ H, CH3 are accessible via Michaelis–Arbuzov reactions of Rh(III) and Ir(III) complexes with trimethylphosphite.8,9 References W. Kl€aui, Angew. Chem. 102, 661–670 (1990); Angew. Chem., Int. Ed. Engl. 29, 627–637 (1990). W.-H. Leung, Q.-F. Zhang, and X.-Y. Yi, Coord. Chem. Rev. 251, 2266–2279 (2007). W. Kl€aui, H. Neukomm, H. Werner, and G. Huttner, Chem. Ber. 110, 2283–2289 (1977). W. Kl€aui, B. Lenders, B. Hessner, and K. Evertz, Organometallics 7, 1357–1363 (1988). W. Kl€aui, D. Matt, F. Balegroune, and D. Grandjean, Acta Crystallogr. C 47, 1614–1617 (1991). W. Kl€aui, A. M€ uller, W. Eberspach, R. Boese, and I. Goldberg, J. Am. Chem. Soc. 109, 164–169 (1987). 7. W. Kl€aui, H.-O. Asbahr, G. Schramm, and U. Englert, Chem. Ber. 130, 1223–1229 (1997). 8. W. Kl€aui, H. Otto, W. Eberspach, and E. Buchholz, Chem. Ber. 115, 1922–1933 (1982) 9. M. Scotti, M. Valderrama, P. Campos, and W. Kl€aui, Inorg. Chim. Acta 207, 141–145 (1993).

1. 2. 3. 4. 5. 6.

Chapter Seven

BIO-INSPIRED IRON AND NICKEL COMPLEXES 31. IRON–CYANOCARBONYL COMPLEXES [PPN][Fe(CO)4(CN)] AND [PPN][FeBr(CO)3(CN)2] Submitted by CHIEN-HONG CHEN* and WEN-FENG LIAW† Checked by C. MATTHEW WHALEYz and THOMAS B. RAUCHFUSSz

The iron motif of the active-site structures of [NiFe]-hydrogenases isolated from D. gigas, D. vulgaris, D. fructosovorans, and D. desulfuricans ATCC27774 has been established as a square pyramidal [Fe(CN)2(CO)(Scys)2] in the reduced state based on the single-crystal X-ray diffraction and infrared spectroscopy.1–4 The structural information inspired the bioinorganic/bioorganometallic chemists to synthesize the model complexes that closely mimic the features of the Ni-A, Ni-B, Ni-R, and Ni-SIa states of the catalytic cycle of [NiFe]-hydrogenases. Synthetic approaches to iron–thiolate cyanocarbonyl complexes, to our best knowledge, involve (i) substitution of the carbon monoxide (CO) with cyanide (CN ) from iron–thiolate carbonyl complexes, (ii) reaction of iron salt, cyanide salt, and thiolate under carbon monoxide atmosphere, and (iii) purge of carbon monoxide through the solution of iron–thiolate–cyano complexes. Based on these synthetic methods, a few mononuclear iron–thiolate cyanocarbonyl compounds [Fe(CN)2(CO)(S2C6H4-S,S)]2 ,5 [(PS3)Fe(CN)(CO)]2 (PS3H3 ¼ tris(2-phenylthiol)phosphine),6 and [(S3)Fe(CN)2(CO)]2 *

School of Applied Chemistry, Chung Shan Medical University, Taichung, Taiwan. Department of Chemistry, National Tsing Hua University, Hsinchu 30043, Taiwan. z Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801. †

Inorganic Syntheses, Volume 35, edited by Thomas B. Rauchfuss Copyright Ó 2010 John Wiley & Sons, Inc. 129

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(S3 ¼ bis(2-mercaptophenyl)sulfide(2 ))7 have been reported by Rauchfuss et al., Koch et al., and Sellmann et al., respectively.

In addition to the above synthetic strategies, complex [FeIIBr(CO)3(CN)2] , obtained from oxidative addition of BrCN to [Fe(CO)4(CN)] (as shown below), serves as a useful precursor to synthesize a series of iron(II)–thiolate cyanocarbonyl complexes [Fe(CN)2(CO)2(S2CR-S,S)] , [Fe(CN)2(CO)(S2CR-S, S)] (R ¼ OEt, NEt2),8cis,cis-[Fe(CO)2(CN)2(CS3-S,S)]2 , cis-[Fe(CO)2(CN) (pdt ¼ 1,3(S(CH2)2 S(CH2)2S-S,S,S)] ,9 and [Fe(CO)2(CN)2(pdt)K] propanedithiolate).10 A. BIS(TRIPHENYLPHOSPHORANYLIDENE)AMMONIUM TETRACARBONYLCYANOFERRATE(0), [PPN][Fe(CO)4(CN)] FeðCOÞ5 þ NaNðSiMe3 Þ2 ! Na½FeðCNÞðCOÞ4 Š þ OðSiMe3 Þ2 Na½FeðCNÞðCOÞ4 Š þ ½PPNŠCl ! PPN½FeðCNÞðCOÞ4 Š þ NaCl & Caution. Fe(CO)5is extremely toxic on account of the high volatility. All work must be carried out in a well-ventilated fume hood. Procedure A 1 M THF solution of NaN(SiMe3)2 (5 mL) is added dropwise by syringe to the solution containing Fe(CO)5 (5 mmol, 0.65 mL) in THF (15 mL). The resulting red solution is stirred for 8 h under N2 atmosphere at room temperature and then transferred to another 50-mL Schlenk flask loaded with [PPN]Cl (5 mmol, 2.87 g) by cannula under a positive pressure of N2. After stirring for another 8 h at room temperature, the reaction mixture is filtered through Celite to remove NaCl. The filtrate is concentrated to 5 mL under vacuum, and diethyl ether (40 mL) is added to precipitate the white solid. The white solid is washed with diethyl ether (15 mL) twice and recrystallized by dissolution in THF (10 mL) followed by the addition of hexanes (30 mL) to give the white solid PPN[Fe(CO)4(CN)].11,12 Yield: 0.255 g (68%). IR (THF): 2112 (vw), 2033 (w), 1924(s) cm 1. Properties The white microcrystalline [PPN][Fe(CO)4(CN)] is moderately air sensitive and should be handled under an inert atmosphere. Complex PPN[Fe(CO)4(CN)] is readily soluble in THF, acetonitrile, and dichloromethane.

31. Iron–Cyanocarbonyl Complexes[PPN][Fe(CO)4(CN)] and [PPN][FeBr(CO)3(CN)2]

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B. BIS(TRIPHENYLPHOSPHORANYLIDENE)AMMONIUM BROMOTRICARBONYLCYANOFERRATE(II), [PPN][FeIIBr(CO)3(CN)2] PPN½FeðCNÞðCOÞ4 Š þ BrCN ! PPN½FeBrðCNÞ2 ðCOÞ3 Š þ CO & Caution. Cyanogen bromide (BrCN) (5 M acetonitrile solution or solid) is corrosive, volatile (fumes in air), and toxic. Use safety gloves and goggles, avoid inhalations of vapors, and conduct all operations in a well-ventilated hood far from ignition sources. Procedure In a 50-mL Schlenk flask is prepared a stirred solution of PPN[Fe(CO)4(CN)] (0.5 mmol, 0.365 g) in THF (8 mL) sealed with a rubber septum. This solution is treated dropwise with 120 mL of a 5 M solution of BrCN (0.6 mmol) in MeCN. The oxidative reaction is immediately indicated by evolution of CO gas. At this time, a needle is quickly inserted into the rubber septum to release the CO gas. After 30 min of stirring at room temperature, the reaction mixture is filtered through Celite and hexane (25 mL) is added to precipitate the light yellow solid. Recrystallization by dissolution in THF (10 mL) followed by the addition of diethyl ether (50 mL) gives the light yellow solid [PPN][FeBr(CO)3(CN)2]. Yield: 0.277 g (68%). Anal. Calcd. for C41H30BrFeN3O3P2: C, 60.77; H, 3.73; N, 5.19. Found: C, 60.88; H, 4.03; N, 4.96. IR (THF): 2139 (vw), 2127 (vw) 2099 (m), 2056 (s), 2035 (m) cm 1. UV–vis (THF, e in cm 1 M 1): 325 (1990), 383 (658) nm. Properties The light yellow microcrystalline [PPN][FeBr(CO)3(CN)2] is moderately air sensitive and reacts slowly with air to yield an impure light yellow solid. Complex [PPN][FeBr(CO)3(CN)2] is readily soluble in organic solvents, such as tetrahydrofuran, acetonitrile, and dichloromethane. Although THF solution of complex [PPN][FeBr(CO)3(CN)2] is moderately air sensitive at room temperature, it should be handled under an inert atmosphere. References 1. (a) A. Volbeda, M.-H. Charon, C. Piras, E. C. Hatchikian, M. Frey, and J. C. Fontecilla-Camps, Nature 373, 580 (1995). (b) E. Garcin, X. Vernede, E. C. Hatchikian, A. Volbeda, M. Frey, and J. C.

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2.

3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Bio-Inspired Iron and Nickel Complexes Fontecilla-Camps, Structure (London) 7, 557 (1999). (c) R. Happe, W. Rosenboom, A. J. Pierik, S. P. J. Albracht, and K. A. Bagley, Nature 385, 126 (1997). (d) A. Volbeda, E. Garcin, C. Piras, A. L. de Lacey, V. M. Fernandez, E. C. Hatchikian, M. Frey, and J. C. Fontecilla-Camps, J. Am. Chem. Soc. 118, 12989 (1996). (e) A. Volbeda, L. Martin, C. Cavazza, M. Matho, B. W. Faber, W. Roseboom, S. P. J. Albracht, E. Garcin, M. Rousset, and J. C. Fontecilla-Camps, J. Biol. Inorg. Chem. 10, 239 (2005). (a) Y. Higuchi, H. Ogata, K. Miki, N. Yasuoka, and T. Yagi, Structure (London) 7, 549 (1999). (b) Y. Higuchi, T. Yagi, and N. Yasuoka, Structure (London) 5, 1671 (1997). (c) H. Ogata, Y. Mizoguchi, N. Mizuno, K. Miki, S.-I. Adachi, N. Yasuoka, T. Yagi, O. Yamauchi, S. Hirota, and Y. Higuchi, J. Am. Chem. Soc. 124, 11628 (2002). (d) S. Foerster, M. Stein, M. Brecht, H. Ogata, Y. Higuchi, and W. Lubitz, J. Am. Chem. Soc. 125, 83 (2003). (e) H. Ogata, S. Hirota, A. Nakahara, H. Komori, N. Shibata, T. Kato, K. Kano, and Y. Higuchi, Structure (Cambridge, MA) 13, 1635 (2005). M. Rousset, Y. Montet, B. Guigliarelli, N. Forget, M. Asso, P. Bertrand, J. C. Fontecilla-Camps, and E. C. Hatchikian, Proc. Natl. Acad. Sci. USA. 95, 11625 (1998). P. M. Matias, C. M. Soares, L. M. Saraiva, R. Coelho, J. Morais, J. Le Gall, and M. A. Carrondo, J. Biol. Inorg. Chem. 6, 63 (2001). T. B. Rauchfuss, S. M. Contakes, S. C. Hsu, M. A. Reynolds, and S. R. Wilson, J. Am. Chem. Soc. 123, 6933 (2001). H.-F. Hsu, S. A. Koch, C. V. Popescu, and E. M€unck, J. Am. Chem. Soc. 119, 8371 (1997). D. Sellmann, F. Geipel, and F. W. Heinemann, Chem. Eur. J. 8, 958 (2002). W.-F. Liaw, J.-H. Lee, H.-B. Gau, C.-H. Chen, S.-J. Jung, C.-H. Hung, W.-Y. Chen, C.-H. Hu, and G.-H. Lee, J. Am. Chem. Soc. 124, 1680 (2002). C.-H. Chen, Y.-S. Chang, C.-Y. Yang, T.-N. Chen, C.-M. Lee, and W.-F. Liaw, Dalton Trans. 137 (2004). Z. Li, Y. Ohki, and K. Tatsumi, J. Am. Chem. Soc. 127, 8950 (2005). J. K. Ruff, Inorg. Chem. 8, 86 (1969). S. A. Goldfield and K. N. Raymond, Inorg. Chem. 13, 770 (1974).

32. NICKEL COMPLEXES OF BIS (DIETHYLPHOSPHINOMETHYL)METHYLAMINE Submitted by DANIEL L. DUBOIS* and MARY RAKOWSKI DUBOIS* Checked by MARK R. RINGENBERG† and THOMAS B. RAUCHFUSS†

Several types of phosphine ligands that incorporate an amine base have been synthesized. As illustrated in the selected leading references, studies of the metal complexes of these ligands have shown that in some cases the base can participate in small-molecule activation and hydrogen bonding interactions.1–6 In one large class of mixed phosphine–amine ligands, prepared by Mannich-type reactions, a *

Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352 † Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801

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methylene group separates the two heteroatoms.7 A simple example of this ligand type is a 1,3-diphosphine with a noncoordinating amine incorporated into the chelate ring backbone, bis(diethylphosphinomethyl)methylamine (PNP). The ligand is readily prepared in a high-yield, one-flask procedure over a period of 5–6 h by the reaction of diethylphosphine with aqueous formaldehyde, followed by addition of methylamine. Complexes of this ligand with several metal ions have been synthesized and studied.8 The pKa of the protonated pendant amine in several PNP complexes has been determined to lie in the range of 9–11 in acetonitrile, depending on the nature of the metal ion and other ligands. The nickel PNP derivatives are of special interest because of the extensive thermodynamic data available for these and related nickel diphosphines.9 In the Ni(II) derivative, [Ni(PNP)2]2þ , the hydride acceptor ability of the metal ion is well matched with the proton acceptor ability of the pendant base. As a result, the complex reacts readily with hydrogen (1 atm) to form the heterolytic cleavage product [HNi(PNHP)PNP]2þ .8a The pendant base in the PNP ligand has been found to function as a very effective proton relay. Rapid intramolecular M–H/N–H exchange and intermolecular proton/hydride exchange have been characterized. This contribution describes the procedures for the syntheses of the PNP ligand, Ni(PNP)2, and its protonation to form [HNi(PNP)2]PF6 and [Ni(PNP)2](BF4)2. All reactions are performed under an inert atmosphere using standard Schlenk techniques, and all solvents are dried and degassed by standard procedures before use. Starting materials are reagent-grade commercially available compounds, with the exception of [Ni(MeCN)6](BF4)20.5MeCN, which is prepared by a previously reported procedure.10 A. BIS(DIETHYLPHOSPHINOMETHYL)METHYLAMINE 2 Et2 PH þ 2 CH2 O þ ½MeNH3 ŠCl þ Et3 N ! ðEt2 PCH2 Þ2 NMe þ 2 H2 O þ ½Et3 NHŠCl Procedure & Caution. Diethylphosphine is a pyrophoric liquid that must be handled under rigorously anaerobic conditions.

A 250-mL Schlenk flask is charged with diethylphosphine (2.27 g, 25.2 mmol) and degassed aqueous formaldehyde (37 wt%, 1.95 mL, 26 mmol) in ethanol (10 mL), and the solution is stirred for 30 min. A solution of hydrochloride salt of methylamine (MeNH3Cl, 0.85 g, 12.65 mmol) in an ethanol/water solution (10 mL, 3:1 ratio) is added by cannula or syringe to the phosphine solution. Finally, triethylamine (2 mL, 14 mmol) is added to deprotonate the methylamine salt. The

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mixture is stirred at room temperature for 3 h, and the solvent is then removed in vacuo. The remaining solid is extracted with diethyl ether (3  25 mL). Removal of the solvent from the combined extracts results in isolation of the product as a colorless liquid. Yield: 2.12 g (71%). Anal. Calcd. for C11H27NP2: C, 56.15; H, 11.57; N, 5.95; P, 26.33. Found: C, 55.73; H, 12.22; N, 5.78; P, 25.76. 1 H NMR (CD3CN): d 2.62 (d, 2 J PH ¼ 2:1 Hz, PCH2N); 2.36 (s, NCH3); 1.37 (q, 3 J PH ¼ 7:8 Hz, PCH2CH3); 1.02 (d of tr, 3 J PH ¼ 14:1 Hz, PCH2CH3). 31 P NMR (vs. external H3PO4, CD3CN): d 30.99 (s). Properties The PNP ligand is an air-sensitive, clear high-boiling liquid that is soluble in most organic solvents. It can be characterized by its 1 H and 31 P NMR spectra. B. BIS(BIS(DIETHYLPHOSPHINOMETHYL)METHYLAMINE) NICKEL(0), Ni(PNP)2 2 ðEt2 PCH2 Þ2 NMe þ NiðCODÞ2 ! Ni½ðEt2 PCH2 Þ2 NMeŠ2 þ 2 COD Procedure Solid Ni(COD)2 (0.76 g, 2.76 mmol) is added to a solution of PNP (2.30 g, 5. 52 mmol) in tetrahydrofuran (60 mL) that has been cooled to 80 C using a dry ice/isopropanol bath. The resulting suspension is allowed to warm to room temperature while stirring over a period of ca. 1 h. Solvent is removed from the light yellow solution under vacuum to produce the product as a white solid. The solid is washed with acetonitrile (10 mL) and dried again under vacuum to give an analytically pure product. Yield: 1.2 g (81%). Anal. Calcd. for C22H54N2P4Ni: C, 49.93; H, 10.28; N, 5.29. Found: C, 49.15; H, 10.36; N, 4.96. 1 H NMR (toluene-d8): d 2.42 (s, PCH2N); 2.22 (s, NCH3); 1.31 and 1.65 (m, PCH2CH3); 1.05 (m, PCH2CH3). 31 P NMR (vs. external H3PO4, toluened8): d 6.60 (s). Properties Ni(PNP)2 is a white, air-sensitive solid that is soluble in nonpolar organic solvents. C. HYDRIDOBIS(PNP)NICKEL(II) HEXAFLUOROPHOSPHATE NiððEt2 PCH2 Þ2 NMeÞ2 þ NH4 PF6 ! ½HNiððEt2 PCH2 Þ2 NMeÞ2 ŠPF6 þ NH3

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Procedure A solution of ammonium hexafluorophosphate (NH4PF6) (0.20 g, 1.23 mmol) in absolute ethanol (10 mL) is filtered, purged with nitrogen, and added to a solution of Ni(PNP)2 (0.30 g, 0.57 mmol) in tetrahydrofuran (30 mL) under nitrogen at room temperature. The resulting yellow solution is stirred for 0.5 h, and the volume is reduced to 10 mL. Yellow needles form when this solution is placed in a freezer overnight. These are collected by filtration and dried under vacuum. Yield: 0.20 g (51%). Anal. Calcd. for C22H55F6N2NiP5: C, 39.13; H, 8.21; N, 4.15. Found: C, 38.05; H, 8.14; N, 4.13. 1 H NMR (CD3CN): d 2.70 (s, PCH2N); 2.38 (s, NCH3); 1.62 and 1.72 (m, PCH2CH3); 1.06 (m, PCH2CH3); 14.75 (pentet, 2 J PH ¼ 6.3 Hz, NiH). 31 P NMR (CD3CN): d 5.46 (s). IR (Nujol mull): 1933 cm 1 (nNi–H). Properties [HNi(PNP)2](PF6) is an air-sensitive yellow crystalline material. It is soluble in polar organic solvents such as acetonitrile and acetone. D. BIS(PNP)NICKEL(II) TETRAFLUOROBORATE ½NiðMeCNÞ6 ŠðBF4 Þ2 þ 2 ðEt2 PCH2 Þ2 NMe ! ½NiððEt2 PCH2 Þ2 NMeÞ2 ŠðBF4 Þ2 þ 6 MeCN Procedure Solid [Ni(MeCN)6](BF4)20.5MeCN (0.62 g, 1.25 mmol) is added to a solution of PNP (0.59 g, 2.50 mmol) in acetonitrile (30 mL). The resulting deep red solution is stirred at room temperature for 1 h. Removal of the solvent under vacuum results in a red powder, which is washed with hexanes (50 mL) and dried in a vacuum. Yield: 0.74 g (74%). Anal. Calcd. for C22H54N2B2F8NiP4: C, 37.59; H, 7.74; N, 3.99. Found: C, 36.92; H, 7.69; N, 3.99. 1 H NMR (CD3CN): d 2.87 (s, PCH2N); 2.44 (s, NCH3); 2.0 (m, PCH2CH3); 1.21 (m, PCH2CH3). 31 P NMR (CD3CN): d 1.70 (s). Properties [Ni(PNP)2](BF4)2 is an air-sensitive red solid that is soluble in acetonitrile, dichloromethane, and acetone. The product tends to undergo slow decomposition in solution, and recrystallization was not effective. The cyclic voltammogram

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using a glassy carbon electrode in acetonitrile with 0.2 M Et4NBF4 shows reversible one-electron reductions at 0.64 (NiII/I) and 1.24 V (NiI/0) vs. the ferrocenium/ferrocene couple. When a CD3CN solution of [Ni(PNP)2](BF4)2 (25 mg) in an NMR tube is purged with hydrogen at room temperature, a color change from red to yellow is observed, and the formation of [HNi(PNHP)(PNP)] (BF4)2 is observed by NMR spectroscopy to be complete within 10 min as shown in the equation. The hydrogen addition product is characterized by 1 H and 31 P NMR spectroscopies. 1 H NMR (CD3CN): d 3.10 (br s, PCH2N); 2.78 (br s, NCH3); 1.82 and 1.72 (m PCH2CH3); 1.07 (m, PCH2CH3); 3.35 (br s, average of rapidly exchanging Ni–H and N–H). 31 P NMR (CD3CN): d 7.25 (s).

