Stereospecific Syntheses of Isomeric [Mn(CO)6‐n(CNMe)n]+ Complexes and Study of their Electrochemical Oxidations

The reactions of Mn(CO)5‐n(CNMe)nBr (n = 2, 3, 4) with either CO or CNMe in the presence of a halide acceptor are found to be stereospecific, with incoming ligand replacing the halide ion. These reactions were used in the syntheses of mer‐ and fac‐[Mn(CO)3(CNMe)3]PF6 and cis‐ and trans‐[Mn(CO)2(CNMe)4]PF6. A cyclic voltammetric study showed that the isomeric complexes had different E1/2 values. The difference in eases of oxidation was rationalized qualitatively based on the abilities of CO and CNMe to serve as π acceptors. This suggestion was supported quantitatively by theoretical calculations which defined the degree of stabilization of the HOMO levels in these complexes through π bonding.