Mechanism of reduction of cymantrene (tricarbonyl η5-cyclopentadienylmanganese) and its methyl carboximidate derivative

The mechanisms of electrochemical reduction of cymantrene, [Mn(CO)(3)(eta (5)-Cp)], and its ring-substituted methyl carboximidate derivative, [Mn(CO)(3)(eta (5)-C5H4C(NH)OMe)], were studied by voltammetry, in situ IR spectroelectrochemistry and preparative electrolysis. The product of one-electron reduction undergoes further chemical reactions. Comparison of the data obtained under atmosphere of argon and that of carbon monoxide leads to the conclusion that a ligand substitution reaction and dimerization participate in the overall reaction sequence. FTIR spectra recorded in situ suggest product dimerization, the formation of [Mn(CO)(5)](-) and, to a lesser extent, other unstable species. The dimer formation was not observed in the course of the reduction of the carboximidate.