Acknowledgment The Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy. References 1. (a) L. Morello, M. J. Ferreira, B. O. Patrick, and M. D. Fryzuk, Inorg. Chem. 47, 1319 (2008). (b) E. A. MacLachlan, F. M. Hess, B. O. Patrick, and M. D. Fryzuk, J. Am. Chem. Soc. 129, 10895 (2007). 2. (a) T. Li, I. Bergner, F. N. Haque, M. Zimmer-De Iuliis, D. Song, and R. H. Morris, Organometallics 26, 5940 (2007). (b) T. Li, R. Churlaud, A. J. Lough, K. Abdur-Rashid, and R. H. Morris, Organometallics 23, 6239 (2004). 3. M. Jimenez-Tenorio, M. D. Palacios, M. C. Puerta, and P. Valerga, Organometallics 24, 3088 (2005). 4. (a) A. Choualeb, A. J. Lough, and D. G. Gusev, Organometallics 26, 3509 (2007). (b) Z. E. Clarke, P. T. Maragh, T. P. Dasgupta, D. G. Gusev, A. J. Lough, and K. Abdur-Rashid, Organometallics 25, 4113 (2006). 5. (a) B. J. Fullmer, J. Fan, M. Pink, and K. G. Caulton, Inorg. Chem. 47, 1865 (2008). (b) M. Ingleson, J. Fan, M. Pink, J. Tomaszewski, and K. G. Caulton, J. Am. Chem. Soc. 128, 1804 (2006). 6. (a) D. B. Grotjahn, Chem. Eur. J. 11, 7146 (2005). (b) D. B. Grotjahn, V. Miranda-Soto, E. J. Kragulj, D. A. Lev, G. Erdogan, X. Zeng, and A. L. Cooksy, J. Am. Chem. Soc. 130, 20 (2008). 7. (a) K. Moedritzer and R. R. Irani, J. Org. Chem. 31, 1603–1607 (1966).(b) L. J. Matienzo and S. O. Grim, in Inorganic Syntheses, F. Basolo, ed., McGraw-Hill, New York, 1976, Vol. 16, pp. 198–199. 8. (a) C. J. Curtis, A. Miedaner, R. Ciancanelli, W. W. Ellis, B. C. Noll, M. Rakowski DuBois, and D. L. DuBois, Inorg. Chem. 42, 216 (2003). (b) C. J. Curtis, A. Miedaner, J. W. Raebiger, and D. L. DuBois, Orgnometallics 23, 511 (2004). (c) R. M. Henry, R. K. Shoemaker, R. H. Newell, G. M. Jacobsen, D. L. DuBois, and M. Rakowski DuBois, Organometallics 24, 2481–2491 (2005). (d) R. M. Henry, R. K. Shoemaker, D. L. DuBois, and M. Rakowski DuBois, J. Am. Chem. Soc. 128,

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3002 (2006). (e) G. M. Jacobsen, R. K. Shoemaker, M. Rakowski DuBois, and D. L. DuBois, Organometallics 26, 4964 (2007). (f) G. M. Jacobsen, J. Yang, B. Twamley, A. D. Wilson, M. Bullock, M. Rakowski DuBois, and D. L. DuBois, Energy Environ. Sci. 1, 167 (2008). 9. (a) D. E. Berning, B. C. Noll, and D. L. DuBois, J. Am. Chem. Soc. 121, 11432 (1999). (b) C. J. Curtis, A. Miedaner, W. W. Ellis, and D. L. DuBois, J. Am. Chem. Soc. 124, 1918 (2002). (c) D. E. Berning, A. Miedaner, C. J. Curtis, B. C. Noll, M. Rakowski DuBois, and D. L. DuBois, Organometallics 20 1832 (2001). 10. (a) B. J. Hathaway, D. G. Holah, and A. E. Underhill, J. Chem. Soc. 2444 (1962).

33. MONOMERIC IRON(II) COMPLEXES HAVING TWO STERICALLY HINDERED ARYLTHIOLATES Submitted by YASUHIRO OHKI,* SHUN OHTA,* and KAZUYUKI TATSUMI* Checked by LUKE M. DAVIS,† GREGORY S. GIROLAMI,† AARON M. ROYER,† and THOMAS B. RAUCHFUSS†

Iron–thiolate complexes serve as starting materials for synthetic analogues of iron–sulfur clusters in proteins. The chemistry of iron(II)–thiolate complexes generally starts with iron halides (FeX2; X ¼ Cl, Br, I) and thiolate salts, and such a reaction usually produces the tetrakis-thiolate complex, [Fe(SR)4]2 (R ¼ alkyl or aryl groups).1,2 Whereas [Fe(SR)4]2 have been extensively used in the preparation of ferredoxin models,1,2 bis-thiolate complexes of iron, [Fe(SAr)2]n (Ar ¼ bulky aryl groups, n ¼ 1 or 2), recently appeared to serve as precursors for iron–sulfur clusters relevant to the nitrogenase active sites.3 The metal centers in [Fe(SAr)2]n are coordinatively and electronically unsaturated, and thus they also serve as potential reaction sites. For instance, Henkel and coworkers have demonstrated that the iron center in {Fe[SC6H3-2,6-(SiMe3)2]2}2 reacts with CH3CN or OPEt3 to form {Fe[SC6H3-2,6-(SiMe3)2]2(CH3CN)}2 or Fe[SC6H32,6-(SiMe3)2]2(OPEt3), respectively.4 Herein, we describe a facile synthetic procedure for iron(II) bis-thiolate complexes having sterically hindered thiolate groups. The preparation uses bis(trimethylsilylamido)iron(II), which is prepared by a modification of the procedure of Andersen et al.5 General Considerations Manipulations are carried out under a nitrogen atmosphere using standard Schlenk techniques unless otherwise noted. Compounds from commercial suppliers are used without further purification, but elemental sulfur is crystallized from hot *

Department of Chemistry, Graduate School of Science, and Research Center for Materials Science, Nagoya University, Nagoya 464-8602, Japan † Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801

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toluene. Anhydrous FeCl2 is gradually hydrolyzed and oxidized under air and thus should be stored under an inert atmosphere. Solvents were distilled from sodium–benzophenone or purified by passing over columns of a supported copper catalyst and activated alumina.6 A. BIS[BIS(TRIMETHYLSILYL)AMIDO]IRON(II) FeCl2 þ 2 LiNðSiMe3 Þ2 ! Fe½NðSiMe3 Þ2 Š2 þ 2 LiCl Procedure* According to the procedure of Amonoo-Neizer et al.,7 lithium bis(trimethylsilyl) amide is prepared from 1,1,1,3,3,3-hexamethyldisilazane (7.0 mL, 32 mmol) and a hexane solution of n-butyllithium (1.56 M, 21 mL, 32 mmol) in a 100-mL twonecked round-bottomed flask with a stirring bar, a three-way stopcock, and a glass stopper. (Caution: Butyllithium must be handled with care under an inert atmosphere.) The resultant solution of lithium bis(trimethylsilyl)amide is evaporated until dryness under reduced pressure. The flask with a white solid of LiN (SiMe3)2 is cooled with an ice bath and 25 mL of diethyl ether is carefully added via syringe to dissolve the solid.† (Caution: Lithium bis(trimethylsilyl)amide must be handled with care under an inert atmosphere.) The glass stopper is removed from the flask under nitrogen flow, and FeCl2 (2.05 g, 16 mmol) is quickly added to the flask via funnel. As soon as the addition is completed, the flask is closed with the glass stopper. The ice bath is removed, and the mixture is allowed to warm to room temperature with stirring for 12 h. The color of reaction mixture turns from dark brown to green during the course of the reaction.z The solvent is removed under reduced pressure to afford an oily green solid. The flask is taken into a glovebox, and 20 mL of hexane is added to the flask. The dark green suspension is filtered, and then the dark green solution is transferred to the left side of the H-shaped glassware shown in Fig. 1.§ A stirring bar is dropped into *

The checkers prefer the preparation of lithium bis(trimethylsilyl)amide by Bradley and Copperthwaite (Inorg. Synth. 18, 112–120 (1978)). The checkers also found that commercial lithium bis(trimethylsilyl)amide solution in hexanes could be used with good results. † The checkers found that the solubility of lithium bis(trimethylsilyl)amide salt in diethyl ether was limited, and a slurry rather than a solution resulted in this step. z The checkers found that the solution remained dark brown and did not turn green. § To avoid repeated trips into the glovebox, the checkers instead added dry, deoxygenated hexane to the reaction vessel through a rubber septum, and then transferred the green solution through a filter cannula to a round-bottomed Schlenk flask. Several such extractions (in 20-mL portions) were necessary to obtain a good yield of product. After the solvent was removed from the combined extracts, the product was distilled from the oily residue under vacuum through a short elbow to a second Schlenk flask.

33. Monomeric Iron(II) Complexes Having Two Sterically Hindered Arylthiolates

139

Figure 1. Apparatus for distillation of Fe[N(SiMe3)2]2.

the green solution, and a glass stopper and a J. Young tap are attached to the glassware, and then the glassware is taken out from the glovebox. The solvent is removed under reduced pressure at room temperature, leaving a dark green oil. After completion of the removal of hexane, the resultant green oil is distilled to the other side of the glassware at 90–100 C under 0.01 mmHg. The J. Young tap is closed, and the glassware is taken into a glovebox to collect the product. The product is initially a green oil that solidifies after a few hours at room temperature. Yield: 4.98 g (84%). 1

H NMR (600 MHz, C6D6, 0.33 M, 299K): d 65.6 (CH3).

Properties The iron–amide complex is an extremely air- and moisture-sensitive light green solid and must be stored under a strictly inert atmosphere. Handling in a glovebox

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is recommended. It is very soluble in hexane and toluene, while THF binds to the iron center to produce a three-coordinate THF adduct {(THF)Fe[N(SiMe3)2]2}.8 The product crystallizes as the dimer (mp 36–38 C), but the monomeric form is dominant in solution at room temperature, as indicated by the 1 H NMR spectrum where a single SiMe3 signal is observed at d 65.6. The monomer–dimer equilibrium constants have been evaluated by the temperature-dependent 1 H NMR spectra in toluene-d8.8 Other physicochemical properties have been described.5,8,9 B. 2,6-DI(MESITYL)BENZENETHIOL 2; 4;6-Me3 C6 H2 Br þ Mg ! 2;4;6-Me3 C6 H2 MgBr 1;3-Cl2 C6 H4 þ BuLi ! 1;3-Cl2 C6 H3 -2-Li þ BuH 1;3-Cl2 C6 H3 -2-Li þ 2 2;4;6-Me3 C6 H2 MgBr ! 1;3-ðmesitylÞ2 C6 H3 Li þ 2MgBrCl 1;3-ðmesitylÞ2 C6 H3 Li þ S ! 1;3-ðmesitylÞ2 C6 H3 SLi 1;3-ðmesitylÞ2 C6 H3 SLi þ HCl ! 1;3-ðmesitylÞ2 C6 H3 SH þ LiCl This compound is reported by Power and coworkers.10 The following method using 1,3-dichlorobenzene as the precursor is a modification of the procedure of Saednya and Hart.11 A 500-mL three-necked round-bottomed flask equipped with a 250-mL pressure-equalized dropping funnel, water-cooled reflux condenser, and a magnetic stirring bar is connected via a three-way stopcock to the Schlenk line. After magnesium turnings (3.60 g, 145 mmol) are charged into the flask, the entire apparatus is evacuated and filled with nitrogen three times. Under nitrogen flow, THF (20 mL) is added to the flask, and 1-bromo-2,4,6-trimethylbenzene (22.5 mL, 144 mmol) and THF (200 mL) are charged into the dropping funnel. A THF solution of 1-bromo-2,4,6-trimethylbenzene is added dropwise to magnesium at room temperature, and the solution is kept stirring overnight to generate a THF solution of 2,4,6-Me3C6H2MgBr (A). A 1000-mL three-necked round-bottomed flask with a stirring bar, a three-way stopcock, a 200-mL pressure-equalized dropping funnel, and a reflux condenser is evacuated and filled with nitrogen three times. Under nitrogen flow, 1,3-dichlorobenzene (8.1 mL, 69.6 mmol) and THF (200 mL) are added to the flask and a hexane solution of n-butyllithium (1.57 M, 44 mL, 69.6 mmol) is charged into the dropping funnel. The flask is cooled below 78 C with methanol/liquid nitrogen bath, and the n-butyllithium solution is added dropwise. After being stirred for 1 h below

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141

78 C, a half of the THF solution of 2,4,6-Me3C6H2MgBr (A) is transferred to the dropping funnel via cannula under nitrogen, and A is added dropwise to the flask. Another half of the THF solution of A is successively added below 78 C, and the mixture is stirred at this temperature for 1 h. With stirring, the mixture is allowed to warm to room temperature, and then it is refluxed for 1 h to form a dark brown solution. After cooling to room temperature, the flask is cooled with an ice bath, and sulfur (11.4 g, 355 mmol) is added in small portions under nitrogen to give an orange-brown solution, which is warmed to room temperature and stirred for 3 h. The flask is again cooled with an ice bath, and LiAlH4 (9.43 g, 236 mmol) is added portionwise. (Caution: Lithium aluminum hydride should be handled under an inert atmosphere.) The mixture is stirred at room temperature for 12 h. The following procedure is carried out under air. Theflask is taken into awell-ventilated fumehood, and a tube is connected from the three-way stopcock to a solvent trap, which is also connected via another tube to an Erlenmeyer flask containing a dilute aqueous NaOH solution. A mixture of distilled water and THF (1:1 v/v, 50 mL) is added dropwise to the flask via pipette. (Caution: Residual LiAlH4 reacts vigorously with water.) After completing the gas evolution, distilled water (200 mL) is added, and then conc. HCl (300 mL) is carefully added with stirring. The reaction mixture is filtered, and the resultant solution is concentrated with rotary evaporator to remove most of THF. The product is extracted with CH2Cl2 (5  100 mL) and separated from the aqueous layer. After being dried over MgSO4, the solution is evaporated until dryness. The compound is crystallized from ethyl acetate (150 mL) to give colorless crystals. Yield: 11.0 g (45%). H NMR (CDCl3):10 d 7.22 (t, J ¼ 7.6 Hz, 1H), 7.02 (d, J ¼ 7.6 Hz, 2H), 6.97 (s, 4H), 3.01 (s, 1H), 2.33 (s, 6H), 2.01 (s, 12H). mp 211–214 C.

1

C. Fe[SC6H3-2,6-(MESITYL)2]2 (MESITYL ¼ C6H2-2,4,6-Me3) Fe½NðSiMe3 Þ2 Š2 þ 2 HSC6 H3 -2; 6-ðmesitylÞ2 ! Fe½SC6 H3 -2; 6-ðmesitylÞ2 Š2 þ 2 HNðSiMe3 Þ2 Procedure This compound is reported by Power and coworkers.10 In a glovebox, a toluene (5 mL) solution of Fe[N(SiMe3)2]2 (0.380 g, 1.01 mmol) is charged into a Schlenk tube. Also in the glovebox, HSC6H3-2,6-(mesityl)2 (0.700 g, 2.76 mmol) is dissolved in toluene (5 mL) and hexane (10 mL), and this solution is added to the iron(II) bisamide solution using a pipette. The reaction proceeds smoothly with the formation of a red suspension. The Schlenk tube is taken out from the glovebox, and then the

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solution is stirred for 15 min at room temperature. The mixture is heated at 70 C to lead to a homogeneous solution, and then the Schlenk tube is left standing at room temperature. Within 1 day, red crystals of product precipitate from the solution. The Schlenk tube is taken into a glovebox, and the crystals are collected by filtration. Yield: 0.370 g (49%). 1

H NMR (600 MHz, C6D6, 297K): d 49.8 (4H, m-C6H3), 42.2 (12H, p-mesityl), 7.0 (24H, o-mesityl), 22.4 (8H, m-mesityl), 24.8 (2H, p-C6H3). UV–vis (cyclohexane, (e, M 1 cm 1)): 287 (sh, 2300) nm. mp 270–272 C.

Properties The product is an extremely air- and moisture-sensitive red solid that can be stored for months in the absence of air and moisture.10 It is soluble in aromatic hydrocarbons. 1 H NMR (toluene-d8) and infrared spectrum have been described.10 Related Compounds Using only 1 equiv of the thiol affords the monothiolate-monoamide {Fe[SC6H3 2,6-(mesityl)2]{N(SiMe3)2}. 2,6-Di(xylyl)benzenethiol, which was reported by Luening and Baumgartner,12 gives analogous complex Fe[SC6H3-2,6-(xylyl)2]2, which is less soluble than the mesityl derivative.131 H NMR (600 MHz, C6D6, 297K): d 49.2 (4H, m-C6H3 or p-xylyl), 6.7 (24H, –CH3), 22.2 (8H, m-xylyl), 26.1 (2H þ 4H, p-C6H3 and m-C6H3 or p-xylyl). UV–vis (cyclohexane, lmax, nm (e, M 1 cm 1)): 452 (300), 395 (300), 287 (sh, 750). meff (Evans method, 297K): 5.1 mB. Anal. Calcd. for C44H42FeS2: C, 76.50; H, 6.13; S, 9.28. Found: C, 76.57; H, 5.91; S, 9.41. mp 295–297 C. References 1. 2. 3. 4.



1

R. H. Holm, Acc. Chem. Res. 10, 427–434 (1977). P. V. Rao and R. H. Holm, Chem. Rev. 104, 527–560 (2004). Y. Ohki, Y. Ikagawa, and K. Tatsumi, J. Am. Chem. Soc. 129, 10457–10465 (2007). R. Hauptmann, R. Klib J. Schneider, and G. Henkel, Z. Anorg. Allg. Chem. 624, 1927–1936 (1998).

H NMR (C6D6): d 7.10 (t, J ¼ 7.4 Hz, 2H), 7.04 (d, J ¼ 7.4 Hz, 4H), 6.96 (t, J ¼ 7.6 Hz, 1H), 6.81 (d, J ¼ 7.6 Hz, 2H), 3.06 (s, 1H), 2.08 (s, 12H). 1 H NMR (CDCl3): d 7.25 (obscured CDCl3, 1H), 7.20 (t, J ¼ 7.6 Hz, 2H), 7.14 (d, J ¼ 7.6 Hz, 4H), 7.04 (d, J ¼ 7.6 Hz, 2H), 2.96 (s, 1H), 2.05 (s, 12H). mp 114–116 C.

