AN ELECTROCHEMICAL AND SPECTROELECTROCHEMICAL STUDY OF AN IRIDIUM BUCKMINSTERFULLERENE COMPLEX - EVIDENCE FOR C-60-LOCALIZED REDUCTIONS

The complex (eta(5)-C9H7)Ir(CO)(eta(2)-C60) has been studied by cyclic voltammetry (CV) in dichloromethane, tetrahydrofuran, and benzene. The CV in dichloromethane shows two quasi-reversible waves (E1/2 = -1.08 and -1.43 V vs internal ferrocene), which are assigned to C60-localized redox processes, and an irreversible oxidation (E(p) = + 0.72 V vs Fc+/Fc) apparently occurring at the metal atom. Modified potentials are observed in tetrahydrofuran, an effect very similar to that reported for free C60. Infrared spectroelectrochemistry shows that reduction of the complex by one and two electrons causes the nu(CO) IR band to shift to lower energy by 12 and 23 cm-1, respectively. These relatively small changes in frequency reflect small changes in electron density at the iridium center, thereby indicating ligand-centered rather than metal-centered reductions. Oxidation leads to irreversible loss of carbon monoxide from the complex. Small changes in the UV-vis spectrum of the complex also are observed upon reduction. Analysis of the electrochemical and spectral data suggests that complexation of C60 with the (eta(5)-C9H7)Ir(CO) moiety causes distinct but relatively minor perturbations in its electronic structure.