摘要:
Dinuclear Ni(0) complexes [Ni-2(mu-dppa)(2)(mu-CNR)(CNR)(2)] (R = Me (1), n-Bu (2), and 2,6Me(2)C(6)H(3) (3); dppa = bis(diphenylphosphine)amine) were synthesized in good yields by reacting Ni(COD)2 with dppa and the corresponding isocyanide. The X-ray structure of complex 1 is reported. The electrochemistry and spectroelectrochemistry of each complex are also reported. Complex 2 exhibits an irreversible 1 e(-) reduction at -0.99 V vs ferrocene in its cyclic voltammogram. When the cyclic voltametry was performed in the presence of CO2, a substantial current enhancement was observed for the reduction wave. Spectroelectrochemical as well as isotope labeling studies show that 2 is singly reduced to a radical anion species that is reactive toward CO2, yielding the disproportionation products CO and CO32-. In the presence of H+ donors (residual water), reduction Of CO2 to formate is a competing process.