34. (1,3-Propanedithiolato)-Hexacarbonyldiiron and Cyanide Derivatives

143

5. R. A. Andersen, K. Faegri Jr., J. C. Green, A. Haaland, M. F. Lappert, W.-P. Leung, and K. Rypdal, Inorg. Chem. 27, 1782–1786 (1988) 6. A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen, and F. J. Timmers, Organometallics 15, 1518–1520 (1996). 7. E. H. Amonoo-Neizer, R. A. Shaw, D. O. Skovlin, and B. C. Smith, Inorg. Synth. 8, 19–22 (1966). 8. M. M. Olmstead, P. P. Power, and S. C. Shoner, Inorg. Chem. 30, 2547–2551 (1991). 9. D. J. Evans, D. L. Hughes, and J. Silver, Inorg. Chem. 36, 747–748 (1997). 10. J. J. Ellison, K. Ruhlandt-Senge, and P. P. Power, Angew. Chem., Int. Ed. Engl. 33, 1178–1180 (1994). 11. A. Saednya and H. Hart, Synthesis 1455–1458 (1996). 12. U. Luening and H. Baumgartner, Synlett 8, 571–572 (1993). 13. S. Ohta, Y. Ohki, Y. Ikagawa, R. Suizu, and K. Tatsumi, J. Organomet. Chem. 692, 4792–4799 (2007).

34. (1,3-PROPANEDITHIOLATO)-HEXACARBONYLDIIRON AND CYANIDE DERIVATIVES Submitted by AMANDA E. MACK* and THOMAS B. RAUCHFUSS* Checked by KOSHI OHNISHI,† YASUHIRO OHKI,† and KAZUYUKI TATSUMI†

Dithiolatodiiron hexacarbonyl complexes were first reported by Reihlen and then Hieber and are generally prepared from the reaction of thiols with iron carbonyls.1 Fe2(S2CnH2n)(CO)6 derived from ethanedithiol (n ¼ 2) and 1,3propanedithiol (n ¼ 3) were prepared by Huttner and coworkers by the reaction of Fe3(CO)12 with the respective dithiols.2 Lotz prepared the propanedithiolatex from Fe(CO)5 and 1,3-dithiane (S2(CH2)3).3 Extensive work has been reported for the related methanethiolates Fe2(SCH3)2(CO)6, which exist in solution as two isomers, depending on the relative orientation of the methyl groups.4 The ethanedithiolate is more amenable to analysis because it exists exclusively as a single isomer of C2v symmetry. The propanedithiolate is structurally more complex owing to the folded conformation of the Fe2S2C3 core.2 In solution, the two conformers rapidly interconvert.

*

Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801 † Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan

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The hexacarbonyls Fe2(S2CnH2n)(CO)6 readily undergo substitution by cyanide,5,6 phosphines,7 isocyanides,8N-heterocyclic carbenes,9 and other donor ligands. With monodentate ligands, disubstitution proceeds efficiently to afford derivatives Fe2(S2CnH2n)(CO)4L2 (L ¼ RNC, NHC) and, for cyanide, [Fe2(S2CnH2n) (CO)4(CN)2]2 .10 Monosubstitution can be complicated by competitive disubstitution reactions, but this problem can be circumvented by in situ generation of the labile acetonitrile complex, which undergoes rapid monosubstitution as illustrated in a procedure given below.10 In contrast to the parent hexacarbonyls, substituted derivatives undergo many electrophilic reactions, including protonation to afford hydrides. The hydrides are efficient catalysts for hydrogen evolution.11 & Caution. and skin.

Dithiols are malodorous as well as irritants to the eyes

A. (1,3-PROPANEDITHIOLATO)HEXACARBONYLDIIRON 2 Fe3 ðCOÞ12 þ 6 C3 H6 ðSHÞ2 ! 3 Fe2 ðS2 C3 H6 ÞðCOÞ6 þ 3 H2 þ 6 CO Procedure A 250-mL round-bottomed Schlenk flask containing a Teflon-covered magnetic stirring bar is charged with benzene (20 mL). The benzene is sparged with nitrogen for a few minutes and then 1,3 propanedithiol (0.79 mL, 7.95 mmol) and solid Fe3(CO)12 (3.2 g, 6.36 mmol) are added. The flask is fitted with a reflux condenser, and the mixture is heated at vigorous reflux under nitrogen for 1.5–2 h. During the reaction, the solution changes the color from green to red. The reaction solution was allowed to cool to room temperature, and the contents were evaporated to an oily red solid. The solid is dissolved in 5 mL of hexane and chromatographed on a 40 cm  2 cm column, eluting with hexanes. The main band, which is red, is collected and evaporated to dryness, leaving red-orange crystals. The yield is 2.26 g (92%).* *

The checkers used a 1.5-h reflux time to give a 69% yield

34. (1,3-Propanedithiolato)-Hexacarbonyldiiron and Cyanide Derivatives

145

Anal. Calcd. for C9H6Fe2O6S2: C, 28.00; H, 1.55; N, 0.00. Found: C, 28.03; H, 1.37; N, 0.12. IR (hexanes): 2076, 2035, 2006, 1993, 1982 cm 1. 1 H NMR (acetone-d6): d 2.26 (t, 4H), 1.86 (m, 2H). Properties The product is air stable for extended periods. It is soluble in a variety of organic solvents. The product is best characterized by its infrared spectrum. The same procedure can be used to prepare ethanedithiolate. IR (hexanes): 2077, 2037, 2007,1995, 1984 cm 1. 1 H NMR (CDCl3): d 2.38 (s, 4H). B. TETRAETHYLAMMONIUM (1,3-PROPANEDITHIOLATO) TETRACARBONYLDIIRON DICYANIDE Fe2 ðS2 C3 H6 ÞðCOÞ6 þ 2NEt4 CN !ðNEt4 Þ2 ½Fe2 ðS2 C3 H6 ÞðCNÞ2 ðCOÞ4 Š þ 2CO Procedure A 100-mL round-bottomed Schlenk flask containing a magnetic stirring bar is charged with Fe2(S2C3H6)(CO)6 (0.56 g, 1.45 mmol, 1 equiv) and MeCN (20 mL). The red-orange solution is treated with a solution of NEt4CN (0.45 g, 2.9 mmol) in 10 mL acetonitrile and stirred for 1 h. The resulting dark red solution was evaporated to dryness, and the remaining red solid was washed with 3  5 mL hexanes and dried in vacuum. The yield is 0.86 g (95%). Anal. Calcd. for C24H46Fe2N4O4S2: C, 45.72; H, 7.35; N, 8.89; S, 10.17; Fe, 17.72. Found: C, 45.97; H, 7.33; N, 8.98; S, 10.34; Fe, 17.59. 1 H NMR (CD3CN): d 1.21 (t, 24H, NCH2CH3), 1.67 (m, 2H, CH2CH2CH2), 1.85 (t, 4H, SCH2), 3.18 (q, 16H, NCH2CH3). IR (MeCN): 2072, 2036, 1961, 1913, 1879 cm 1. Properties The compound is soluble in water, methanol, and acetonitrile. Both the solid and especially its solutions are unstable in air. (NEt4)2[Fe2(S2C3H6)(CN)2(CO)4] is unreactive toward other ligands, including cyanide. It has been characterized crystallographically.5 The reaction of the ethanedithiolate Fe2(S2C2H4)(CO)6 with NEt4CN under the same conditions afforded (NEt4)2[Fe2(S2C3H6)(CN)2(CO)4]. 1 H NMR (CD3OD): d 3.28 (q, 16H, NCH2CH3), 1.96 (s, 4H, SCH2), 1.21 (t, 24H, NCH2CH3). IR (MeCN): 2078, 2029, 1961, 1917, 1880 cm 1.

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C. TETRAETHYLAMMONIUM (1,3-PROPANEDITHIOLATO) PENTACARBONYLDIIRON CYANIDE Fe2 ðS2 C3 H6 ÞðCOÞ6 þ Me3 NO þ MeCN ! Fe2 ðS2 C3 H6 ÞðCOÞ5 ðMeCNÞ þ NMe3 þ CO2 Fe2 ðS2 C3 H6 ÞðCOÞ5 ðMeCNÞ þ NEt4 CN ! NEt4 ½Fe2 ðS2 C3 H6 ÞðCNÞðCOÞ5 Š þ MeCN Procedure A solution of 0.25 g (0.65 mmol) of Fe2(S2C3H6)(CO)6 in 10 mL of MeCN is treated with a solution of 0.049 g (0.65 mmol) of Me3NO in 10 mL of MeCN. The infrared spectrum of the resulting dark brown solution indicates formation of the acetonitrile adduct [IR(MeCN): nCO ¼ 2050, 2040, 1990, 1962, 1932 cm 1]. The dark brown solution is then cooled to 40 C and is treated with a solution of 0.10 g (0.65 mmol) of NEt4CN in 10 mL of MeCN. The solution changes to dark red within minutes. The cooling bath is removed and the reaction mixture is allowed to warm to room temperature. The dark red solution is evaporated to dryness under vacuum. The resulting red oil is extracted into 10 mL of THF, and this extract is filtered. The filtrate is reduced to approximately 1 mL, and the product is precipitated upon addition of 20 mL of hexanes and washed with additional hexanes to leave an oily residue. The crude red product is dried under vacuum for 1 h, leaving a red solid. Yield: 0.29 g (87%). Anal. Calcd. for C17H26Fe2N2O5S2: C, 39.71; H, 5.10; N, 5.45; S, 12.47. Found: C, 39.43; H, 5.06; N, 5.43; S, 12.47. IR (THF): nCN ¼ 2091; nCO ¼ 2030, 1975, 1955, 1941, 1914 cm 1. 1 H NMR (CD3CN): d 3.16 (q, 8H, NCH2CH3), 2.18 and 1.77 (br, 6H, S(CH2)3S), 1.19 (t, 12H,NCH2CH3).

Properties The compound is soluble in water, methanol, and acetonitrile. Both the solid and especially its solutions are unstable in air. The product is most easily obtained as a glassy solid, but single crystals can be obtained by recrystallization from THF–hexanes. The salt has been characterized crystallographically.10 The acetonitrile complex is stable for minutes in acetonitrile solution. It undergoes substitution by a variety of ligands under mild conditions.10

34. (1,3-Propanedithiolato)-Hexacarbonyldiiron and Cyanide Derivatives

147

References 1. (a) H. Reihlen, A. Gruhl, and G. v. Hessling, J. Liebigs Ann. Chem. 472, 268–287 (1929). (b) W. Hieber and P. Spacu, Z. Anorg. Allg. Chem. 233, 852–864 (1937). 2. A. Winter, L. Zsolnai, and G. Huttner, Z. Naturforsch. 37b, 1430–1436 (1982). 3. S. Lotz, P. H. van Rooyan, and M. M. Dyk, Organometallics 6, 499–505 (1987). 4. (a) K. Fauvel, R. Mathieu, and R. Poilblanc, Inorg. Chem. 15, 976–978 (1976). (b) J. J. Bonnet, R. Mathieu, R. Poilblanc, and J. A. Ibers, J. Am. Chem. Soc. 101, 7487–7496 (1979). 5. M. Schmidt, S. M. Contakes, and T. B. Rauchfuss, J. Am. Chem. Soc. 121, 9736–9737 (1999). 6. (a) E. J. Lyon, I. P. Georgakaki, J. H. Reibenspies, and M. Y. Darensbourg, Angew. Chem., Int. Ed. 38, 3178–3180 (1999). (b) A. Le Cloirec, S. C. Davies, D. J. Evans, D. L. Hughes, C. J. Pickett, S. P. Best, and S. Borg, Chem Commun. 2285–2286 (1999). ˚ kermark, and L. Sun, Eur. J. Inorg. Chem. 7. P. Li, M. Wang, C. He, G. Li, X. Liu, C. Chen, B. A 2506–2513 (2005). 8. (a) J. L. Nehring and D. M. Heinekey, Inorg. Chem. 42, 4288–4292 (2003). (b) C. A. Boyke, T. B. Rauchfuss, S. R. Wilson, M.-M. Rohmer, and M. Benard, J. Am. Chem. Soc. 126, 15151–15160 (2004). 9. (a) J.-F. Capon, S. El Hassnaoui, F. Gloaguen, P. Schollhammer, and J. Talarmin, Organometallics 24, 2020–2022 (2005). (b) J. W. Tye, J. Lee, H. W. Wang, R. Mejia-Rodriguez, J. H. Reibenspies, M. B. Hall, and M. Y. Darensbourg, Inorg. Chem. 44, 5550–5552 (2005). 10. F. Gloaguen, J. D. Lawrence, M. Schmidt, S. R. Wilson, and T. B. Rauchfuss, J. Am. Chem. Soc. 123, 12518–12527 (2001). 11. F. Gloaguen, J. D. Lawrence, and T. B. Rauchfuss, J. Am. Chem. Soc. 123, 9476–9477 (2001).

Chapter Eight

RUTHENIUM COMPLEXES 35. RUTHENIUM(II)-CHLORIDO COMPLEXES OF DIMETHYLSULFOXIDE Submitted by IOANNIS BRATSOS* and ENZO ALESSIO* Checked by MARK E. RINGENBERG† and THOMAS B. RAUCHFUSS†

The two ruthenium(II)-chlorido-dimethylsulfoxide (dmso) complexes cis- and trans-[RuCl2(dmso)4], and in particular the cis isomer, have a rich chemistry and are widely used as precursors in inorganic synthesis.1 Depending on the conditions, both the dmso and the chlorido ligands can be selectively replaced by mono- or polydentate ligands. The preparation of cis-[RuCl2(dmso)4] was first reported in 1971 by James et al., by treatment of hydrated RuCl3 with H2 in warm dimethylsulfoxide (DMSO).2 This procedure is however inconvenient for routine syntheses. Two years later, Wilkinson and coworkers reported an improved and simpler synthetic procedure for cis-[RuCl2(dmso)4], in which hydrated RuCl3 was simply refluxed in DMSO for 5 min and the product was eventually precipitated by addition of acetone after concentration.3 In 1975, the geometry of the complex was unambiguously established as cis by X-ray crystallography.4 The complex can be more correctly formulated as cis,fac[RuCl2(dmso-S)3(dmso-O)], since three of the sulfoxide ligands are bound in *

Dipartimento di Scienze Chimiche, Universita di Trieste, 34127 Trieste, Italy. Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

†

Inorganic Syntheses, Volume 35, edited by Thomas B. Rauchfuss Copyright Ó 2010 John Wiley & Sons, Inc.

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facial geometry through sulfur (dmso-S), while the fourth and most labile is bound through oxygen (dmso-O). Despite the wide use of cis-[RuCl2(dmso)4] as Ru(II) precursor, its apparently simple and straightforward synthetic procedure can be problematic, possibly because the reaction mechanism is largely unknown, the nature of hydrated RuCl3 is uncertain and depends on the commercial source (even though it is typically formulated as RuCl33H2O, it is actually a mixture of Ru(III) and Ru(IV) species and the number of water molecules is variable), and the DMSO solvent can contain variable amounts of impurities (in primis water and dimethylsulfide). The influence of these factors in the successful synthesis remains, to date, unclear but definitely they contribute to the variability of Wilkinson’s procedure. On the other hand, the synthetic procedures leading to the trans isomer (in which all four sulfoxides are bound through sulfur) are uncontested. Our group reported first, in 1988, the synthesis of trans-[RuCl2(dmso-S)4] by photochemical isomerization of the cis isomer in DMSO solution at room temperature and established its structure by X-ray analysis.5 The same compound was also obtained by electrochemical reduction of the Ru(III) intermediate hydrogen trans-bis(dimethylsulfoxide)tetrachloridoruthenate(III) ([(dmso)2H]trans[Ru(dmso-S)2Cl4]).6 In 1990, James and coworkers reported a third alternative synthesis of trans-[RuCl2(dmso-S)4], by treatment of hydrated RuCl3 in DMSO at 70 C.7 The last two preparations established that the trans complex is a kinetic intermediate in the reduction of hydrated RuCl3 in DMSO to the thermodynamically most stable cis isomer (trans to cis isomerization occurs quantitatively in warm DMSO).

DMSO RuCl3 xH2O

heat

SMe2 Me2 O Cl S O Ru Me2S Cl O S O Me2 cis-[RuCl2(dmso)4]

hv heat

2 O Me S O SMe2 Cl Ru Me2S Cl O S O Me 2

trans-[RuCl2(dmso-S)4]

Herein, we present an improved, convenient, and highly reproducible synthesis of cis-[RuCl2(dmso)4], as well as the routine synthesis of the trans isomer, trans-[RuCl2(dmso-S)4]. The first procedure is a modified and improved version of that given in the literature.3 It involves a preliminary, but essential, step: the reflux of commercial hydrated RuCl3 in ethanol. This procedure, compared to that originally established by Wilkinson and coworkers, besides being well reproducible, also avoids the tedious concentration of the hot DMSO solution.

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A. cis-DICHLORIDOTETRAKIS(DIMETHYLSULFOXIDE) RUTHENIUM(II) Procedure A 100-mL round-bottomed flask equipped with a condenser and a magnetic stirring bar is charged with RuCl3xH2O (2.00 g, 7.65 mmol assuming x ¼ 3) partially dissolved in ethanol (50 mL). The stirred mixture is heated to reflux for 3 h, during which time the starting material dissolves completely, and the color of the solution changes from brown to deep green. Ethanol is removed with rotary evaporator (filtration on paper should be performed prior to concentration if undissolved black material is found at the bottom of the flask). The remaining dark green oily residue is dissolved in DMSO (8 mL) in a 100-mL round-bottomed flask. The flask is connected to a condenser, and the mixture is placed in an oil bath preheated at 150 C and magnetically stirred for 2 h. Within the first minutes, the solution becomes more fluid and its color changes from green to bright orange (typical of Ru (III)-chlorido-dmso intermediates). After 1 h, formation of the product as a yellow solid is observed. After cooling to room temperature, more product precipitates. The formation of the bright yellow microcrystalline solid is completed by addition of acetone (60 mL). After allowing the slurry to stand at room temperature for 1 day, the product is collected by filtration, thoroughly washed with acetone (3  5 mL), and dried in vacuum. Yield: 2.77 g (5.72 mmol, 75%). 1

H NMR (D2O): d 3.46 (dmso-S), 3.44 (dmso-S), 3.32 (dmso-S), 2.80 (dmso-O). IR (KBr, nSO): 1122, 1110, and 1095 (dmso-S), 921 cm 1 (dmso-O).

Properties The product is light, air, and moisture stable for very long periods of time at room temperature. It is well soluble in water, nitromethane, chloroform, and dichloromethane, and partially soluble in methanol and DMSO. In aqueous solution, this compound releases within minutes the O-bonded dmso. Thus, even when recorded immediately after dissolution, the 1 H NMR spectrum in D2O displays, in addition to the signals of the parent compound, three new intense singlets in the dmso-S region (d ¼ 3.49, 3.47, 3.39) for the aqua species cis,fac-[RuCl2(dmso-S)3(H2O)], together with the resonance of free dmso (d ¼ 2.71). The singlets of the parent compound disappear within minutes and the spectrum of the resulting aqua species changes very slowly (hours) due to the dissociation of one chlorido ligand. Partial hydrolysis also occurs in commercial CDCl3 and CD2Cl2 and the corresponding NMR spectra are always the sum of those of the parent compound (equally intense singlets at d ¼ 3.50, 3.43, 3.33 for dmso-S, and at d ¼ 2.73 for dmso-O) and of the aqua species (equally intense singlets at d ¼ 3.53, 3.47, 3.41 for dmso-S, and at

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d ¼ 2.62 for free dmso). The extent of the hydrolysis depends on the concentration of the complex and on the content of adventitious water. This feature is often confusing, and wrongly suggests the presence of by-products in the original sample. Solid-state IR spectroscopy is highly diagnostic for establishing the binding mode of dmso through the frequency of the SO stretching mode: nSO for dmso-S is higher (range 1080–1150 cm 1), and for dmso-O is lower (range 890–950 cm 1), compared to that of the free ligand at 1055 cm 1. Thus, the IR spectrum of cis-[RuCl2(dmso)4] (see above) presents strong SO stretching bands in both ranges (however, in the solid state, their number and frequencies depend slightly upon the conformations of the coordinated sulfoxides).5 B. trans-DICHLORIDOTETRAKIS(DIMETHYLSULFOXIDE) RUTHENIUM(II) Procedure A 100-mL round-bottomed flask equipped with a condenser and a magnetic stirring bar is charged with cis-[RuCl2(dmso)4] (2.50 g, 5.16 mmol) suspended in DMSO (40 mL). The mixture is stirred and warmed to 80 C until complete dissolution of the yellow solid (ca. 30 min). The yellow solution is transferred into a water-cooled photoreactor equipped with 125-W mercury lamp and is irradiated for 4 h. During this time, the temperature is maintained at ca. 25 C. The same reaction can also be performed under direct sunlight, but requires typically at least 6 h. The deep yellow microcrystalline precipitate is filtered, washed with DMSO (2 mL) and acetone (3  5 mL), and vacuum dried at room temperature. Yield: 2.00 g (4.13 mmol, 80%). Properties The compound is deep yellow solid, which is light, air, and moisture stable for long periods of time at room temperature. It is, like the cis isomer, soluble in water but dissolution takes a few minutes. It is also soluble in nitromethane, chloroform, and dichloromethane, but considerably less soluble in DMSO. It is very labile in aqueous solution. The 1 H NMR spectrum in D2O displays two equally intense singlets at d 3.35 (dmso-S) and 2.71 (free dmso). The downfield resonance is assigned to the equivalent S-bonded sulfoxides in the diaqua species trans,cis,cis[RuCl2(dmso-S)2(H2O)2], which forms from the parent compound immediately after dissolution upon release of two adjacent dimethylsulfoxide molecules. In CDCl3, the 1 H NMR spectrum shows two singlets in 3:1 ratio at d 3.41 (dmso-S) and 2.62 (free dmso), consistent with the dissociation of only one dmso-S and formation of a symmetrical five-coordinate RuCl2(dmso-S)3 species. The solid-state IR spectrum is simpler than that of the cis isomer and shows a single SO stretching band at 1080 cm 1 for the four equivalent dmso-S ligands.

