Kinetics and Mechanism of the Outer-Sphere Oxidation of Metal Carbonyl Anions with Coordination Complexes Containing Chloride

Reactions of metal carbonyl anions, CpFe(CO)₂⁻, Re(CO)₅⁻, Mn(CO)₅⁻, CpMo(CO)₃⁻, CpCr(CO)₃⁻, and Co(CO)₄⁻, with CrCl₃•3S (S = THF, CH₃CN) and reactions of Mn(CO)₅⁻ and Re(CO)₅⁻ with [Co(o-phen) ₂Cl₂]ClO₄ are reported. Net oxidation/reduction chemistry is observed with formation of metal carbonyl dimers and CrCl₂•4S or Co(o-phen)₂Cl₂. Metal carbonyl halides are also observed and shown to arise from a secondary reaction of the metal carbonyl dimer with the oxidant. The products and rates are most consistent with outer-sphere electron-transfer reactions. Reactions of CpFe(CO)₂⁻ with CpFe(CO)₂X (X = Cl, Br, I) are also reported. The rate dependence on X is very small and in the order expected for nucleophilic substitution.