Fast scan rate cyclic voltammetry has been used to elucidate the heterogeneous and homogeneous aspects of the redox chemistry of cis- and trans-[Mn(CN)(CO)2{P(OPh)3}(Ph2PCH2PPh2)]. The cis species, on oxidation, isomerizes to the trans conformation, and the various processes can be understood as components of a square reaction scheme. In solution phase, the homogeneous rate constant for isomeric conversion is found to be independent of solvent and concentration, with a value of 38 s-1 obtained by comparison with digitally simulated responses. The heterogeneous rate constants for the cis0/cis+ and trans0/trans+ couples in acetonitrile have values of 0.06 and 0.065 cm s-1 respectively. The cis or trans complex was readily immobilized on an electrode surface, either by mechanical attachment or by precipitation from solution. However, electrolysis in the solid state was strongly dependent on the identity of the supporting electrolyte anion. This dependence is similar to the Hofmeister series of anions with la...