METAL-METAL INTERACTIONS IN TETRAKIS(DIPHENYLPHOSPHINO)BENZENE-BRIDGED DIMETALLIC COMPLEXES AND THEIR RELATED COORDINATION POLYMERS

Electrochemical, EPR, and spectroelectrochemical methods have been used to prove electronic coupling through a 1,2,4,5,-tetrakis(diphenylphosphino)benzene bridging ligand connecting metal centers in several ni-, Pb-, and Pt-containing dimetallic complexes. These dimetalated complexes showed weak intervalence charge transfer (IT) bands and slightly shifted redox potentials in comparison with their monometallic models. A Marcus-Hush analysis of the energies of the IT bands for the electrochemically generated mixed-valence heterodimetallic complexes (Ni0-Pd(II) and Ni0-Pt(ii), respectively) established the magnitude of intermetallic electronic coupling. The weak thermal coupling observed in these dimetalated complexes is consistent with th very low conductivities (10(-8)-10(-10) OMEGA-1 cm-1) observed in the polymeric analogs of these complexes, namely, the newly prepared metal coordination polymers (M = Ni(II), Pd(II), Pt(II)) with 1,2,4,5-tetrakis(diphenylphosphino) benzene.