摘要：

Stereospecific effects are observed in many of the reactions of complex ions which contain optically active coordinating agents. Some examples of such stereospecificity are described, and an explanation of them is given which depends on an analysis of the stereochemistry of individual chelate rings and of the relationship between the rings in bis- and tris-chelate complexes. For example, it is shown that the dextro- and levo-forms of [Co en3]+3 can each exist in four conformational forms which differ in stability and which are in rapid equilibrium. One of these forms, designated herein as the "lel" form, is considerably more stable than the other three. The stereochemical requirements of the stable lel form are such that when a racemic 1,2-diamine is substituted for ethylenediamine all three ligands in the complex possess the same configuration. Hence, from a racemic 1,2-diamine, two isomers predominate at equilibrium, [Co(d-amine)3]+3 and its enantiomer [Co(l-amine)3]+3. The approach which has been developed makes possible predictions of relative stabilities and reactivities of isomers and allows the assignment of absolute configuration to chelate compounds.

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