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References E. Alessio, Chem. Rev. 104, 4203 (2004). B. R. James, E. Ochiai, and G.I. Rempel, Inorg. Nucl. Chem. Lett. 7, 781 (1971). I. P. Evans, A. Spencer, and G. Wilkinson, J. Chem. Soc., Dalton Trans. 204 (1973). A. Mercer and J. Trotter, J. Chem. Soc., Dalton Trans. 2480 (1975). E. Alessio, G. Mestroni, G. Nardin, W. M. Attia, M. Calligaris, G. Sava, and S. Zorzet, Inorg. Chem. 27, 4099 (1988). 6. E. Alessio, G. Balducci, M. Calligaris, G. Costa, W. M. Attia, and G. Mestroni, Inorg. Chem. 30, 609 (1991). 7. J. S. Jaswal, S. J. Rettig, and B. R. James, Can. J. Chem. 68, 1808 (1990).

1. 2. 3. 4. 5.

36. SYNTHESIS OF CHLORIDE-FREE RUTHENIUM(II) HEXAAQUA TOSYLATE, [Ru(H2O)6]tos2 ´ BOR LAURENCZY* Submitted by CE´LINE FELLAY* and GA † Checked by STEVEN M. BISCHOF and ROY A. PERIANA†

The general starting material for the synthesis of water-soluble Ru compounds is the commercially available RuCl3xH2O, but many organometallic processes and fundamental kinetic studies and its equilibrium behavior require halogen-free Ru(II) complexes, such as [Ru(H2O)6]2þ.1 The complex [Ru(H2O)6]2 þ has only water in the first coordination sphere, with weakly coordinating anions such as p-toluenesulfonate (tos). Furthermore, [Ru(H2O)6]tos2 can be used as specific ‘‘source’’ to synthesize Ru catalysts where a high yield and a halogen-free compound are needed. Here, we report the modified synthesis2 of the [Ru(H2O)6]tos2 complex. The synthesis entails reduction of RuO4 with Pb, which is chosen for its mild redox potential. Although an excess is used, most of the Pb is removed/reused. The small amount of Pb2 þ generated in this reaction is precipitated as the very sparingly soluble PbSO4 (Ks ¼ 1.82  10 8 M2). Thus, the use of Pb does not present major disposal issue. General Remarks All manipulations are performed under argon atmosphere using standard Schlenk techniques. All solutions are degassed with argon prior to use.

*

Institut des Sciences et Ingenierie Chimiques, Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland. † The Scripps Energy Laboratories, The Scripps Research Institute, Jupiter, FL 33458.

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& Caution RuO4 is a toxic gas; therefore, the setup should be placed in a well-ventilated fume hood. Procedure (a) Synthesis of RuO2. 3.0 g (ca. 12 mmol) RuCl3xH2O (Johnson Matthey, 40–43% ruthenium, x  2) is added to a solution of 24.6 g NaOH (0.6 mol) dissolved in 123 mL H2O. The reaction mixture is then heated to 60 C for 30 min and stirred overnight at room temperature. The black product is collected by filtration, washed with H2O until the filtrate is chloride free (negative AgNO3 test), and dried in air. Yield: 2.1 g of the oxide containing some chloride and water. (b) Preparation of [Ru(H2O)6]tos2.

RuO2

NaIO4 H2 SO4

! RuO4

Pb H2 SiF6

! ½RuðH2 OÞ6 Š2 þ

ion exchange

! ½RuðH2 OÞ6 ŠðtosÞ2

Prepare the following four solutions: Solution A: 10.5 g (0.049 mol) NaIO4 in H2O (85 mL). Solution B: 20 g Pb (ca. 0.1 mol, approx. particle diameter is 0.5 mm), previously activated by stirring in 28 mL 50% HNO3,* in a 1 M solution of H2SiF6 (140 mL). Solution C: 3 g Pb (ca. 15 mmol), previously activated in 4.3 mL of 50% HNO3, in 30 mL H2SiF6 1 M. Solution D: ice-cold 50% H2SO4 solution (42 mL).

The first three solutions are placed in the setup described in Fig. 1, except for solution D. Solutions A and B are magnetically stirred, and A is placed in an ice bath. The whole setup is degassed with argon during 1 h. The sulfuric acid solution D is degassed separately. The dropping funnel is filled with this solution. The flow of argon is maintained at a slow rate, a few bubbles per second. Then, the 2.1 g RuO2 is added to A and dropwise addition of H2SO4 into A is started, while maintaining the argon stream. The addition requires about 30 min.

*

Pb is stirred for 15 min in HNO3 50%, filtered, washed with water until neutrality, and used immediately.

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Figure 1. Apparatus for generation and reduction of RuO4. The apparatus consists of a 500-mL three-necked flask (A), a 500-mL two-necked flask (B), a 250-mL bubbler (C), and a 100-mL dropping funnel (D). Joints were sealed with parafilm, no grease was used, and interconnections between flasks were made with plastic tubing. Before addition of the solution, the whole setup is placed under vacuum to check for leaks. The distance between A and B should be as short as possible. The entire apparatus is protected from light (the fume hood window was carefully covered by black paper).

Once the addition of solution D is complete, the ice bath is removed from A, and the reaction mixture is allowed to reach room temperature. Stirring is continued for 2 days under an argon stream and in the dark. After 2 days, solution A is black, indicating an incomplete reaction. B is dark red indicative of product. To flask B is added Pb (5 g, ca. 15 mmol), activated in 7 mL of 50% HNO3. To flask A is added NaIO4 (1.26 g, 0.006 mol). Flask A is then heated at 40 C for 1 day. Although solution A remains black, solution B is filtered under argon. H2SO4 2 M (42 mL, degassed with argon) is added to the filtrate to precipitate PbSO4, the solution is stirred for 30 min, decanted for 15 min, and filtered. A 30-mm diameter chromatography column is charged with a Dowex 50 H þ resin (40 g). The resin is first washed with degassed H2O. Then, the solution containing [Ru(H2O)6]2 þ is added dropwise using a dropping funnel. A purple band is formed on top of the column. The column is then washed with H2O (125 mL), with a 0.1 M tosylic acid (Htos) solution (300 mL),* and then with 1.2 M

*

The checkers observed a reddish band when eluting with the dilute Htos solution. The band was discarded.

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Htos (300 mL). The purple band is eluted with the 1.2 M Htos solution. The band is collected and concentrated under vacuum at 40 C until precipitation occurs (ca. 120 mL), which requires ca. 9 h. The solution is left overnight at 0 C to allow for more complete precipitation. The solution is then filtered under argon, and the pink fluffy needles are washed with degassed ethyl acetate (2  20 mL) and then diethyl ether (2  20 mL) and dried in vacuo. The filtrate is concentrated at 40 C, and a second fraction is obtained and worked up. Yield (two fractions): 3.3 g (50%, based on RuCl3xH2O). The apparatus was cleaned as usual, and the ruthenium deposit traces were eliminated by a 5% sodium hypochlorite solution. Anal. Calcd. for C14H26O12S2Ru: C, 30.5; H, 4.7. Found: C, 31.0; H, 4.8. UV–vis: 534 and 394 nm with the molar absorbances e ¼ 12 M 1 cm 1 and 15 M 1 cm 1, respectively (no traces could be detected of Ru3 þ at 390 nm, e ¼ 30 M 1 cm 1). The concentrated aqueous solution gives a singlet signal in the 17 O NMR spectrum at 196 ppm from the reference water resonance at 0 ppm (no other signals could be detected in the region from þ 50 to 200 ppm, no traces of [Ru(H2O)6]3 þ were detected at þ 35 ppm).3 Properties [Ru(H2O)6](tos)2 is a pink solid with a high solubility in water. It is soluble in dmso, but insoluble in diethyl ether. The resulting aqueous solution of [Ru(H2O)6]2 þ is readily oxidized to yellow [Ru(H2O)6]3 þ . [Ru(H2O)6](tos)2 was successfully used for kinetic studies,4 synthesis,5 and catalysis.6 Acknowledgments We thank the Swiss National Science Foundation and EPFL for financial support. References 1. M. Loy and G. Laurenczy, Helv. Chim. Acta 88, 557 (2005). 2. (a) P. Bernhard, H. B. B€urgi, J. Hauser, H. Lehmann, and A. Ludi, Inorg. Chem. 21, 3936 (1982). (b) P. Bernhard, M. Biner, and A. Ludi, Polyhedron 9, 1095 (1990). 3. N. Aebischer, G. Laurenczy, A. Ludi, and A. E. Merbach, Inorg. Chem. 32, 2810 (1993). 4. (a) P. V. Grundler, G. Laurenczy, and A. E. Merbach, Helv. Chim. Acta 84, 2854 (2001). (b) G. Laurenczy, F. Joo´, and L. Nadasdi, Inorg. Chem. 39, 5083 (2000). 5. (a) G. Laurenczy, L. Helm, A. Ludi, and A. E. Merbach, Inorg. Chim. Acta 189, 131 (1991). (b) G. Laurenczy and A. E. Merbach, Chem. Commun. 187 (1993). 6. C. Fellay, P. J. Dyson, and G. Laurenczy, Angew. Chem., Int. Ed. 47, 3966 (2008).

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37. BASIC RUTHENIUM ACETATE AND MIXED VALENCE DERIVATIVES Submitted by JOHN C. GOELTZ,* STARLA D. GLOVER,* JAMES HAUK,* and CLIFFORD P. KUBIAK* Checked by ROSS D. PUTMAN† and THOMAS B. RAUCHFUSS†

Oxo-centered triruthenium clusters have been the subject of considerable study because of their extensive redox chemistry.1–9 The triruthenium clusters with a carbonyl ligand are particularly interesting because infrared lineshape analysis of the n(CO) bands in various oxidation states illuminates previously unknown details of rates of very fast intramolecular electron transfer.10–14 The [Ru3(m3-O) (m-OAc)6L3] þ unit is a versatile building block for extended structures because each metal center has a single exchangeable coordination site (Fig. 1). Unlike the corresponding oxo-centered iron triangles,15 ligands coordinated to the three exchangeable external sites of the Ru3 clusters are typically not labile when the ligands are pyridines, isocyanides, NO (for RuIII), or CO (for RuII), allowing for facile preparation and purification of variously substituted mixed ligand complexes. Here, we report the synthesis of the Ru3III,III,III cationic oxo-centered cluster with three aquo ligands, the facile reduction of the cluster to a neutral Ru3III,III,II core with either aquo or pyridyl ligands, and introduction of a single carbon monoxide at the formally RuII site. The latter molecule with one carbonyl and two semilabile aquo ligands is a very stable and versatile starting material, and its use in preparing many new complexes is limited only by creativity in bridging and terminal ligand substitution.7,16,17 A. TRI(AQUO)-m3-OXO-HEXAKIS(m-ACETATE)TRIRUTHENIUM ACETATE, [Ru3(m3-O)(m-OAc)6(H2O)3]OAc 3 RuCl3 ðH3 OÞ3 þ 9 NaOAc ! ½Ru3 ðm3 -OÞðm-OAcÞ6 ðH2 OÞ3 Š½OAcŠ þ 2 HOAc þ 9 NaCl þ 5 H2 O Procedure A 500-mL round-bottomed flask is charged with RuCl33H2O (6 g, 22.9 mmol), NaOAc3H2O (12 g, 88.2 mmol), a stir bar, 150 mL absolute ethanol, and 150 mL

*

Department of Chemistry and Biochemistry, University of California at San Diego, San Diego, CA92093. Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

†

37. Basic Ruthenium Acetate and Mixed Valence Derivatives

157

L

O

O

Ru

O

O O

OO

Ru

Ru L

O

O

O

O

O

L

O

Figure 1. Structure of basic ruthenium acetate framework.

glacial acetic acid. The brown solution is refluxed for 4 h, during which time the color changes to deep forest green. The reaction is cooled to room temperature, and filtered through filter paper, discarding the insoluble materials. The solvent is removed from the filtrate in vacuo. The resulting oily residue is taken up in a minimum of methanol (ca. 25 mL) and precipitated with an excess of acetone (ca. 500 mL). The resulting green powder is collected on a glass frit and washed with 3  30 mL acetone and 1  30 mL diethyl ether. Yield: 9 g. A single recrystallization does not remove all of the sodium acetate, but the product is sufficiently pure for syntheses in parts B and C. High-purity samples are obtained by dissolving the green powder in a minimum amount (ca. 100 mg in 10 mL) of premixed 1:1 methanol/acetone, cooling to 40 C (MeCN/dry-ice bath), and collecting the precipitate from the cold solution by filtration. This recrystallization is repeated two to three times. Anal. Calcd. for C14H29O19Ru3 (Ru3(m3-O)(m-OAc)6(H2O)3]OAcH2O): C, 20.90; H, 3.63. Found: C, 20.76; H, 3.24. IR (KBr pellet): n(OAc) ¼ 1572 (sh), 1524, 1427 (sh), 1385 cm 1. Properties The product is air stable and soluble in polar organic solvents. B. TRI(PYRIDINE)-m3-OXO-HEXAKIS(m-ACETATE) TRIRUTHENIUM, Ru3(m3-O)(m-OAc)6(py)3

½Ru3 ðm3 -OÞðm-OAcÞ6 ðMeOHÞ3 ŠOAc þ 3 py þ 0:25 N2 H4 ! Ru3 ðm3 -OÞðm-OAcÞ6 ðpyÞ3 þ 0:25 N2 þ 3 MeOH þ HOAc

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Ruthenium Complexes

Procedure9 In a 100-mL round-bottomed flask equipped with a magnetic stir bar, [Ru3O(OAc)6(H2O)3]OAc (0.8 g, 0.1 mmol) is dissolved in 50 mL of methanol followed by 3 mL of pyridine. The reaction mixture was heated at reflux for 5 min and then allowed to cool to 0 C on an ice bath. To the cooled solution, about 5 mL of 95% N2H4 was added dropwise by pipette until the formation of a green precipitate was seen in the blue green solution. The suspension is then stirred for 15 min before the addition of two further drops of hydrazine. After five additional minutes, the green solid was collected by filtration and washed with 10 mL of water, 10 mL of methanol, and 3  10 mL of diethyl ether. After air dying, the solid was dried in vacuo. Yield: 0.42 g (46%). Anal. Calcd. for C27H33N3O13Ru3: C, 35.60; H, 3.65; N, 4.61. Found: C, 34.50; H, 3.35; N, 4.45. 1 H NMR (CDCl3): d OAc 2.09 (18H); d py 7.75 (6H), 7.99 (3H), 9.44 (6H). UV–vis (e in M 1 cm 1): lmax 249.0 (18,000), 402.1 (8400), and 919.9 (6800) nm. IR (KBr pellet): 1558, 1486, 1419, 1344, 764, 689, 631 cm 1. Cyclic voltammetry (1 mM in MeCN with 0.1 M Bu4NPF6, vs. Fc/Fc þ ): 450 mV (oxidation). Properties The product is air stable and soluble in organic solvents such as CH2Cl2 and MeCN, but insoluble in methanol. C. DI(AQUO)-m3-OXO-HEXAKIS(m-ACETATE)CARBONYLTRIRUTHENIUM(II, III, III), Ru3(m3-O)(m-OAc)6(CO)(H2O)2 ½Ru3 ðm3 -OÞðm-OAcÞ6 ðMeOHÞ3 ŠOAc þ CO þ NaBH4 þ 3 H2 O ! Ru3 ðm3 -OÞðmOAcÞ6 ðCOÞðH2 OÞ2 þ NaBðOAcÞH3 þ 3 MeOH þ 0:5 H2 & Caution. The third procedure involves pressurizing a flask with carbon monoxide. This should be performed carefully in a well-ventilated fume hood. Procedure A portion of [Ru3(m3-O)(m-OAc)6(H2O)3]OAc (4.16 g, 5.3 mmol) from step A is dissolved in about 100 mL of dry methanol in an oven-dried 500-mL Schlenk flask. This solution is sparged with N2 for 15 min with magnetic stirring, then while still flushing with N2, NaBH4 (0.262 g, 6.89 mmol, 1.3 equiv) is added in one portion. The flask is fitted with a sturdy rubber septum and secured tightly

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159

with tape or wire. The solution effervesces and changes from dark green to light green. The Schlenk flask inlet is connected to a CO source, and the flask is pressurized to ca. 1.3 atm of CO. The reaction is stirred at this pressure of CO for 12–15 h. Longer reaction times lead to lower yields. When the reaction is complete, the solution has assumed the deep purple color of the product. The reaction vessel is flushed with nitrogen, and the reaction mixture is then evaporated on a rotary evaporator at 40 C.* The product is purified by chromatography on a silica gel column (1.5 cm  20 cm) packed with CHCl3. About 0.5 g of the product is dissolved in about 5 mL of 3: 1 CHCl3/MeOH and loaded on the column. The product is eluted with 96% CHCl3/4% MeOH. The first band, containing the product, is deep purple in color. A second teal-colored band elutes after the product. The purple product is collected and the solvent is removed to yield a dark purple powder. Typical yield is 40–45%. Anal. Calcd. for C15H30O18Ru3 (Ru3(m3-O)(m-OAc)6(CO)(H2O)22 MeOH): C, 22.48; H, 3.77. Found: C, 22.87; H, 3.88. IR (KBr pellet, cm 1): n(CO) ¼ 1962; n(OAc) ¼ 1613, 1576, 1422. 1 H NMR (D2O): d OAc 1.93 (12H), 1.74 (6H). UV–vis (e in M 1 cm 1): 549 (2900), 379 (1700), 288 (4800) nm. Properties The product is soluble in water, but is only sparingly soluble in chloroform and methylene chloride. It can be solubilized in halogenated solvents by the addition of small amounts (ca. 5% by volume) of MeOH, EtOH, MeCN, or THF. Otherwise, the ancillary ligands are assumed to be H2O or MeOH, depending on the sample’s history. These coordinated water/methanol ligands are easily substituted over the course of several hours at room temperature. A variety of pyridyl ligands,10 isocyanides,18 and more complex ligands have been installed.16,17 The product is diamagnetic and is formulated as RuIIRuIIIRuIII with the carbonyl ligand bound to RuII. It is very stable in air both as a solid and in solution but is best stored as a solid in a sealed vial in a freezer if long-term storage (i.e., months to years) is needed. UV light (l < 250 nm) induces CO dissociation. Degraded product can be repurified by chromatography on silica. References 1. A. Spencer and G. Wilkinson, J. Chem. Soc., Dalton Trans. 8, 786–792 (1974). 2. S. Uemura, A. Spencer, and G. Wilkinson, J. Chem. Soc., Dalton Trans. 23, 2565–2571 (1973).

*

The reaction also proceeds if it is sparged with CO before the addition of the borohydride, but yields were found to be lower. The checkers used a Fischer–Porter bottle, which was operationally convenient, but gave no improvement in yield.

