Treatment of the racemic (Delta)(2)/(Lambda)(2) isomer of the tricationic Complex, [Co-3(aet)(6)](3+) ([1](3+)), with the optically active (Lambda(LLL))(2) isomer of the trianionic complex, [Co-3(L-cys-N,S)(6)](3-) ([2](3-)), afforded only the (Delta)(2)(Lambda(LLL))(2) isomer of the complex salt, [Co-3(aet)(6)][Co-3(L-cys-N,S)(6)] (3), the structure of which was determined by X-ray crystallography. The selective formation of this isomer was also observed when the racemic isomer of [1](3+) was treated with a 1:1 mixture of the (Delta(LLL))(2) and (Lambda(LLL))(2) isomers of [2](3-).