Reactions of Coordination Compounds in the Solid State. II. The Interconversion of the Isomers of Dichloro(triethylenetetramine)cobalt(III) Chloride, [Co(trien)Cl2]Cl, upon Heating in the Solid State

Abstract

Abstract The three isomers of the ion [Co(trien)Cl2]+, where trien=triethylenetetramine, have been synthesized and their interconversion upon heating in the solid state has been studied. The trans isomer changes to the β-cis isomer, which in turn is converted to the α-cis isomer. The changes have been followed by proton NMR spectroscopy. The first change cannot be explained by a twist mechanism. Experiments with the trans monohydrate or hydrochloride in sealed tubes or in an atmosphere of HCl show that the presence of H2O accelerates the conversion of the trans isomer to the cis-β isomer, and the presence of HCl accelerates the conversion of cis-β to cis-α, suggesting that the former conversion takes place through an aquation, followed by anation and for the latter conversion nucleophilic attack of a chloride ion on the cis-β isomer is important.