160

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3. A. Spencer and G. Wilkinson, J. Chem. Soc., Dalton Trans. 14, 1570–1577 (1972). 4. F. A. Cotton, J. G. Norman, A. Spencer, and G. Wilkinson, J. Chem. Soc. Chem. Commun. 16, 967–968 (1971). 5. J. A. Baumann, S. T. Wilson, D. J., Salmon, P. L. Hood, and T. J. Meyer, J. Am. Chem. Soc. 101, 11, 2916–2920 (1979). 6. H. Uehara, M. Abe, Y. Hisaeda, K. Uosaki, and Y. Sasaki, Chem. Lett. 35, 10, 1178–1179 (2006). 7. M. Abe, Y. Sasaki, Y., Yamada, K. Tsukahara, S. Yano, and T. Ito, Inorg. Chem. 34, 17, 4490–4498 (1995). 8. A. Sato, M. Abe, T. Inomata, T. Kondo, S. Ye, K. Uosaki, and Y. Sasaki, Phys. Chem. Chem. Phys. 3, 16, 3420–3426 (2001). 9. J. A. Baumann, D. J. Salmon, S. T. Wilson, T. J. Meyer, and W. E. Hatfield, Inorg. Chem. 17, 12, 3342–3350 (2002). 10. T. Ito, T. Hamaguchi, H. Nagino, T. Yamaguchi, H. Kido, I. S. Zavarine, T. Richmond, J., Washington, and C. P. Kubiak, J. Am. Chem. Soc. 121, 19, 4625–4632 (1999). 11. T. Ito, T. Hamaguchi, H. Nagino, T. Yamaguchi, J. Washington, and C. P. Kubiak, Science 277, 5326, 660–663 (1997). 12. C. H. Londergan and C. P. Kubiak, Chem. Eur. J. 9, 24, 5962–5969 (2003). 13. J. C. Salsman, C. P. Kubiak, and T. Ito, J. Am. Chem. Soc. 127, 8, 2382–2383 (2005). 14. J. C. Goeltz, C. J. Hanson, and C. P. Kubiak, Inorg. Chem. 48, 11, 4763–4767 (2009). 15. F. E. Sowrey, C. J. MacDonald, and R. D. Cannon, J. Chem. Soc., Faraday Trans. 94, 11, 1571–1574 (1998). 16. B. J. Lear and C. P. Kubiak, J. Phys. Chem. B 111, 24, 6766–6771 (2007). 17. B. J. Lear, and C. P. Kubiak, Inorg. Chem. 45, 18, 7041–7043 (2006). 18. K. Ota, H. Sasaki, T. Matsui, T. Hamaguchi, T. Yamaguchi, T. Ito, H. Kido, and C. P. Kubiak, Inorg. Chem. 38, 18, 4070–4078 (1999).

38. DI-m-CHLORO(ETHYLBENZOATE)DIRUTHENIUM(II), [(h6-etb)RuCl2]2 Submitted by ABRAHA HABTEMARIAM,* SOLEDAD BETANZOS-LARA,* and PETER J. SADLER* Checked by ESTER TRUFAN† and RICHARD D. ADAMS†

Dimeric arene complexes of the type [(h6-arene)RuCl2]2 are common starting materials in ruthenium chemistry. These Ru(II) dimers containing mono- and disubstituted arenes are generally prepared by reaction of RuCl33H2O with the appropriate 1,3- or 1,4-cyclohexadiene. The Ru(III) is reduced to Ru(II) with concurrent aromatization and p-binding of the cyclohexadiene.1,2 Coordinated arenes containing electron-withdrawing groups such as esters are thermally labile, and this property has been exploited synthetically for a variety of applications.3–7 *

Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK. Department of Chemistry, University of South Carolina, Columbia, SC.

†

38. Di-m-Chloro(Ethylbenzoate)Diruthenium(II)

161

Although some cyclohexadienes are readily available, many can be obtained easily by Birch reduction, which involves reduction with solutions of alkali metals in liquid ammonia, a source of solvated electrons, in the presence of alcohol as a proton source.8–10 In previous years, the Bouveault–Blanc procedure, which uses sodium metal and alcohol in liquid ammonia, was frequently employed for direct reduction of aromatic esters; however, it gave rise mainly to the corresponding substituted benzoic acid.11 Rabideau et al. reported a modified procedure;12 however, in our hands, this resulted in the reduction of the ester function to give benzoic acid. We have found that the Birch reduction of benzoic acid, followed by esterification, is an efficient procedure for the preparation of the corresponding 1,4-dihydro compound prior to the coordination of the arene to produce functionalized dimeric ruthenium–arene complexes.13 A. ETHYL-1,4-CYCLOHEXADIENE-3-CARBOXYLATE & Caution. Ammonia is a potent irritant to the respiratory system and the eyes. Metallic sodium reacts violently with water liberating highly flammable gases. An efficient fume hood must be used. C6 H5 CO2 Et þ H2 ! C6 H7 CO2 Et Procedure Liquid ammonia (600 mL) is condensed into a 2-L three-necked round-bottomed flask equipped with a dry ice/acetone condenser fitted with a calcium chloride guard tube, and a mechanical stirrer. The flask is kept at 198 K by a cooling bath (dry ice/acetone mixture). Benzoic acid (38.65 g, 0.32 mol) is placed into a 250mL round-bottomed flask and dry and freshly distilled ethanol (150 mL) is added. This solution is transferred into the ammonia solution by means of a cannula. Small pieces of sodium metal (21.7 g, 0.94 mol), which are kept under hexane, are added to the reaction mixture with rapid stirring over a period of 30 min. The reaction mixture turned dark blue and is stirred further for about 25 min. Then NH4Cl (35 g) is added. The color is discharged within about 2 min. The reaction mixture is stirred for a further hour, the cold bath is removed, and the ammonia left to evaporate under N2 flow and allowed to reach ambient temperature overnight. The white solid in the vessel is dissolved in chilled distilled water (500 mL), which is then acidified by a slow and careful addition of conc. hydrochloric acid (ca. 11 M) to pH 1–2.*

*

Owing to the presence of residual ammonia, addition of water may result in a very basic solution requiring that a large quantity of strong acid be added to reach the desired pH. Failure to properly acidify the solution may result in a highly reduced yield.

162

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This solution is placed in a separatory funnel and extracted (3  150 mL) with ether. The ether layers are combined and washed with brine solution and dried over anhydrous magnesium sulfate, filtered, and the solvent taken off on a rotary evaporator to leave a yellowish oily residue (yield 35.0 g). Vacuum distillation of the crude oil using a setup containing a fractionating column (13 cm long, diameter 0.5 cm; 0.08 mmHg/350–355 K) resulted in a clear colorless oil. 1 H NMR (CDCl3): d 5.94 (m, 2H), 5.87 (m, 2H), 3.80 (m, 1H), 2.72 (m, 2H). 1,4Dihydrobenzoic acid (35.0 g) is heated under reflux in dry ethanol (250 mL) and 98% sulfuric acid (17 mL) under nitrogen for 18 h. The pH is then adjusted to ca. 8 (monitored using an indicator paper) by the addition of a large excess of sodium hydroxide (25% w/v). This solution is placed onto a separating funnel, and brine (100 mL) is added to improve the layer separation. The solution is extracted with dichloromethane (3  150 mL). The organic layers are combined, dried over anhydrous magnesium sulfate, filtered, and the solvent removed on a rotary evaporator to give an oil. Vacuum distillation of the product using the setup described above resulted in a clear colorless oil [0.5 mmHg/319–321 K]. 1

H NMR (CDCl3): d 6.86 (m, 2H), 6.30 (m, 2H), 5.82 (m, 3H), 4.30 (q, 2H), 1.32 (t, 3H).* B. CHLORO(ETHYLBENZOATE)DIRUTHENIUM(II), [(h6-etb) RuCl2]2 2 C6 H7 CO2 Et þ 2 RuCl3  ðH2 OÞx ! ½ðC6 H5 CO2 EtÞRuCl2 Š2 þ H2 þ 2 HCl þ xH2 O Procedure RuCl3xH2O (1.01 g, 4.85 mmol assuming x ¼ 3) and ethyl-1,4-cyclohexadiene-3carboylate (3.69 g, 24.28 mmol) are stirred under reflux in dry ethanol (150 mL) under nitrogen for 10 h.† The mixture is allowed to cool to ambient temperature, the precipitate is filtered off, and the solid washed with minimal cold ethanol and then with diethyl ether. The solid is collected by filtration and dried in air (1.09 g, 88%). Anal. Calcd. for C18H20Cl4O4Ru2: C, 33.55; H, 3.13. Found: C, 33.53; H, 3.02. 1 H NMR (CDCl3): d 6.39 (d, 2H, J ¼ 6 Hz), 5.91 (t, 1H, J ¼ 6 Hz), 5.71 (t, 2H, *

Small amounts of benzoic acid and ethanol were detected by 1 H NMR analysis. The checkers distilled at 0.25 mmHg/309 K. † The reaction time is sufficient to produce the dimer in good quality and quantity; prolonged reaction times (up to 16 h) give the same result.

38. Di-m-Chloro(Ethylbenzoate)Diruthenium(II)

163

J ¼ 6 Hz), 4.40 (q, 2H, J ¼ 7 Hz), 1.35 (t, 3H, J ¼ 7 Hz). ESI-MS: 608.9 [M þ -Cl], 304.9 [M þ -Cl]. mp decomp. ca. 238 C. IR (n, cm 1): 3080 (CAr¼CAr), 1722 (C¼O). Properties The [(h6-etb)RuCl2]2 is a fine brick red powder that is readily soluble in chloroform and dichloromethane to afford yellow solutions that turn green after about 3 h accompanied by a black precipitate, indicating decomposition. It is also very soluble in DMF, methanol, and water to give dark yellow solutions, but sparingly soluble in acetone, ethanol, and ethyl acetate, and insoluble in hexane and other nonpolar solvents. It can be easily recrystallized from an aqueous solution to give crystals suitable for X-ray diffraction. Acknowledgments We thank WPRS/ORSAS (UK) and CONACyT (Mexico) for studentship support for S.B.-L. References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

R. A. Zelonka and M. C. Baird, Can. J. Chem., 50, 3063–3072 (1972). M. A. Bennett and A. K. Smith, J. Chem. Soc., Dalton Trans., 233–241 (1974). K. Umezawa-Vizzini and T. Randall Lee, Organometallics, 22, 3066–3076 (2003). Y. Miyaki, T. Onishi, S. Ogoshi, and H. Kurosawa, J. Organomet. Chem., 616, 135–139 (2000). B. Therrien, T. R. Ward, M. Pilkington, C. Hoffmann, F. Gilardoni, and J. Weber, Organometallics, 17, 330–337 (1998). A. M. Hayes, D. J. Morris, G. J. Clarkson, and M. Wills, J. Am. Chem. Soc., 127, 7318–7319 (2005). T. J. Geldbach, M. R. H. Brown, R. Scopelliti, and P. J. Dyson, J. Organomet. Chem., 690, 5055–5065 (2005). A. J. Birch and G. S. Rao,in: Advances in Organic Chemistry, Methods and Results, Taylor, E. C. Ed., Wiley-Interscience, New York, 1972, pp. 1–65. R. G. Harvey, Synthesis, 2, 161–172 (1970). P. W. Rabideau, Tetrahedron, 45, 1579–1603 (1989). H. O. House,in Modern Synthetic Reactions, 2nd ed., W. A. Benjamin, Inc., Meno Park, CA, 1972, pp. 150–151. P. W. Rabideau, D. L. Huser, and S. J. Nyikos, Tetrahedron Lett., 21, 1401–1404 (1980). M. Melchart, A. Habtemariam, O. Novakova, S. A. Moggach, F. P. A. Fabbiani, S. Parsons, V. Brabec, and P. J. Sadler, Inorg. Chem., 46, 8950–8962 (2007).

Chapter Nine

IRIDIUM COMPLEXES 39. THE DIPHOSPHINE tfepma AND ITS DIIRIDIUM COMPLEX Ir20,II(tfepma)3Cl2 Submitted by THOMAS S. TEETS,* TIMOTHY R. COOK,* and DANIEL G. NOCERA* Checked by JOHN C. GOELTZ† and CLIFFORD P. KUBIAK†

The two-electron mixed-valence compound, Ir2(tfepma)3Cl2 (tfepma ¼ CH3N(P[OCH2CF3]2)2), is synthesized by stoichiometric reaction of the chloro-1,5-cyclooctadieneiridium(I) dimer with tfepma. The bimetallic complex undergoes the unusual reaction of reversible addition of hydrogen across a single metal–metal bond.1–3 The complex contains a trigonal bipyramidal iridium(0) center and a square planar iridium(II) center. The iridium(II) center is coordinatively unsaturated and binds two-electron ligands. The bridging diphosphazane tfepma ligand is especially effective in supporting two-electron mixed valency of bimetallic cores comprising late transition metals.4–6 tfepma is prepared in two steps from commercial precursors. The first synthetic step affords MeN(PCl2)2 from the reaction of methylamine hydrochloride with phosphorus trichloride. Previous reports did not utilize an exogenous base,7,8 though we have found that in the presence of pyridine the reaction time can be shortened from 10 days to several hours, and yields are improved. The second synthetic step involves the reaction of MeN(PCl2)2 with a slight excess of 2,2,2-trifluoroethanol and triethylamine in *

Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139-4307. † Department of Chemistry, University of California at San Diego, San Diego, CA 61801. Inorganic Syntheses, Volume 35, edited by Thomas B. Rauchfuss Copyright Ó 2010 John Wiley & Sons, Inc.

164

39. The Diphosphine tfepma and its Diiridium Complex Ir20,II(tfepma)3Cl2

165

diethyl ether to furnish tfepma.9,10 The phosphine precursors are each prepared over the course of 2 days whereas the iridium complex described here is prepared in a few hours. General Except when noted, all manipulations were carried out in exclusion of air and moisture using glovebox and Schlenk techniques. 1,1,2,2-Tetrachloroethane was dried over anhydrous calcium chloride and filtered prior to use. Other solvents were dried by passing through an alumina column and sparged with argon. Methylamine hydrochloride was heated under vacuum at 125 C for 12 h prior to use. 2,2,2-Trifluoroethanol was dried by storage over molecular sieves, and triethylamine was dried by distillation from CaH2 under a nitrogen atmosphere. Anhydrous pyridine and phosphorus trichloride were used as received. A. BIS(DICHLOROPHOSPHINO)METHYLAMINE

MeNH3 Cl þ 2 PCl3 þ 3 C5 H5 N ! MeNðPCl2 Þ2 þ 3 C5 H5 NHCl Procedure In a nitrogen-filled glovebox, methylamine hydrochloride (41 g, 0.61 mol) is transferred to a 2–L two-necked round-bottomed flask equipped with a large Teflon-coated stir bar. The flask is fitted with a reflux condenser fitted with a nitrogen inlet and a rubber septum and removed from the glovebox.* Phosphorus trichloride (250 g, 1.8 mol) is added via cannula to give a colorless suspension, which is stirred and diluted with 250 mL of 1,1,2,2-tetrachloroethane. Pyridine (147 mL, 1.82 mmol) is then added via cannula to give a light pink mixture, which is heated to reflux for 16 h to give an orange, biphasic mixture. The mixture is allowed to cool to room temperature, causing a large amount of colorless pyridinium hydrochloride to precipitate from solution. The mixture is stirred at ca. 65 C until most of the solid redissolves, at which time 350 mL of hexanes is added via cannula. The resulting solution is stirred for 5 min and allowed to separate into two distinct layers. The top hexane layer is cannula transferred to a 1-L Schlenk flask. The extraction process is repeated with an additional 200 mL of hexanes and the top layer is combined with the first extract. The cloudy solution that results is evaporated. (Caution: Cold trap will contain PCl3.) The remaining crude product is purified by vacuum distillation at reduced pressure (60 C, 1 Torr) to remove any remaining 1,1,2,2-tetrachloroethane (first fraction). In the glovebox, *

The checkers weighed the hydrochloride quickly in air with no significant loss of yield. The reaction was conducted on 25% scale.

166

Iridium Complexes

the distilled product (second fraction) is filtered through glass wool to remove residual pyridinium hydrochloride, giving the product as a clear, colorless, lowviscosity oil. The yield is 84 g (60%). Anal. Calcd. for CH3Cl4NP2: C, 5.16; H, 1.30; N, 6.02. Found: C, 5.41; H, 1.27; N, 5.85. Properties Bis(dichlorophosphino)methylamine is a colorless oil that reacts rapidly with water; it is best stored frozen in a glovebox freezer. The 31 P{1 H} NMR spectrum in CDCl3 shows a singlet at 160.5 ppm vs. 85% D3PO4, and the 1 H NMR in CDCl3 consists of a triplet at 3.30 ppm (JH–P ¼ 3 Hz). B. BIS(BIS(TRIFLUOROETHOXY)PHOSPHINO)METHYLAMINE (tfepma) MeNðPCl2 Þ2 þ 4 CF3 CH2 OH þ 4 Et3 N ! MeN½PðOCH2 CF3 Þ2 Š2 þ 4 Et3 NHCl Procedure In the glovebox, bis(dichlorophosphino)methylamine (22.3 g, 95.8 mmol) is dissolved in 700 mL of diethyl ether in a 2-L two-necked round-bottomed flask with a Teflon-coated stir bar to give a clear, colorless solution. A flow adaptor is connected to one neck and a pressure-equalizing addition funnel and septum are connected to the other. The apparatus is removed from the glovebox and placed under a positive pressure of N2 through the flow adaptor. Triethylamine (60 mL, 430 mmol) is added via syringe to the addition funnel and added dropwise to the reaction mixture. If the triethylamine is not sufficiently dried, the reaction mixture becomes cloudy owing to a white precipitate, which forms from the hydrolysis of the P–Cl bond. The apparatus is placed in a cooling bath of dry ice/acetone and allowed to reach 78 C. Once cooled, trifluoroethanol (30.9 mL, 431 mmol) is added via syringe to the addition funnel and then added dropwise to the solution over 15 min. As the trifluoroethanol is added, a white solid forms and results in a thick white suspension upon completion of the addition. The suspension is removed from the cooling bath and stirred overnight at room temperature. The white solid is collected on a large frit and washed thoroughly with diethyl ether (4  500 mL). The diethyl ether is removed via a rotary evaporator to yield a slightly cloudy, colorless oil. The product is purified by vacuum distillation to remove excess trifluoroethanol, triethylamine, and residual triethylammonium chloride. At 0.35 Torr, the product fraction distills at a temperature of 60–65 C. The yield is 41 g (88%).

39. The Diphosphine tfepma and its Diiridium Complex Ir20,II(tfepma)3Cl2

167

Anal. Calcd. for C9H11F12NO4P2: C, 22.19; H, 2.28; N, 2.88. Found: C, 22.31; H, 2.32; N, 2.75. Properties The ligand tfepma, also a colorless oil, is air and moisture stable and can be handled under ambient atmosphere at room temperature. The 31 P{1 H} NMR spectrum in CDCl3 shows a singlet at 149.8 ppm vs. 85% D3PO4. The 1 H NMR in CDCl3 consists of a multiplet centered at 4.10 ppm (8H), and a triplet at 2.69 ppm (JH–P ¼ 3.9 Hz, 3H). C. Ir20,II(tfepma)3Cl2 ½IrðcodÞClŠ2 þ 3 MeN½PðOCH2 CF3 Þ2 Š2 ! Ir2 Cl2 fMeN½PðOCH2 CF3 Þ2 Š2 g3 þ 2 cod Procedure In the glovebox, an orange solution forms in a 100-mL Schlenk flask upon the addition of chloro-1,5-cyclooctadieneiridium(I) dimer11 (1.00 g, 1.49 mmol) to 50 mL of toluene. tfepma (2.25 g, 4.62 mmol) is dissolved in 5 mL of toluene and added dropwise to the [Ir(cod)Cl]2 solution, prompting a color change to dark red. Outside the glovebox, the flask is fitted with a reflux condenser and nitrogen inlet, and the solution is heated to reflux for 1 h under nitrogen, during which time a dark greenish-black solid forms and precipitates. Upon cooling to room temperature, the product settles. The dark yellow supernatant is removed by cannula filtration. The product is washed with 3  15 mL pentane and dried in vacuo to give a dark green powder. The yield is 1.84 g (64.6%). Anal. Calcd. for C27H33F36N3O12P6Ir2Cl2: C, 16.92; H, 1.74; N, 2.19. Found: C, 17.01; H, 1.71; N, 2.16. Properties Ir2(tfepma)3Cl2 is isolated as a microcrystalline dark green solid that can be stored indefinitely in a drybox. The solid dissolves in acetonitrile to give a yellow-orange solution. The 31 P{1 H} NMR spectrum of the compound in CD3CN consists of several broad features. Five distinct resonances are observed: a broad singlet at 33.0 ppm, a broad triplet at 47.8 ppm, and three multiplets centered at 64.5, 70.2, and 94.0 ppm. The 1 H NMR of the iridium compound in CD3CN shows two distinct methyl peaks: a triplet at 2.58 ppm (JH–P ¼ 10.5 Hz, 3H) and a broad singlet at 2.77 ppm (6H). Signals for the methylene protons of the trifluoroethoxy groups appear as a set of overlapping, broad resonances between 4.0 and 5.5 ppm.

