ANATION REACTIONS IN OCTAHEDRAL COBALT(3) COMPLEXES

We have undertaken the study of the rates of reaction and steric course for a number of reactions of the type cis-[CoX(SOL1)(en)2]2+ + Y- = cis- and trans-[CoXY(en)2]+ + SOL1, where X- and Y- are one of the ions chloride or bromide, in the solvent SOL1 and in other solvents SOL2 where SOL1 and SOL2 are N,N-dimethylform-amide (DMF), N,N-dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), methanol, or tetramethylene sulfone (TMS). The kinetic results all show an Sn1IP1a character. The steric course of the anation reaction varied markedly with Y- concentration and with the degree of association of the reacting complex and the anion Y-. In some cases SOL2 for SOL1 exchange is found to precede anation while in others direct anation of the reactant is observed. In general, isomerization of the products is observed and in some cases this isomerization is so fast that the products appear to form in the equilibrium ratio. That is, the initial product is in some cases the result of kinetic control, and in others is equilibrium controlled. © 1968, American Chemical Society. All rights reserved.