Contributions to the redox-behavior of [M(IV)(S(2)C(2)R(2))(2)](0) type dithiolene complexes of Ni, Pd, and Pt

Combined electrochemical and EPR spectroscopic investigations on [M(S(2)C(2)R(2))(2)](0) dithiolene chelates containing the metal in the formal oxidation state ''+4'' (M = Ni, Pd, Pt; R = CH3, C6H5, p-CH3C6H4 and p-CH3OC6H4) are reported. Spectroelectrochemically the ''M(III)'' species are easily obtained under reductive conditions. The electrochemical oxidation produces the ligand radical in all cases. Depending on the mode of the electrochemical potential (reduction/oxidation) the redox reaction ''M(III)'' complex reversible arrow ligand radical can be switched. The chemical oxidation of the [M(IV)(S(2)C(2)R(2))(2)] complexes with Br-2 yielded paramagnetic. formally ''M(V)'' containing Ni and Pt species. EHT-MO calculations are used for the explanation of the spin-density distribution in the [MS(4)] unit for the different oxidation state of the metal.