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References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

A. F. Heyduk and D. G. Nocera, Chem. Commun. 1519 (1999). A. F. Heyduk and D. G. Nocera, J. Am. Chem. Soc. 122, 9415 (2000). T. G. Gray, A. S. Veige, and D. G. Nocera, J. Am. Chem. Soc. 126, 9760 (2004). T. G. Gray and D. G. Nocera, Chem. Commun. 1540 (2005). A. J. Esswein, A. S. Veige, and D. G. Nocera, J. Am. Chem. Soc. 127, 16641 (2005). T. R. Cook, Y. Surendranath, and D. G. Nocera, J. Am. Chem. Soc. 131, 28 (2009). J. F. Nixon, J. Chem. Soc. A 2689 (1968). R. B. King and J. Gimeno, Inorg. Chem. 17, 2390 (1978). M. Ganesan, S. S. Krishnamurthy, and M. Nethaji, J. Organomet. Chem. 570, 247 (1998). M. S. Balakrishna, T. K. Prakasha, S. S. Krishnamurthy, U. Siriwardane, and N. S. Hosmane, J. Organomet. Chem. 390, 203 (1990). 11. J. L. Herde, J. C. Lambert, and C. V. Senoff, Inorg. Synth. 15, 18 (1974).

40. HETEROLEPTIC CYCLOMETALATED IRIDIUM(III) COMPLEXES Submitted by LEONARD L. TINKER,* NEAL D. McDANIEL,* ERIC D. CLINE,* and STEFAN BERNHARD* Checked by ROSS D. PUTMAN† and THOMAS B. RAUCHFUSS†

The discovery of novel luminescent transition metal complexes has become the focus of many research efforts due to their widespread utility in a variety of fields.1 The versatility of such complexes is often determined by their photophysical and electrochemical properties, which can be ‘‘tuned’’ for a given purpose through judicious ligand modification.2 Early works that focus on ruthenium(II) complexes demonstrate a narrow range of excited-state tuning due to the thermal population of a quickly relaxing, nonemissive metal-centered (3 MC) state. Iridium(III) complexes have an increased ligand field stabilization energy, thus allowing for increased manipulation of the lowest unoccupied molecular orbital. In addition, such complexes form a mixed excited triplet state associated with metal-to-ligand charge transfer and ligand-centered transitions linked to the ancillary and cyclometalating ligands, respectively.3 The mixed nature of the excited state further facilitates the synthetic tuning of the photophysical and electrochemical properties of these highly luminescent materials. A facile route to heteroleptic iridium complexes involves the use of cyclometalated 2–arylpyridine derivatives of iridium dimers [Ir(Arpy)2Cl]2.4,5 2-Arylpyridines (Arpy) can be synthesized using the techniques described by Kro¨hnke6 *

Department of Chemistry, Princeton University, Princeton, NJ 08544. Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 08544.

†

40. Heteroleptic Cyclometalated Iridium(III) Complexes

169

(illustrated in this section) or by Suzuki coupling.7,8 Cleavage of the dimers [Ir(Arpy)2Cl]2 with neutral ligands is a reliable route to a range of heteroleptic iridium complexes. A. DI-m-CHLOROTETRAKIS[2-(2-PYRIDINYL-N)PHENYL-C] DIIRIDIUM(III), [Ir(ppy)2Cl]2

.

2 IrCl3 nH2O

N

N

4 N

Ir

Cl Cl

N

Ir N

(racemic)

In a 5-mL round-bottomed flask equipped with a reflux condenser is dissolved 2-phenylpyridine (46.1 mg, 297 mmol) in 2-methoxyethanol (1.8 mL) before adding water (0.6 mL) and IrCl3nH2O (n ¼ 4, 50.0 mg, 135 mmol). The mixture is heated to 120 C for 16 h, during which time a bright yellow product appears. The completed reaction is then cooled to room temperature and poured into water (10 mL). The product is isolated by vacuum filtration, washed with water (2  10 mL), and dried under reduced pressure. The reaction yields [Ir(ppy)2Cl]2 as a yellow solid that is typically triturated with hexanes followed by drying under reduced pressure and used without further purification. Yield: 63 mg, 59 mmol (87%). [Ir(ppy)2Cl]2 can be recrystallized by extraction into CH2Cl2 (10 mL) and clarifying the solution by filtering through a sintered glass frit. Hexanes (50 mL) are slowly added to the resulting solution. Cooling the solution below 5 C for at least 16 h affords the bright yellow product, which is isolated by vacuum filtration, washed with hexanes (2  10 mL), and dried under reduced pressure. Yield of recrystallization: 44 mg, 41 mmol (70%). Anal. Calcd. for C44H32Cl2Ir2N4: C, 49.29; H, 3.01; N, 5.23. Found: C, 48.81; H, 2.81; N, 5.12. 1 H NMR (CD2Cl2): d 9.25 (d, 4H, J ¼ 5.5 Hz), 7.94 (d, 4H, J ¼ 8.0 Hz), 7.80 (t, 4H, J ¼ 8.0 Hz), 7.56 (d, 4H, J ¼ 7.5 Hz), 6.82 (m, 8H), 6.60 (t, 4H, J ¼ 7.5 Hz), 5.87 (d, 4H, J ¼ 8.0 Hz). 13 C NMR (CD2Cl2): d 168.57, 152.04, 145.40, 144.57, 137.23, 130.93, 129.64, 124.22, 123.15, 121.95, 119.28.* *

The checkers treated the completed reaction with 5 mL of ice and isolated the bright yellow solid by gravity filtration, rinsing the reaction flask and the solid with 5 mL of methanol followed by ether. The crude product was judged pure by NMR spectroscopy.

170

Iridium Complexes

B. (2,20 -BIPYRIDINE-kN1, kN10 )BIS[2-(2-PYRIDINYL-kN)PHENYLkC]–IRIDIUM(III) HEXAFLUOROPHOSPHATE, [Ir(ppy)2bpy]PF6

N

N Ir

Cl Cl

N

(racemic)

2

N N

Ir N

N

N 2

NH4PF6

Ir

N

N

(racemic)

To a 5-mL round-bottomed flask are added [Ir(ppy)2Cl]2 (26.8 mg, 25.0 mmol), 2,20 bipyridine (9.0 mg, 57.6 mmol), and ethylene glycol (850 mL). The mixture is heated at 150 C for 12 h. The cooled reaction mixture is combined with water (20 mL) in a separatory funnel, and the aqueous solution is washed with diethyl ether (3  10 mL). The aqueous solution is heated to 70 C and treated with a solution of NH4PF6 (81.5 mg, 500 mmol) in water (0.5 mL). The solution is cooled to 5 C for at least 1 h prior to isolating the crude product by vacuum filtration. The product is washed with water (2  10 mL) and dried under reduced pressure. The product is then recrystallized by dissolving into acetonitrile (700 mL) in a 20-mL vial, which is placed in a secondary container of diethyl ether (20 mL). After at least 12 h, the product is isolated by decanting the supernatant, washing with diethyl ether (2  5 mL), and drying under reduced pressure. Yield: 36 mg, 45 mmol (90%). Anal. Calcd. for C32H24IrN4PF6: C, 47.94; H, 3.02; N, 6.99. Found: C, 47.83; H, 2.91; N, 6.98. 1 H NMR (acetone-d6): d 8.85 (dt, 2H, J ¼ 8.0, 1.0 Hz), 8.30 (ddd, 2H, J ¼ 8.0, 7.5, 1.5 Hz), 8.24 (m, 2H), 8.11 (ddd, 2H, J ¼ 5.5, 1.5, 0.5 Hz), 7.96 (ddd, 2H, J ¼ 8.0, 7.5, 1.5 Hz), 7.90 (dd, 2H, J ¼ 8.0, 1.0 Hz), 7.84 (ddd, 2H, J ¼ 6.0, 1.5, 0.5 Hz), 7.71 (ddd, 2H, J ¼ 8.0, 5.5, 1.0 Hz), 7.16 (ddd, 2H, J ¼ 7.5, 6.0, 1.5 Hz), 7.04 (ddd, 2H, J ¼ 8.0, 7.5, 1.0 Hz), 6.92 (dt, 2H, J ¼ 7.5, 1.5 Hz), 6.35 (ddd, 2H, J ¼ 7.5, 1.0, 0.5 Hz). 13 C NMR (acetone-d6): d 168.71, 156.99, 151.62, 151.38, 150.18, 144.99, 140.54, 139.61, 132.55, 131.33, 129.55, 125.90, 125.77, 124.54, 123.45, 120.87. Properties The UV–vis absorption spectrum of a 25 mM solution of [Ir(ppy)2bpy]PF6 in acetonitrile exhibits maxima (lmax, nm (emax, M 1 cm 1)) at 209 (3.5  104), 258 (4.3  104), 308sh (2.0  104), 379sh (5400), 414sh (3000), and 472sh (480). The emission spectrum with 337 nm excitation shows a maximum at 585 nm (F ¼ 0.0622) with a 390 ns lifetime. [Ir(ppy)2(bpy)]PF6 shows a reversible one-electron Ir(III/IV) oxidation wave (Ep ¼ 1.24 V vs. SCE, DEp ¼ 84 mV) and a reversible oneelectron bpy0/bpy 1 reduction wave (Ep ¼ 1.41 V vs. SCE, DEp ¼ 66 mV).

PF6

171

40. Heteroleptic Cyclometalated Iridium(III) Complexes

C. 2-(4-FLUOROPHENYL)-5-METHYL-PYRIDINE, F–mppy O O

O

N

Br F

N

H

F

F

NH4OAc

Br

N

To a 100-mL round-bottomed flask are added 2–bromo–40 –fluoroacetophenone (4.87 g, 22.4 mmol) and pyridine (50 mL). After stirring the mixture vigorously at room temperature for 1 h, the white pyridinium salt is collected by vacuum filtration and washed with diethyl ether (3  20 mL) (6.00 g, 20.3 mmol, 90% yield). In a 500-mL round-bottomed flask equipped with a reflux condenser, the pyridinium salt (5.00 g, 16.9 mmol) is dissolved in methanol (100 mL) before adding 2–methylacrolein (1.18 g, 16.8 mmol) and ammonium acetate (6.97 g, 90.5 mmol). The mixture is heated at reflux for 18 h during which time the reaction turns dark red. The reaction mixture is cooled to room temperature and then poured into water (400 mL). The colorless product is isolated by vacuum filtration, washed with water (150 mL), and dried under reduced pressure. This procedure yields F-mppy as a white solid. Yield: 1.69 g, 9.03 mmol (54%). TLC (silica, Sorbent 1624147, 10% ethyl acetate in hexanes, F–mppy Rf ¼ 0.18) and NMR analyses indicate that further purification is not necessary. Anal. Calcd. for C12H10FN: C, 76.99; H, 5.38; N, 7.48. Found: C, 76.86; H, 5.47; N, 7.54. 1 H NMR (CDCl3): d 8.48 (d, 1H, J ¼ 2.0 Hz), 7.92 (dd, 2H, J ¼ 8.5, 5.5 Hz), 7.56 (d, 1H, J ¼ 8.0 Hz), 7.53 (dd, 1H, J ¼ 8.0, 2.0 Hz), 7.12 (dd, 2H, J ¼ 9.5, 7.5 Hz), 2.35 (s, 3H). 13 C NMR (CDCl3): d 163.38 (d, JC–F ¼ 248.0 Hz), 153.64, 149.77, 137.81, 135.21, 131.80, 128.56 (d, JC–F ¼ 8.5 Hz), 119.97, 115.71 (d, JC–F ¼ 21.5 Hz), 18.23. D. DI-m-CHLOROTETRAKIS[5-FLUORO-2-(5-METHYL-2PYRIDINYL-N)PHENYL-C]DIIRIDIUM(III), [Ir(F–mppy)2Cl]2

4F 2 IrCl3.nH2O

N

N N

F F

Ir

Cl Cl

N

Ir N

(racemic)

F F

172

Iridium Complexes

In a 5-mL round-bottomed flask equipped with a reflux condenser is added a solution of F–mppy (55.5 mg, 297 mmol) in 2–ethoxyethanol (2.14 mL) followed by water (0.24 mL) and IrCl3nH2O (n ¼ 4, 50.0 mg, 135 mmol). The mixture is heated at 135 C for 16 h. The reaction mixture is cooled to room temperature and poured into water (10 mL). The precipitate is isolated by vacuum filtration, washed with water (2  10 mL), and dried under reduced pressure. The reaction yields [Ir(F–mppy)2Cl]2 as a yellow powder that is typically triturated with hexanes followed by drying under reduced pressure, and used without further purification. Yield: 75 mg, 63 mmol (93%). The [Ir(F–mppy)2Cl]2 can be recrystallized by dissolving in refluxing CH2Cl2 (150 mL) that is allowed to cool for 1 h while stirring. The solution is then clarified by filtration. The filtrate is heated to 40 C and concentrated to 10 mL under reduced pressure. The resulting solution is treated slowly with 10–20 mL of hexanes while stirring and then cooled to below 5 C for 16 h. An additional 10–20 mL of hexanes is added to the cooled solution and the product is allowed to crystallize at 5 C for another 16 h. The recrystallized product is isolated by vacuum filtration, washed with hexanes (2  10 mL), and dried under reduced pressure. Yield of recrystallization: 59 mg, 49 mmol (81%). Anal. Calcd. for C48H36Cl2F4Ir2N4: C, 48.04; H, 3.02; N, 4.67. Found: C, 47.65; H, 2.89; N, 4.54. 1 H NMR (CD2Cl2): d 9.02 (s, 4H), 7.79 (d, 4H, J ¼ 8.5 Hz), 7.70 (dd, 4H, J ¼ 8.0, 1.5 Hz), 7.53 (dd, 4H, J ¼ 8.5, 6.0 Hz), 6.55 (dt, 4H, J ¼ 8.5, 2.5 Hz), 5.42 (dd, 4H, J ¼ 10.0, 2.5 Hz), 2.02 (s, 12H). 13 C NMR (CD2Cl2): d 165.10, 162.72 (d, JC–F ¼ 252.0 Hz), 151.75, 147.10 (d, JC–F ¼ 6.0 Hz), 140.90, 138.79, 132.22, 125.46 (d, JC–F ¼ 9.5 Hz), 118.73, 116.71 (d, JC–F ¼ 18.0 Hz), 109.03 (d, JC–F ¼ 23.0 Hz), 18.90.*

Related Compounds Cleavage of [Ir(F–mppy)2Cl]2 by 2,20 –bipyridine gives [Ir(F–mppy)2(bpy)] þ . Relative to the ppy derivative, the fluorinated complex exhibits an increased emission energy, excited-state lifetime, and quantum yield of emission.9

* The checkers dissolved F-mppy (255 mg, 1.34 mmol) in 2-ethoxyethanol (9.6 mL) before adding water (1.2 mL). This solution is heated to reflux and then cooled back to room temperature under nitrogen prior to adding IrCl3nH2O (232 mg, 0.626 mmol). The cooled reaction mixture was worked up by addition of 30 mL of ice. After the ice had dissolved, the product was isolated by gravity filtration using filter paper and washed with 2 mL of cold methanol followed by ether to yield the yellow powder, which was judged pure by 1H NMR spectroscopy. Yield: 292 mg, 0.243 mmol (78%).

41. Oxygen and Carbon Bound Acetylacetonato Iridium(III) Complexes

173

References 1. M. S. Lowry and S. Bernhard, Chem. Eur. J. 12, 7970 (2006). 2. M. S. Lowry, W. R. Hudson, R. A. Pascal, and S. Bernhard, J. Am. Chem. Soc. 126, 14129 (2004). 3. M. S. Lowry, J. I. Goldsmith, J. D. Slinker, R. Rohl, R. A. Pascal, G. G. Malliaras, and S. Bernhard, Chem. Mater. 17, 5712 (2005). 4. S. Sprouse, K. A. King, P. J. Spellane, and R. J. Watts, J. Am. Chem. Soc. 106, 6647 (1984). 5. F. O. Garces, K. Dedeian, N. L. Keder, and R. J. Watts, Acta Crystallogr. C: Cryst. Struct. Commun. 49, 1117 (1993). 6. F. Kro¨hnke, Synthesis 1, 1 (1976). 7. O. Lohse, P. Thevenin, and E. Waldvogel, Synlett. 1, 45 (1999). 8. N. Miyaura, T. Yanagi, and A. Suzuki, Synth. Commun. 11, 513 (1981). 9. J. I. Goldsmith, W. R. Hudson, M. S. Lowry, T. H. Anderson, and S. Bernhard, J. Am. Chem. Soc. 127, 7502 (2005).

