Electrochemistry of [M 6(CO) 15] 2− anionic clusters (M = Co and Ir). Preparation and chemical characterization of [Ir 6(CO) 14(NCO)] − and of the radical anion [Ir 6(CO) 15] −. Proposed mechanism of formation of the hexanuclear substituted cluster [Ir 6(CO) 15Cl] −

Abstract

Electrochemical studies performed on [Ir 6(CO) 15] 2− show that the dianion undergoes stepwise oxidation to the congeners [Ir 6(CO) 15] n ( n = −1 or 0); only the monoanion is notably long-lived. By contrast the electrochemical oxidation of [Co 6(CO) 15] 2− shows that both the corresponding monoanion and neutral clusters are transient species. Information gained on the oxidation of [Ir 6(CO) 15] 2− in the presence of halide ions has enabled establishment of the mechanism of formation of the anion [Ir 6(CO) 15Cl] −, previously characterized by an X-ray study. This process of oxidation of [Ir 6(CO) 15] 2− can be also initiated by treating the hexanuclear complex with chemical oxidants such as [Fe(C 5H 5) 2] + and FeCl 3. The characterization of [N(PPh 3) 2][Ir 6(CO) 14(NCO)], obtained by chemical oxidation of [N(PPh 3) 2] 2[Ir 6(CO) 15 in the presence of [N(PPh 3) 2]N 3, is also reported.