HETEROPOLYMETALLIC COMPLEXES OF 1,1'-BIS(DIPHENYLPHOSPHINO)FERROCENE, DPPF .9. ELECTROCHEMICAL OXIDATION OF THE DICOPPER(I) COMPLEX CATION [(MU-DPPF)(CU(DPPF))2]2+ - A MULTIELECTRON REDOX SYSTEM

The electrochemical oxidation of the homoleptic dimeric complex [(mu-dppf)(Cu(dppf))2]2+ (dppf=1,1'-bis(diphenylphosphino)ferrocene) at a platinum electrode in 1,2-dichloroethane was studied by cyclic voltammetry and controlled potential electrolysis. The compound was found to undergo an apparently reversible single-stepped three-electron transfer process involving the three non-interacting ferrocene moieties. The electrogenerated pentacation was, however, unstable towards fragmentation into the fairly stable Cu(I)(dppf.+) complex, [Cu(dppf)]2+, and the fugitive bis(diphenylphosphino)ferrocenium radical cation, [dppf].+, the ultimate fate of which was the formation of protonated and oxygenated dppf derivatives upon reaction with water present in the reaction medium. Subsequent back-reduction restored the starting dimer and produced the novel complex [Cu(dppf)(dppfO)]+, which was characterized by P-31 NMR spectroscopy.