41. OXYGEN AND CARBON BOUND ACETYLACETONATO IRIDIUM(III) COMPLEXES Submitted by STEVEN M. BISCHOF* and ROY A. PERIANA* Checked by MARK R. RINGENBERG† and THOMAS B. RAUCHFUSS†

Tris(acetylacetonato-O,O) iridium(III) is a coordinatively saturated, stable species that has been examined spectroscopically1,2 and used in metal vapor deposition studies.3,4 Removal of one acac ligand (acac ¼ acetylacetonato or 2,4-pentanedionate) generates a family of bis-(acac-O,O) iridium(III) complexes exhibiting rich coordination chemistry. In 1976, Bennett and Mitchell isolated these (acac-O,O)2Ir(III)(R)(L) complexes as intermediates in yielding preparations of the (acac-O,O)3Ir(III) complex from the reaction of acetylacetone with IrCl3.5 In 2000, the catalytic properties of (acac-O,O)2Ir(III)(R)(L) were discovered as a part of a program on developing thermally stable, group VIII metal complexes containing O-donor ligands. For example, [Ir(m-acac-O,O,C3)(acac-O,O)(acacC3)]2 catalyzes the anti-Markovnikov hydroarylation of benzene with propylene to yield n-propylbenzene via a well-defined CH activation reaction.6

*

The Scripps Energy Laboratories, The Scripps Research Institute, Jupiter, FL 33458. Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

†

174

Iridium Complexes

The (acac-O,O)2Ir(acac-C3)(H2O) and [Ir(m-acac-O,O,C3)(acac-O,O)(acacC )]2 complexes are readily prepared, synthetically flexible starting materials for this class of compounds as shown previously by Bennett and Periana.5,7–9 Reacting either (acac-O,O)2Ir(acac-C3)(H2O) or [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2 with pyridines, alkyl amines, water, methyl or phenylating agents (Me2M or Ph2M where M ¼ Zn or Hg), mesitylene, benzene, cyclohexane, n-octane, and other organic reagents yields the alkyl or aryl derivatives, which exhibit rich coordination and reaction chemistry. 3

A. trans-BIS-(ACETYLACETONATO-O,O)(ACETYLACETONATOC3)AQUO IRIDIUM(III), (acac-O,O)2Ir(acac-C3)(H2O)

IrCl3 þ 3 NaHCO3 þ 3 CH3 COCH2 COCH3 ! ðacac-O; OÞ2 Irðacac-C3 ÞðH2 OÞ þ 3 NaCl þ 3 CO2 þ 2 H2 O Procedure Iridium trichloride hydrate (2.00 g, 5.67 mmol based on IrCl3.3H2O), sodium bicarbonate (2.00 g, 23.8 mmol, 4.2 equiv.), and acetylacetone (2,4-pentanedione, 20 mL, 196 mmol, 35 equiv.) are loaded into a 50-mL round-bottomed flask equipped with a magnetic stir bar and a water-cooled reflux condenser. The reaction mixture is refluxed for 48 h (acetylacetone bp  140 C) under argon (the reaction can also be carried out under air with an oil bubbler attached to the condenser). The reaction mixture is then cooled to room temperature and diluted with 25 mL of dichloromethane to precipitate a yellow solid, which is filtered with a sintered glass filter frit. Often, the yellow solid adheres to the walls of the flask,

41. Oxygen and Carbon Bound Acetylacetonato Iridium(III) Complexes

175

requiring removal by a metal spatula to load material on the frit for washing. The solid is washed with dichloromethane (2  25 mL) to remove remaining acetylacetone and (acac-O,O)3Ir. Isolation of (acac-O,O)3Ir can be done by workup of the dichloromethane layer; however, higher yielding procedures have now been reported.10 The isolated yellow solid (continue on to procedure B if interested in making [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2) is dissolved in 250 mL of deionized H2O at room temperature with vigorous stirring in a 500-mL roundbottomed flask, and the resulting solution is filtered. The solution is concentrated in vacuo to yield 0.86–1.30 g (1.70–2.55 mmol, 30–45%) of trans-(acac-O,O)2Ir (acac-C3)(H2O) as a yellow-orange powder. Care should be taken to not apply significant heat (>40 C) to remove the water in the vacuum concentration step as the product can be converted to [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2 at increased temperatures. Anal. Calcd. C, 35.50%; H, 4.57%. Found: C, 35.20%; H, 4.39%. 1 H NMR (D2O): d 5.53 (s, 2H), 5.47 (s, 1H), 1.90 (s, 12H), and 1.73 (s, 6H). 13 C NMR (90% D2O/10% CD3OD, 100 MHz): d 217.9, 188.0, 104.5, 50.0, 33.2, and 28.3. IR (diamond/ZnSe crystal, cm 1): 2970, 1738, 1678, 1556, 1516, 1386, 1275, 1200, 1014, 943, and 782. Properties The compound (acac-O,O)2Ir(acac-C3)(H2O) is quite soluble in water and methanol. It is slightly soluble in dichloromethane, chloroform, benzene, THF, toluene, and acetonitrile as well as acetic and trifluoroacetic acids. It is insoluble in hexanes and diethyl ether. The complex is air and water stable; however, when stored as a solid for long periods, a glovebox or desiccator should be utilized as the complex is slightly hygroscopic. Synthetically, (acac-O,O)2Ir(acac-C3)(H2O) is the precursor for procedure B as well as numerous other Ir(acac) motifs. Reaction with pyridines, alkyl amines, water, methyl or phenylating agents (Me2M or Ph2M where M ¼ Zn or Hg), mesitylene, benzene, cyclohexane, n-octane, and other organic reagents yields the alkyl or aryl derivative. B. BIS-(m-ACETYLACETONATO-O,O,C3)-BIS(ACETYLACETONATO-O,O)-BIS-(ACETYLACETONATO-C3) DIIRIDIUM(III), [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2

2 IrCl3 þ 6 NaHCO3 þ 6 CH3 COCH2 COCH3 ! ½Irðm-acac-O; O; C 3 Þðacac-O; OÞðacac-C 3 ފ2 þ 6 NaCl þ 6 CO2 þ 6 H2 O

176

Iridium Complexes

Procedure The yellow solid from preparation A is loaded into a 500-mL round-bottomed flask with reflux condenser and dissolved in 250 mL of deionized water. The mixture is refluxed for 4 h yielding a bright orange homogeneous solution. The water is removed in vacuo to yield an orange residue. The product is purified by elution with CHCl3 through a 6  45 cm column of neutral alumina. The fast-moving yellow/ orange band of the product (Rf  0.16) is followed by two by-products at Rf  0.25 and 0.29. Removal of the solvent yielded 0.69–1.33 g (0.71–1.36 mmol, 25–48%) of [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2. Anal. Calcd. C, 36.80%; H, 4.32%. Found: C, 36.69%; H, 4.41%. 1 H NMR (CDCl3): d 5.35 (s, 2H), 5.10 (s, 2H), 5.09 (s, 2H), 2.01 (s, 12H), 1.98 (s, 12H), and 1.93 (s, 12H). 13 C NMR (CDCl3): d 212.9, 203.4, 184.9, 103.4, 62.0, 39.7, 32.4, 30.2, and 27.4. IR (diamond/ZnSe crystal, cm 1) ¼ 2970, 1738, 1649, 1634, 1516, 1384, 1353, 1276, 1166, 1019, 938, 778, and 669. Properties [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2 shows excellent solubility in most organic solvents such as chloroform, dichloromethane, methanol, DMSO, and acetone. It is also soluble in many acids such as acetic, trifluoroacetic, and methanesulfonic acids. The thermally robust compound is stable to air and water. Samples have been stored for over 1 year without decomposition. Single crystals can be obtained by diffusion of alkane or aromatic solvents into chloroform or dichloromethane solutions of the complex. Heating [Ir(m-acac-O,O,C3)(acac-O,O) (acac-C3)]2 for extended periods in organic or acidic media leads to isolation of [Ir (m-acac-O,O,C3)(acac-O,O)(acac-C3)]2 or precipitation of iridium black. No evidence has been seen for formation of (acac-O,O)Ir(III) on prolonged heating. Reaction with pyridines, alkyl amines, water, methyl or phenylating agents (Me2M or Ph2M where M ¼ Zn or Hg), mesitylene, benzene, cyclohexane, n-octane, and other organic reagents yields the alkyl or aryl derivative. C H activation reactions can be performed in organic or acidic solvents. Hydroarylation with [Ir(m-acac-O, O,C3)(acac-O,O)(acac-C3)]2 occurs in benzene with primary alkenes.

C. trans-BIS-(ACETYLACETONATO-O,O)(ACETYLACETONATOC3)PYRIDINE IRIDIUM(III), (acac-O,O)2Ir(acac-C3)PYRIDINE

ðacac-O; OÞ2 Irðacac-C 3 ÞðH2 OÞ þ pyridine ! ðacac-O; OÞ2 Irðacac-C3 Þpyridine þ H2 O

41. Oxygen and Carbon Bound Acetylacetonato Iridium(III) Complexes

177

½Irðm-acac-O; O; C 3 Þ2 ðacac-O; OÞðacac-C3 ފ2 þ pyridine ! 2ðacac-O; OÞ2 Irðacac-C 3 Þpyridine Procedure A 100-mL Schlenk tube under an argon purge is loaded with 1.00 g (1.97 mmol) of (acac-O,O)2Ir(acac-C3)(H2O), procedure A, or 1.00 g (1.02 mmol) [Ir(m-acac-O, O,C3)(acac-O,O)(acac-C3)]2, procedure B, 40 mL (492 mmol) of CHCl3, and 10 mL (124 mmol) of pyridine. The mixture is heated at 60 C for 15 min to afford a homogeneous light yellow solution, which is allowed to cool to room temperature before filtering through a sintered glass filter frit. Removal of solvent gave >1.00 g (1.77 mmol, >90%) of trans-(acac-O,O)2Ir(acac-C3)pyridine. Anal. Calcd. C, 42.24%; H, 4.61%; N, 2.46%. Found: C, 41.95%; H, 4.65%; N, 2.74%. 1 H NMR (CDCl3): d 8.29 (d, J ¼ 5.0 Hz, 2H, pyridyl), 7.83 (t, J ¼ 7.7 Hz, 1H, pyridyl), 7.35 (t, J ¼ 7.0 Hz, 2H, pyridyl), 5.30 (s, 2H), 5.26 (s, 1H), 1.97 (s, 6H), 1.94 (s, 12H). 13 C NMR (CDCl3) d 213.2, 184.8, 149.3, 138.4, 124.9, 102.6, 39.9, 31.5, and 27.1. IR (diamond/ZnSe crystal, cm 1) ¼ 2970, 1738, 1669, 1639, 1548, 1535, 1382, 1354, 1276, 1235, 1159, 1061, 1028, 935, 776, 701, and 671. Properties The (acac-O,O)2Ir(acac-C3) pyridine complex is quite soluble in methanol, dichloromethane, and chloroform, and moderately soluble in THF. It is slightly soluble in water, benzene, and toluene. The complex is also soluble in acetic and trifluoroacetic acids. It is insoluble in hexanes and diethyl ether. The complex is air and water stable for extended periods. Addition of pyridine to complex from procedure A or B in organic or acid media leads to formation of (acac-O,O)2Ir (acac-C3)pyridine in situ, which drastically inhibits C–H activation; however, it does not stop it completely. Pyridine binds strongly through s-donation to help stabilize the electrophilic iridium(III). References R. J. Watts and D. Missimer, J. Am. Chem. Soc. 100, 5350 (1978). V. G. Isakova, I. A. Baidina, N. B. Morozova, and I. K. Igumenov, Polyhderon 19, 1097 (2000). E. F€arm, M. Kemell, M. Ritala, and M. Leskel€a, J. Phys. Chem. C 112, 15791 (2008). ¨ sterholm, and A. O. I. Krause, Catal. Lett. 114, R. J. Silvennoinen, O. J. Jylh€a, M. Lindbald, H. O 135 (2007). 5. M. A. Bennett and T. R. B. Mitchell, Inorg. Chem. 15, 2936 (1976). 6. T. Matsumoto, D. J. Taube, R. A. Periana, H. Taube, and H. Yoshida, J. Am. Chem. Soc. 122, 7414 (2000).

1. 2. 3. 4.

178

Iridium Complexes

7. R. A. Periana, X. Y. Liu, and G. Bhalla, Chem. Commun. 3000 (2002). 8. A. G. Wong-Foy, G. Bhalla, X. Y., Liu, and R. A. Periana, J. Am. Chem. Soc. 125, 14292 (2003). 9. G. Bhalla, X. Y. Liu, J. Oxgaard, W. A. GoddardIII, and R. A. Periana, J. Am. Chem. Soc. 127, 11372 (2005). 10. J. E. Collins, M. P. Castellani, A. L. Rheingold, E. J. Miller, W. E. Geiger, A. L. Rieger, and P. H. Rieger, Organometallics 14, 1232 (1995).

CONTRIBUTOR INDEX Adhikari, Debashis, 8, 24 Armanasco, Nicole L., 109 Badiei, Yosra, 50 Baker, Murray V., 109 Barnes, Alison G., 109 Bernhard, Stefan, 168 Bischof, Steven M., 173 Blackmore, Karen J., 92 Brown, David H., 109 Caporali, Maria, 96 Chen, Chien-Hong, 129 Chianese, Anthony, 84 Chiang, Karen P., 13, 41 Chung, Young Keun, 114 Clayton, Joshua, 56 Cline, Eric D., 168 Comba, Peter, 70 Cook, Timothy R., 164 Cowley, Ryan E., 13 Crabtree, Robert H., 84, 88 Ding, Keying, 43 Døssing, Anders, 67 Douvris, Christos, 56 DuBois, Daniel L., 132 Dudek, Lisa, 102 Dugan, Thomas R., 43, 48 Fete, Matthew G., 56 Frey, Anne Mette, 67 Garrett, Benjamin R., 84 Goeltz, John C., 164 Gonsalvi, Luca, 96 Hawthorne, M. Frederick, 63 Hayes, Paul G., 20

Hesler, Valerie J., 109 Heyduk, Alan F., 92 Hitomi, Yutaka, 74 Holland, Patrick L., 1, 13, 38, 41, 43, 48, 53 Jakob, Maik, 70 Jalisatgi, Satish, 63 Kajita, Yuuji, 74 Kerscher, Marion, 70 Kim, Sang Bok, 114 King, Benjamin T., 56 Kishima, Yoshihisa, 74 Kl€aui, Wolfgang, 120 Kodera, Masahito, 74 Kogut, Elzbieta, 45 Kubiak, Clifford P. 164 Kunz, Peter C., 120 Lee, Mark W., 63 Letko, Christopher S., 84 Leung, Chin Hin, 84 Liaw, Wen-Feng, 129 Lotz, Simon, 114 MacAdams, Leonard A., 30 Mack, Amanda E., 143 Matos, Karl, 56 McDaniel, Neal D., 168 Melzer, Marie M., 45 Michl, Josef, 56 Mindiola, Daniel J., 1, 8, 24, Nakagawa, Tomoyuki, 74 Nguyen, Andy I., 92 Nocera, Daniel G., 164 North, Michael R., 109

Inorganic Syntheses, Volume 35, edited by Thomas B. Rauchfuss Copyright Ó 2010 John Wiley & Sons, Inc. 179

180

Contributor Index

Ohki, Yasuhiro, 137 Ohta, Shun, 137 Periana, Roy A., 173 Peruzzini, Maurizio, 96 Piers, Warren E., 20 Pike, Robert D., 114 Puttnual, Chuleeporn, 30 Radius, Udo, 78 Rakowski DuBois, Mary, 132 Rauchfuss, Thomas B., 143 Roesky, Herbert W., 34 Ruckerbauer, David, 120 Safronov, Alexander V., 63 Sanchez Cabrera, Gloria, 8 Schaub, Thomas, 78 Stubbert, Bryan D., 38 Sun, Shouheng, 114 Sweigart, Dwight A., 114

Tachi, Yoshimitsu, 74 Tatsumi, Kazuyuki, 137 Teets, Thomas S., 164 Theopold, Klaus H., 30 Tinker, Leonard L., 168 Tran, Ba L., 8 Tranchemontagne, David J., 102 Valasˇek, Michal, 56 Varonka, Matthew S., 4, 45 Volkis, Victoria, 56 Voutchkova, Adelina, 88 Warren, Timothy H., 1, 4, 45, 50 Wielandt, J. Wolfram, 120 Wiese, Stefan, 45 Yaghi, Omar M., 102 Zanobini, Fabrizio, 96 Zharov, Ilya, 56 Zuno-Cruz, Francisco J., 8

SUBJECT INDEX (acac-O,O)2Ir(acac-C3)(H2O), trans-bis(acetylacetonato-O,O)(acetylacetonato-C3) aquo iridium(III), 174–175 (acac-O,O)2Ir(acac-C3)pyridine, trans-bis(acetylacetonato-O,O)(acetylacetonato-C3) pyridine iridium(III), 176–177 Acenaphthene(tricarbonyl)manganese(I) salt, 35:117–118 trans-bis(acetylacetonato-O,O) (acetylacetonato-C3)aquo iridium(III), 35:174–175 trans-bis(acetylacetonato-O,O) (acetylacetonato-C3)pyridine iridium(III), 35:176–177 N-Aryl diketiminates, 35:2–3 Arylthiolates, iron complexes, 35:137–142 Basic ruthenium acetate, 35:156 Bipidone (dimethyl-(3,7-dimethyl-9-oxo-2,4-bis (2-pyridyl)-3,7-diazabicyclo[3.3.1] nonane)-1,5-dicarboxylate), 35:72 (2,20 -Bipyridine)bis[2-(2-pyridinyl)phenyliridium(III) hexafluorophosphate, 35:170 Bis(bis(diethylphosphinomethyl)methylamine) nickel(0), 35:134 Bis(bis(trifluoroethoxy)phosphino)methylamine (tfepma), 35:166–167 Bis[bis(trimethylsilyl)amido]iron(II), 35:138–140 Bromide, salt of methylenebis(N-(t-butyl) imidazolium), 35:84–85 cyanocarbonyl iron derivative, 35: 131 Bromotricarbonylcyanoferrate(II), 35:131 Carbon-bound acetylacetonato iridium(III) complexes, 35:173–177 Cesium salt of 1-methylcarba-closo-dodecaborate( ), 35:57–58

salt of dodecahydroxy-closo-dodecaborate, 35:63–65 Chelating N-heterocyclic carbene ligand, 35:84–87 Chloro(1,5-cyclooctadiene)(1,3dimethylimidazolium-2-ylidene) rhodium (I), 35:89 Chromium tricarbonyl 1,3,5-trimethyl-1, 3,5triazacyclohexane complex, 35:111–112 acetonitrile nitrosyl complex, 35:67–69 aqua nitrosyl complex, 35:67–69 Cobalt Cyclopentadienyl)tris(dimethylphosphito derivative diketiminate complexes, 35:30–33 diketiminate complexes, 35:43–44 Copper diketiminate complexes, 35:50–54 tetradentate bispidine ligand dimethyl-(3,7dimethyl-9-oxo-2,4-bis(2-pyridyl)-3,7diazabicyclo[3.3.1]nonane)-1,5dicarboxylate, 35:70–73 tris(2-picolinyl)methane, complex, 35:74–76 Copper(II) bipidone complex, 35:72–73 Copper tert-butoxide, 35:51–52 Cr(CO)3(Me3TACH), tricarbonyl(1,3,5trimethyl-1,3,5-triazacyclohexane) chromium(0), 111–112 Cyanide tetraethylammonium (1,3-propanedithiolato) pentacarbonyldiiron derivative, 35:146 tetraethylammonium (1,3-propanedithiolato) tetracarbonyldiiron derivative, 35:145 Cyclometalated iridium(III) complexes, 35:168–172 bis(1,5-Cyclooctadiene)nickel(0), 35:123–124

Inorganic Syntheses, Volume 35, edited by Thomas B. Rauchfuss Copyright Ó 2010 John Wiley & Sons, Inc. 181

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Subject Index

(1,5-Cyclooctadiene)(bis-1,3dimethylimidazole-2-ylidene)iridium(I) hexafluorophosphate, 35:90 (Cyclopentadienyl)tris(dimethylphosphito-P) cobaltate(III), sodium salt, 35:125–128 1,3-Dialkyl-imidazol-2-ylidenes, 35:78–83 Di(aquo)-m3-oxo-hexakis(m-acetate)carbonyltriruthenium(II,III,III), 35:158–159 cis-Dichlorotetrakis(dimethylsulfoxide) ruthenium(II), 35:150–151 Dichloro(ethylbenzoate)ruthenium(II) dimer, 35:162–163 trans-Dichlorotetrakis(dimethylsulfoxide) ruthenium(II), 35:151 bis(Dichlorophosphino)methylamine, 35:165–166 bis(Diethylphosphinomethyl)methylamine, nickel complexes, 35:133–134 1,3-Diisopropyl-imidazol-2-ylidene, 35:80–82 1,3-Diisopropyl-imidazolium chloride, 35:79–80 Diketiminate ligands, 35:1–3 Diketiminate complexes, 35:3–19 chromium complexes, 35:32–33 cobalt complexes, 35:43–44 copper complexes, 35:50–55 iron complexes, 35:38–42 manganese complexes, 35:34–36 nickel complexes, 35:45–48 scandium complexes, 35:22–23 titanium complexes, 35:24–28 vanadium complexes, 35:30–32 zinc complexes, 35:36–37 Di-m-chlorotetrakis[2-(2-pyridinyl-N)phenyl-C] diiridium(III), 35:169–170 Di-m-chlorotetrakis[5-fluoro-2-(5-methyl-2pyridinyl-N)phenyl-C]diiridium(III), 35:171–172 2,6-Dimesitylbenzenethiol, 35:140–141 h6-N,N-Dimethylaniline, complex with (tricarbonyl)manganese(I), 35:118–119 1,3-Dimethyl imidazol-2-ylidene, 35:82–83 1,3-Dimethyl imidazolium iodide, 35:80 N,N0 -Dimethylimidazolium-2-carboxylate, 35:88–89 Dimethylsulfoxide cis-dichlorotetrakis(dimethylsulfoxide) ruthenium(II), 35:150–151 trans-dichlorotetrakis(dimethylsulfoxide) ruthenium(II), 35:151

