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-d ppf)(Cu(dppf))2]2+ (dppf=1,1'-bis(diphenylphosphino)ferrocene) at a pl atinum electrode in 1,2-dichloroethane was studied by cyclic voltammet ry and controlled potential electrolysis. The compound was found to un dergo an apparently reversible single-stepped three-electron transfer process involving the three non-interacting ferrocene moieties. The el ectrogenerated pentacation was, however, unstable towards fragmentatio n into the fairly stable Cu(I)(dppf.+) complex, [Cu(dppf)]2+, and the fugitive bis(diphenylphosphino)ferrocenium radical cation, [dppf].+, t he ultimate fate of which was the formation of protonated and oxygenat ed dppf derivatives upon reaction with water present in the reaction m edium. Subsequent back-reduction restored the starting dimer and produ ced the novel complex [Cu(dppf)(dppfO)]+, which was characterized by P -31 NMR spectroscopy.