PROGRESS IN INORGANIC CHEMISTRY Volume 16 Advisory Board THEODORE L. BROWN UNIVERSITY OF ILLINOIS, URBANA, ILLINOIS JAMES P. COLLMAN STANFORD UNIVERSITY, STANFORD, CALIFORNIA F. ALBERT COXON TEXAS A&M UNIVERSITY, COLLEGE STATION, TEXAS RILEY SCHAEFFER INDIANA UNIVERSITY, BLOOMINGTON, INDIANA GEOFFREY WILKINSON IMPERIAL COLLEGE OF SCIENCE AND TECHNOLOGY, LONDON, ENGLAND PROGRESS IN INORGANIC CHEMISTRY EDITED BY STEPHEN J. LIPPARD DEPARTMENT OF CHEMISTRY COLUMBIA UNIVERSITY NEW YORK, NEW YORK . . VOLUME 16 INTERSCIENCE PUBLISHERS 1972 a division of JOHN WILEY & SONS, New York London Sydney Toronto Copyright @ 1972, by John Wiley & Sons, Inc. All rights reserved. Published simuitaneously in Canada. No part of this book may be reproduced by any means, nor transmitted, nor translated int6 a machine language with- out the written permission of the publisher. Library of Congress Catalogue Card Number: 59-1 3035 ISBN 0-471-54086-2 Printed in the United States of America. 109 7 6 7 1 8 S 4 3 Contents Halides and Oxyhalides of the Early Transition Series and Their Stability and Reactivity in Nonaqueous Media BY R. A. WALTON Department of Chemistry, Purdue University, Lafayette, Indiana . . . . . . . . . . . . . . . . 1 Stereochemical and Electronic Structural Aspects of Five-Coordination BY JOHNS . WOOD Department of Chemistry, University of Massachusetts, Amherst, Massachusetts . . . . . . . . . . . . . . 227 Transition Metal Complexes Containing Carbenoid Legands BY F. A. COTTON Department of Chemistry, Texas A and M University, College Station, Texas, and C. M. LUKEHART Department of Chemistry, Massachusetts Institute of Tech- nology, Cambridge, Massachusetts . . . . . . . . 487 Subject Index . . . . . . . . . . . . . . . . 615 Cumulative Author Index, Volumes 1-16 . . . . . . . . 627 V PROGRESS IN INORGANIC CHEMISTRY Volume 16 Progress in Inorganic Chemistry; Volume 16 Edited by Stephen J. Lippard Copyright © 1972 by John Wiley & Sons, Inc. HALIDES AND OXYHALIDES OF THE TRANSITION SERIES EARLY AND THEIR STABILITY AND REACTIVITY IN NONAQUEOUS MEDIA By R. A. Walton Department of Chemistry, Purdue University, La fayett e, Indiana . . . . . . . . . . . . . . . . I. Introduction 2 . . . . . . . . . A. General Considerations 4 . . . B. Nonexistent Halides and Oxyhalides 16 . . 11. Structures of the Halides and Oxyhalides 18 A. Noncluster Halides and Oxyhalides in . . Oxidation States VII, VI, V, and IV. 20 B. Noncluster Halides and Oxyhalides in . . . . Oxidation States 111, 11, and I. 32 C. Halides .C .o n.t a.in i.n g. C. lu. s.te r.s .o f. M. e.t al. . . Atoms. 35 111. Reactions of Metal Ha.li d.e s. a.n d. O. x.y h.a l.id e.s .o f. the Noncluster Type. 43 . . . A. Adduct Formation Without Reduction 43 1. Reactions of Halides with Donor Mole- . . . . . cules of Groups Vb and VIb 43 2. Reactions of Oxyhalides with Donor . . . Molecules of Groups Vb and VIb 94 . . . 3. Complex Halides and Oxyhalides 106 . . . . B. Adduct Formation with Reduction. 123 C. Oxidation Reactions Involving Low- . . . . . . . . Oxidation-State Halides. 133 . . . . . . D. Oxygen-Abstraction Reactions 135 . . . . . . . . . . E. Solvolysis Reactions 138 . . . . . . . . . F. Replacement Reactions. 162 . . . . . IV. Reactions of Cluster Metal Halides 164 . . . A. Triangular and Octahedral Clusters 165 . . . . . . . . . . 1. Adduct Formation 165 2. Solvolysis and Replacement Reac- . . . . . . . . . . . . . . . tions. 175 1 2 R. A. Walton 3. Reduction-Oxidation Reactions With- . . . . out Gross Structure Changes. 177 4. The Disruption of Metal Halide Clus- . . . . . . . . . . . . . . t e r s . . 181 B. Metal-Metal Bonding in Dinuclear . . . . . . . . . . . . . . . . Species. 