Di(n-butyl)magnesium, 35:122–123 DIPPN¼C(Me)tBu, 16–17 DIPPN(C¼O)(tBu), 15–16 [DIPPN¼C(tBu)]2CH2, 17–18 DIPPNHC(O)tBu, N-pivaloyl-2,6,diisopropylanilide, 14–15 2,4-Di-tert-butyl-6-(tert-butylamino)phenol, 35:93–94 2,4-Di-tert-butyl-6-(tert-butylimino)quinone, 35:94–95 Dodecahydroxydodecaborate, 35: 63. Dodecamethylcarba-closo-dodecaboranyl radical, 35:61–62 Dodecamethylcarba-closo-dodecaborate( ) anion, 35:56–62 Ethyl-1,4-cyclohexadiene-3-carboxylate, 35:161–162 Fe[SC6H3-2,6-(mesityl)2]2, 141–142 2-(4-Fluorophenyl)-5-methyl-pyridine, 35:171 Hexaaquaruthenium tosylate, 35:152-155 Hexakis(acetylacetonato)trinickel(II), 35:121–122 Hydridobis(PNP)nickel(II) hexafluorophosphate, 35:134–135 Imidazolium carboxylates, N-heterocyclic carbene precursors, 35:88–90 Iminoquinone complexes, 35:92–96 Iodide 1,3-dimethyl-imidazolium salt, 35:80 1-methyl-3-isopropyl-imidazolium salt, 35:80 7-methyl-1,3,5-triaza-7phosphoniaadamantane salt, 35:100 tris(hydroxymethyl)methyl phosphonium salt, 35:99 Iridium (h2:h2-bis(1,3-dimethylimidazole-2-ylidene) complex, 35:90 cyclometalated complexes, 35:168–172 diphosphine (tfepma) complex, 35:164–167 N-heterocyclic carbene complexes, 35:88–90 acetylacetonato complexes, 35:173–177 Iron arylthiolates, 35:137–142 cyanocarbonyl complexes, 35:129–131, 145–146 Diketiminate complexes, 35:38–42

Subject Index bis[bis(trimethylsilyl)amido] complex, 35:138–140 (1,3-Propanedithiolato) derivatives, 35:143–145 Ir2(tfepma)3Cl2, tfepma, iridium complex, 167 [Ir(F-mppy)2Cl]2, di-m-chlorotetrakis[5-fluoro2-(5-methyl-2-pyridinyl-N)phenyl-C]diiridium(III), 171–172 [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2, 175–176 [Ir(ppy)2bpy]PF6, (2,20 -bipyridine-kN1, kN10 ) bis[22-(2-pyridinyl-kN)phenyl-kC]iridium(III) hexafluorophosphate, 170 [Ir(ppy)2Cl]2, 169 Lithium 2,4-bis(2,6-diisopropylphenylimido)pentyl derivative, 35:10–11 dodecamethylcarba-closo-dodecaborates( ) salt, 35:58–61 diketiminate derivative, 35:18–19 zinc diketiminate complex, 35:36–37 Low-coordinate diketiminate complexes, 35:2–3 Magnesium, dibutyl derivative, 35:122–123 Manganese acenaphthene(tricarbonyl) complex, 35:117–118 diketiminate complexes, 35:34–36 N,N-dimethylaniline(tricarbonyl)-complex, 35:118–119 naphthalene(tricarbonyl) complex, 35:118 tricarbonyl transfer agents, 35:114–119 Me2Im, 1,3-dimethyl-imidazol-3-ylidene, 82–83 Me2ImHI, 1,3-dimethyl-imidazolium iodide, 80 MeiPrIm, 1-methyl-3-isopropyl-imidazol-2ylidene, 82–83 MeiPrImHI, 1-methyl-3-isopropyl-imidazolium iodide, 80 2,4-Bis(mesitylimido)pentane, 35:5–6 nickel derivatives, 35:45–48 thallium derivatives, 35:6–7 Metal-organic frameworks MOF-5: Zn4O(terephthalate)3, 35:103–105 MOF-177: Zn4O(1,3,5-benzenetribenzoate)2, 35:106–107 Methylenebis(N-(t-butyl)imidazolium) bromide, 35:84–85

183

Methylenebis(N-(t-butyl)imidazol-2-ylidene), (1,5-cyclooctadiene)rhodium(I) derivative, 35:86–87 1-Methyl-3-isopropyl-imidazol-2-ylidene, 35:82–83 1-Methyl-3-isopropylimidazolium iodide, 35:80 7-Methyl-1,3,5-triaza-7-phosphoniaadamantane iodide, 35:100 Molybdenum, tricarbonyl 1,3,5-trimethyl-1,3,5triazacyclohexane complex, 35:112–113 Naphthalene, complex with (tricarbonyl)manganese(I), 35:118 Nickel acetylacetonato complex, 35:121–122 bis(diethylphosphinomethyl)methylamine complexes, 35:132–136 bis(1,5-cyclooctadiene) derivative, 35:123–124 diketiminate complexes, 35:45-50 Ni(PNP)2, bis(bis(diethylphosphinomethyl)methylamine)nickel(0), 134 Oxygen-bound acetylacetonato iridium(III) complexes, 35:173–177 Pentaaquanitrosylchromium sulfate, 35:67–69 7-Phospha-3-methyl-1,3,5-triazabicyclo[3.3.1] nonane, water-soluble bidentate (P,N) ligand PTN(Me), 35:100–101 bis(2-Picolinyl)methane, 35:75–76 Piperidone (dimethyl-(1-methyl-4-oxo-2,6-bis (2-pyridyl)piperidine)-3,5-dicarboxylate), 35:70–72 N-Pivaloyl-2,6-diisopropylanilide, 35:14–17 Potassium, 2,2,6,6-tetramethyl-3,5-bis(2,6diisopropylphenylimido)heptyl, 35:11–12 [PPN][Fe(CO)4(CN)], iron cyanocarbonyl complexes, 129–131 [PPN][Fe(CO)4(CN)], PPN salt of tetracarbonylcyanoferrate(0), 130 [PPN][FeIIBr(CO)3(CN)2], bis PPN salt of bromotricarbonylcyanoferrate(II), 131 n Pr2Im, 1,3-di-n-propyl-imidazol-2-ylidene, 80–82 n Pr2ImHCl, 1,3-di-n-propyl-imidazolium chloride, 79–80 1,3-Di-n-propyl-imidazolium chloride, 35:79–80 1,3-Di-n-propyl-imidazol-2-ylidene, 35:80–82 PTN(Me)

184

Subject Index

7-phospha-3-methyl-1,3,5-triazabicyclo[3.3.1]nonane, 35:100–101 Radical, dodecamethylcarba-closododecaboranyl, 35:56–62 Rhodium chelating N-heterocyclic carbene derivatives, 35:84–87 chloro(1,5-cyclooctadiene)(1,3dimethylimidazol-2-ylidene) complex, 35:89 {methylenebis(N-(t-butyl)imidazol-2ylidene)}(1,5-cyclooctadiene) complex, 35:86–87 N-heterocyclic carbene complexes, 35:88–90 [(h6-etb)RuCl2]2 dichloro(ethylbenzoate)ruthenium(II) dimer, 162–163 Ru3(m3-O)(m-OAc)6(CO)(H2O)2, di(aquo)-m3oxo-hexakis(m-acetate)carbonyltriruthenium(II, III, III), 158–159 [Ru3(m3-O)(m-OAc)6(H2O)3]OAc, tria(aquo)m3-oxo-hexakis(m-acetate)triruthenium acetate, 156–157 Ru3(m3-O)(m-OAc)6(py)3, tri(pyridine)-m3-oxohexakis(m-acetate)triruthenium, 157–158 Ruthenium acetates, 35:156–159 hexaaquo complex, 35:132–133 dimethylsulfoxide complexes, 35:148–151 ethylbenzoate complex, 35:162–163 tetroxide, 35:153 Scandium diketiminate complexes, 35:21–23 Scandium trichloride tris(tetrahydrofuran), 35:20–21 ScCl3(THF)3 scandium trichloride tris (tetrahydrofuran), 20–21 Silver-NHC reagent, 35:84–87 Na[(C5H5)Co{P(O)(OMe)2}3], sodium (h5cyclopentadienyl)tris(dimethylphosphitoP)cobaltate(III), 125–128 Sodium, salt of (h5-cyclopentadienyl)tris (dimethylphosphito-P)cobaltate(III), 35:125–128

Tetracarbonylcyanoferrate(0), 35:130 Tetrakis(hydroxymethyl)phosphonium chloride, 35:97–98 2,2,6,6-Tetramethyl-3,5-bis(2,6diisopropylphenylimido)heptane, 35:17–18 2,2,6,6-Tetramethyl-3,5-bis(2,6diisopropylphenylimido)heptyl cobalt complex, 35:43–44 iron complex, 35:41–42 scandium derivatives, 35:22–23 titanium derivatives, 35:27–28 vanadium derivatives, 35:28–29 tfepma, bis(bis(trifluoroethoxy)phosphino) methylamine, 35:166–167 Thallium diketiminate derivatives, 35:4–7 Titanium diketiminate complexes, 35:24–28 1,3,5-Trimethyl-1,3,5-triazacyclohexane complexes, 35:109–113 Tri(pyridine)-m3-oxo-hexakis(m-acetate) triruthenium, 35:157–158 Tris(hydroxymethyl)methyl phosphonium iodide, 35:99 Tris(hydroxymethyl)phosphine, 35:98 Tris(2-picolinyl)methane, copper(I) complex, 35:74–76 Tungsten, tricarbonyl 1,3,5-trimethyl-1,3,5triazacyclohexane complex, 35:113 Vanadium diketiminate complexes, 35:28–29 Water-soluble bidentate (P,N) ligand PTN(Me), 35:96–101 W(CO)3(Me3TACH), tricarbonyl(1,3,5trimethyl-1,3,5-triazacyclohexane)tungsten (0), 113 Zinc diketiminate complexes, 35:36–37 metal organic frameworks, 35, 103–107. Zirconium(IV) bis(aminophenolate) complexes, 35:92–96 Zn4O(terephthalate)2 metal-organic framework-5, 103–105 metal-organic framework-177, 106–107

FORMULA INDEX AgC15H24F6N4P, [Ag(CH2(t-BuC3H3N2)2]PF6, 86 B11C2H14Cs, Cs[MeCB11H11], 57 B11C12H36, Me12CB11, 61 B11C12H36Cs, Cs[Me12CB11], 58 B11C12H36Li, Li[Me12CB11], 60 B11C16H48N, NMe4[Me12CB11], 59 B12H12Cs2, Cs2[B12H12], 63 B12H12Cs2O12, Cs2[B12(OH)12], 63

C13H36B11, dodecamethylcarba-closododecaboranyl radical, 61–62 and dodecamethylcarba-closododecaborate( ), 56–62 C5H8N2, Me2Im, 82 C6H8N2O2, Me2ImCO2, 88 C6H15N3, TACH, 111 C7H12N2, 1-Pr-3-MeIm, 81 C7H12N2, t-BuC3H3N2, 84 C7H13N2l, 1-Pr-3-MeImHl, 80 C9H12O2, C6H7CO2Et, 161 C9H18ClN2, 1,3-Pr2ImHCl, 76 C12H10FN, 4-FC6H4-2-py-5-Me, 171 C15H26Br2N4, CH2(t-BuC3H3N2)2Br2, 84 C17H27NO, 2,6-(i-Pr)2C6H3NHC(O)CMe3, 14 C18H29NO, (t-Bu)2C6H4(O)N-t-Bu, 95 C18H31NO, (t-Bu)2C6H4(OH)NH-t-Bu, 93 C19H19N3, HC(6-(2-picolinyl))3, 75 C20H21N3O5, piperidone, 71 C21H26N2, HLMe,Me2, 6 C22H26NCl, 2,6-(i-Pr)2C6H3NC(Cl)CMe3, 15 C23H28N4O5, bispidine, 72 C23H29N, 2,6-(i-Pr)2C6H3NC(Me)CMe3, 16 C23H30N2, HLMe,Me3, 5 C27H18O6, 1,3,5-benzenetribenzoic acid, 106 C29H42N2, LMe,iPr2H, 9

C35H54N2, LtBu,iPr2H, 17 CoC11H23NaO9P3, Na{(C5H5)Co[P(O)(OMe)]3}3, 127 CoC35H53ClN2, (LtBu,iPr2)CoCl, 44 Co3C22H46O18P6, Co{(C5H5)Co[P(O)(OMe)2]3}2, 126 CrB2F8C10H15N6O, [Cr(MeCN)5(NO)](BF4)2, 68 CrC9H15N3O3, Cr(TACH)(CO)3, 111 CrC25H34N2Cl2, (LMe,Me2)CrCl2(THF), 32 CrH10NSO10, [Cr(H2O)5(NO)]SO4, 68 CsB11CH14, Cs[MeCB11H11], 57 CsB11C12H36, Cs[Me12CB11], 58 Cs2B12H12O12, Cs2[B12(OH)12], 63 CuC4H9O, CuO-t-Bu, 51 CuC21H22BF4N4, {[HC(6-(2-picolinyl))3]Cu(MeCN)}BF4, 76 CuC23H32Cl2N4O7, (bispidinate)CuCl, 73 CuC29H41ClN2, (LMe,iPr2)CuCl, 54 Cu2C53H65N4, [(LMe,Me3)Cu]2(toluene), 52

FC12H11N, 2-(4-fluorophenyl)-5-methylpyridine, 171 F12C9H11NO4P2, MeN(P(OCH2CF3)2)2, 166 FeC5NNaO4, Na[Fe(CN)(CO)4], 130 FeC6H12Cl2O1.5, FeCl2(THF)1.5, 39 FeC30H34NSSi2, [C6H3-2-6-(mes)2S]FeN(SiMe3)2, 142 FeC41H34BrN3O3P2, PPN[FeBr(CN)2(CO)3], 131 FeC41H34N2O4P2, PPN[Fe(CN)(CO)4], 130 FeC48H50S2, [C6H3-2-6-(mes)2S]2Fe, 141 Fe2C9H6O6S2, Fe2(pdt)(CO)6, 144 Fe2C17H26N2O5S2, Et4N[Fe2(pdt)(CN)(CO)5], 146 Fe2C24H72N4Si8, {Fe[N(SiMe3)2]2}2, 138 Fe2C58H82Cl2N4, (LMe,iPr2)2Fe2Cl2, 42

Inorganic Syntheses, Volume 35, edited by Thomas B. Rauchfuss Copyright Ó 2010 John Wiley & Sons, Inc. 185

186

Formula Index

IrC15H23O7, Ir(acac)2(C-acac)(H2O), 174 Ir2C27H33Cl2F36N3O2P6, [MeN(P(OCH2CF3)2)2]3Ir2Cl2, 167 Ir2C30H42O12, [Ir(acac)2(C-acac)]2, 175 Ir2C44H32F4N4, [Ir(2-Phpy-H)2Cl]2, 169 Ir2C48H40Cl2F4N4, [Ir(FC6H3-2-py-5-Me)2Cl]2, 172 IrC18H28F6N4P, [Ir(cod)(Me2Im)2]PF6, 90 IrC20H20NO6, Ir(acac)2(C-acac)(pyridine), 176 IrC32H24F6N4P, [Ir(2-Phpy-H)2(bipy)]PF6, 170 KC35H53N2, LtBu,iPr2K, 11 LiC12B11H36, Li[Me12CB11], 60 LiC29H41N2, LMe,iPr2Li, 10 LiC39H61N2O, LtBu,iPr2Li(THF), 18 LiC13H36B11, Li[CB11Me12], lithium dodecamethylcarba-closo-dodecaborates (–), 58–61 LMe,iPr2H, 9–10 LMe,iPr2Li, 10–11 (LtBu,iPr2)ScCl2, 22–23 (LMe,iPr2)ScCl2(THF), 21–22 (LtBu,iPr2)TiCl2, 27–28 (LMe,iPr2)TiCl2(THF), 25–26 (LMe,iPr2)VCl2, 28–29 (LMe,iPr2)CuCl, 53–54 (LMe,iPr2)2Fe2Cl2, 38–39 (LMe,iPr2)2Mn2I2, 35–36 (LMe,iPr2)MnI(THF), 34–35 (LMe,iPr2)2Ni Cl2, 48–49 (LMe,iPr2)ZnCl2Li(OEt2)2, 36–37 (LMe,Me2)CrCl2(THF)2, 32–33 (LMe,Me2)VCl2, 31–32 (LMe,Me3Cu)2(h2:h2-C7H8), 50–51 (LMe,Me3)Ni(2,4-lutidine), 46–47 (LMe,Me3)NiI(2,4-lutidine), 45–46 (LtBu,iPr2)CoCl, 43–44 (LtBu,iPr2)FeCl, 41–42 LtBu,iPr2K, 11–12 LtBu,iPr2H, 17–18 LtBu,iPr2Li, THF adduct, 18–19 MgC8H18, Mg(C4H9)2, 122 MnC11H11BF4NO3, [(Me2NC6H5)Mn(CO)3]BF4, 119 MnC13H8BF4O3, [(naphthalene)Mn(CO)3]BF4, 118

MnC15H10BF4O3, [(acenaphthene)Mn(CO)3]BF4, 117 MnC33H49ION2, (LMe,iPr2)MnI(THF), 34 Mn2C58H82I2N4, (LMe,iPr2)2Mn2I2, 35 MoC9H15N3O3, Mo(TACH)(CO)3, 112 NaC11H23CoO9P3, Na{(C5H5)Co[P(O)(OMe)2]3}, 127 NiC16H24, Ni(cod)2, 123 NiC22H54B2F8N2P4, {Ni-[(Et2PCH2)2NMe]2} (BF4)2, 136 NiC22H54N2P4, Ni[(Et2PCH2)2NMe]2, 134 NiC22H55F6N2P5, HNi[(Et2PCH2)2NMe]2PF6, 135 NiC30H38N3, (LMe,Me3)Ni(2,4-lutidine), 46 NiIN3, (LMe,Me3)NiI(2,4-lutidine), 45 Ni2C58H82Cl2N4, (LMe,iPr2)Ni2Cl2, 49 Ni3C30H42O12, [Ni(acac)2]3, 121 O4Ru, ruthenium tetroxide, 153 O12C14H26RuS2, [Ru(H2O)6](OTs)2, 150–151 P2C9H11F12NO4, MeN(P(OCH2CF3)2)2, 166 P2C11H27N, (Et2PCH2)2NMe, 133 P2CH3Cl4N, MeN(PCl2)2, 165 PC3H9O3, P(CH2OH)3, 98 PC4H12ClO4, [P(CH2OH)4]Cl, 97 PC4H12IO3, [MeP(CH2OH)3]I, 99 PC7H15IN3, 100 PC7H16N3, MePC5N2H10NMe, 100 RhC18H28F6N4P, [(cod)Rh(Me2Im)2]Cl, 89 RhC23H36F6N4P, [Rh(cod)(CH2(t-BuC3H2N2)2)]PF6, 86 RuC8H24Cl2O4S4, RuCl2(dmso)4, 150–151 RuC14H26O12S2, [Ru(H2O)6](OTs)2, 150–151 Ru2C18H20Cl4O4, (C6H5CO2Et)2Ru2Cl4, 162 Ru3C13H22O16, Ru3O(OAc)6(H2O)2(CO), 158 Ru3C14H27O18, [Ru3O(OAc)6(H2O)3]OAc, 156 Ru3C27H33N3O13, Ru3O(OAc)6(pyridine)3, 157 RuO4, 153 ScC12H24Cl3O3, ScCl3(THF)3, 20 ScC29H41Cl2N2, LMe,iPr2ScCl2, 22 ScC33H49Cl2N2O, LMe,iPr2ScCl2(THF), 21 SC24H26, C6H3-2,6-(mes)2SH, 140 S2C25H46Fe2N4O4, (Et4N)2[Fe2(pdt)(CN)2(CO)4], 145 S4C8H24Cl2O4Ru, RuCl2(dmso)4, 150–151

Formula Index TiC3H49Cl2N2O, (LMe,iPr2)TiCl2(THF), 25 TIC23H29N2, TILMe,Me3, 6 TiC35H53Cl2N2, (LtBu,iPr2)TiCl2, 27 VC25H34Cl2N2, (LMe,Me2)VCl2(THF), 31 VC29H41Cl2N2, (LMe,iPr2)VCl2, 28 WC9H15N3O3, W(TACH)(CO)3, 113

187

ZnC33H51Cl2LiN2O, (LMe,iPr2)ZnCl2(Et2O), 36 Zn4C24H12O13, Zn4O(terephthalate)3, 4, 103 Zn4C54H30O13, Zn4O(1,3,5benzenetribenzoate)2, 107 ZrC44H74N2O2, [(t-Bu)2C6H4(O)(N-t-Bu)]2Zr (THF)2, 96