STEREOCHEMISTRY OF TRANSITION METAL COMPOUNDS

D. J. Brauer, and C. Kruger, The Stereochemistry of Transition Metal Cyclooctatetrae-nyl Complexes Di-h3,h3 -cyclooctatetraenedinickel, a Sandwich Compound with Two Enveloped Nickel Atoms, J. Organomet. Chem. 122, 265-273 (1976). 

Stereochemistry of the reactions of optically active organometallic transition metal compounds. H. Brunner, Top. Curr, Chem., 1975,56, 68-90 (74). 

Brunner, H. Stereochemistry of the Reactions of Optically Active Organometallic Transition Metal Compounds. 56, 67-90 (1975). 

Library of Congress Cataloging in Publication Data. Main entry under title Theoretical inorganic chemistry. (Topics in current chemistry 56). Bibliography p, Includes index. CONTENTS Jorgensen, C. K. Continuum effects indicated by hard and soft antibases (Lewis acids) and bases. - Brunner, H. Stereochemistry of the reactions of optically active organometallic transition metal compounds, [etc.]. 1. Chemistry, Physical and theoretical- Addresses, essays, lectures. I. Series. 

Douglas, B. E. Saito, Y. Stereochemistry of optically active transition metal compounds ACSSymp. Ser. 1980, 119. 

Chemistry is stereochemistry. After development of the fundamental synthetic methods and the structural characterization of many important compounds in such an expanding field as organometallic chemistry during the past 25 years, the problems demanding solution become more subtle, so that more elaborate techniques, e.g., kinetic and spectroscopic measurements, as well as stereochemical methods, gain in importance. Stereochemical information can be obtained by a variety of techniques. Hence, the study of such stereochemical aspects as cis-trans isomerism in square-planar and octahedral transition-metal compounds was a consequence of the increasing availability of IR spectrometers, and temperature-dependent NMR spectroscopy proved to be an extremely valuable technique for the study of nonrigid systems. 

This article is confined to organo-transition-metal compounds having chiral metal atoms whose optical activity has been demonstrated. Only those compounds are discussed in detail for which there is a choice with respect to the metal configuration and for which a separation or at least an enrichment of isomers with opposite metal configuration has been achieved. After the treatment of such topics as optical resolution, optical purity, optical stability, optical induction, stereochemistry of reactions, relative and absolute configurations, Table I (Section XVII) collects the information available for the compounds under consideration. 

Thus, with compounds of type (a), the stereochemistry of substitution, insertion, and cleavage reactions can be studied (8, II), whereas with compounds of type (b), the mechanism of racemization and epimerization at the chiral metal atom can be investigated (II, 92). In the following sections, representative examples of both types of study will be given, from which it will become evident how optically active labels at metal centers in organo-transition-metal compounds contribute to the elucidation of the stereochemical course of reactions. 

The coordination chemistry of oxalate (ox, C2042-) compounds provides a series of very interesting compounds from the stereochemical and magnetic points of view [197]. Most frequently the compounds form honeycomb layers in the presence of transition metal ions, in which the stereochemistry of the metal ion coordination sphere alternates between A and A. However, a three-dimensional homochiral structure is also possible. On the other hand, the negative charge of the oxalates necessitates the incorporation of cations between them, which provides the opportunity to introduce chirality and additional functionality in materials. The compound formed between homochiral manganese II oxalate and iron II tris bipyridinc (bpy) with formula [Mn oxls]2 " [Fcn(bpy)3]2+ crystallises in the space group fJ4 32. 

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