Electrochemistry of transition metal complex catalysts Part 8. One-electron oxidation of an iridium complex with a cyclohexane-derived tripod phosphine ligand - cyclic voltammetry and preparative electrolysis

The electrochemical oxidation of Ir(tdppcyme)(CO)Cl, tdppcyme = cis,cis-1,3 ,5-tris(di-phenylphosphine)-cis,cis-1,3,5-tris(methoxycarbonyl)cyclohexane, is investigated in dichloromethane-0.1 M tetrabutylammonium hexafluorophos phate at Pt electrodes with cyclic voltammetry, chronoamperometry and chron ocoulometry, as well as preparative electrolysis. While the primary one-ele ctron oxidation to Ir+II appears quasi-reversible in the electroanalytical experiments, the longer time scale of electrolysis allows the formation of an insoluble product by a follow-up reaction. By means of spectroscopic tec hniques as well as EXAFS and EDX experiments the structure of a dimeric di- mu -chloro di-iridiurn complex is deduced. (C) 2001 Elsevier Science Ltd. A ll rights reserved.