184 . . . . . . . . . . . . V. Some Further Remarks 189 . . . . . . . . . . . . . . . . . . . . References 194 I. INTRODUCTION This chapter surveys the reactivities of halides and oxyhalides of the early transition series (titan- ium, vanadium, and chromium subgroups) and rhenium in nonaqueous media, and it is shown that these systems undergo a fascinating variety of reactions with a wide range of donor molecules. We shall devote most of our attention to the chlorides, bromides, and iodides be- cause these are the halides that generally exhibit the greatest variation i n behavior. Fluorides are briefly mentioned, but since they have been the subject of several review articles in recent years (25, 518, 584) we discuss only a few select examples dealing with the more recent and important aspects of their reactivity. In view of the wealth of data now available in the literature, no attempt is made to present a compre- hensive literature review. Rather, examples have been chosen to illustrate specific reactivity patterns and trends. There are three main reasons €or restricting this Halides and Oxyhalides of Early Transition Series 3 chapter to the halides of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, and rhenium. First, many of the halides and oxyhalides of groups V, and VI show a marked sensi- IV, tivity toward oxygen and moisture and consequently require similar handling techniques. This sensitivity in turn reflects both the lability of the metal-halogen bond to solvolysis and the tendency of these metals to form strong metal-oxygen bonds via oxygen insertion reactions involving the halides. Second, it is in this area of the periodic table that chlorine and bro- mine stabilize a wide range of oxidation states for certain of the transition elements. For example, molybdenum forms chlorides in all the oxidation states, ranging from VI to 11; these compounds are well char- acterized and their reactivities have been extensively studied. Likewise, the oxychlorides Mo02C12, MoOCl4, MoOCl3, MoOC12, and MoOCl are a l l well documented. On the other hand, related chlorides and oxychlorides of the other transition elements (e.g., the platinum metals) are much more limited, many are poorly char- acterized, and often they show little reactivity. Thus we have an opportunity to follow reactivity trends in closely related series of halides as the oxidation state is changed. Finally, it is apparent that change in the oxida- tion state of a metal halide is accompanied by striking 4 R. A. Walton structure changes. There is indeed an intriguing diversity of structure types, ranging from simple monomeric Tic14 and WClg to polynuclear cluster hal- ides such as Nb3C18, MogC112, and NbgC114. The rela- tionships between structure and reactivity are particu- larly interesting, and are one of the aspects covered i n this chapter. In view of the close similarity of the chemistry of the rhenium halides to those of molybdenum and tungsten, it is appropriate for us to include the halides of rhenium in this review. A. General Considerations Most metal halides have polymeric structures in the solid and liquid states, but several are monomeric (e.g., TiClq, VCl4, WFgl WClg) and others are of the cluster type, wherein a finite number of metal atoms are held together by metal-metal bonds. If we define the latter class of compounds along the lines proposed by Cotton (1801, as "those containing a finite group of metal atoms which are held together entirely, mainly, or at least to a significant extent, by bonds directly between the metal atoms even though some non- metal atoms may be associated intimately with the cluster," then we can conveniently classify metal hal- ides as being o€ the cluster type or otherwise. Since certain reactivity differences exist between these two general structural classes, let us discuss them sep- arately. Tables I to I11 list the halides that are