
%0 Journal Article
%A Fitzgerald, WR 
%A Watts, DW 
%T Octahedral cobalt(III) complexes in dipolar aprotic solvents. IV. Solvolysis and isomerization of dibromobisethylenediaminecobalt(III) ions inanhydrous NN-dimethylformamide and NN-dimethylacetamide
%J Australian Journal of Chemistry
%D 1966/06/01
%V 19
%N 6
%P 935-947
%K 
%R https://doi.org/10.1071/CH9660935
%U https://www.publish.csiro.au/paper/CH9660935 
%X The equilibrium system   (SOL)+Br-+cis-[CoBr2 em]+      = cis-[CoBr(SOL) en2]2++2Br-   &nbsp;                    =trans[CoBr2en2]2++Br-+SOL    where SOL represents either of the solvents NN-dimethylformamide (DMF) or NN-dimethylacetamide (DMA), has been studied. The compounds cis- [CoBr(DMF) en2](ClO4)2, and cis-[CoBr(DMA) en2]XO3,ClO4, have been isolated and thus it has been possible to study these equilibria using as starting materials both the cis- and trans-dibromo complexes (cis- and trans-[CoBr2 en2]+) and the solvento complexes (cis-[CoBr(DXA) en2]2+ and cis-[CoBr(DMF) en2]2+). The mechanism of the bromide entry reactions     cis-[CoBr(SOL) en2]2+ +Br- = cis- and trans-[CoBr2 en2]++SOL   is bimolecular in DMA while in DMF the reaction is dissociative: the rate showing bromide concentration dependence only in the concentration range where ion association is not complete. In both systems the isomerization proceeds mainly through the solvento complex; in dimethylacetamide there is evidence for a seven-coordinated intermediate. The isomerization equilibria are found to be bromide concentration dependent, cis-[CoBr2 en2]+ being favoured by high bromide concentrations. This is consistent with the lower stability of the trans-[CoBr2 en2]- ion pair with bromide ion. 
