Abstract:
The electron spin resonance (ESR) spectra of the one-electron-reduction products of the 1,2-diphenyl- 1,2-ethenedithiolate complexes M(Ph2C2S2)2 (M = Ni, Pd, Pt) support the view that these reductions are mainly ligand based. Dc cyclic voltammetric studies of the above complexes also show an apparently quasi-reversible oxidation process in each case. ESR studies indicate that several species with slightly differing g values are formed in this process under the longer time scale of controlled-potential electrolysis. The 1,2-diphenyl-l,2-ethenedithiolate(2-)-SS' complexes M(dpe)(Ph2C,S2) (M = Ni(II), Pd(II), Pt(I1); dpe = 1,2-bis(diphenylphosphino)ethane) and M(PPh3)2(PhzCzSz) (M = Pd(I1)) were prepared, as described by previous workers, by ligand substitution reactions between the metal dithiolene complexes and the appropriate phosphine ligand. Ni(dpe)(Ph,C2S,) undergoes a reversible one-electron reduction to the corresponding nickel(1) complex and a reversible one-electron oxidation to give a long-lived species that is characterized by ESR spectroscopy as a complex of the previously unknown dithioketyl (PhzC2Sz)-.. The palladium and platinum 1,2-diphenyl-l,2-ethenedithiolate(2-)-S,S'complexes do not undergo reversible reduction but like the above nickel complex undergo reversible oxidation to give dithioketyl complexes.
