When electropolymerized, the complex Re(~bpy)(CO)~Cl (vbpy = 4-vinyl-4'-methyl-2,2'-bipyridine), as a polymeric film on a Pt electrode, electrocatalytically reduces C 0 2 to CO with turnover numbers greatly exceeding those observed for the analogous electrocatalytic reduction of C 0 2 by Re( bpy)(C0)3CI in homogeneous solution (bpy = 2,2 'b i py rid i n e) .
The complex cis-[Os(bpy)2(CO)H]+ (bpy is 2,2'-bipyridine) has been found to be an electrocatalyst for the reduction of C02 in CH$N containing 0.1 M tetra-n-butylammonium hexafluorophosphate at glassy carbon or Pt electrodes. Under anhydrous conditions CO is the dominant product, but addition of water results in up to 22% formate anion. Kinetic parameters derived by digital simulation of cyclic voltammograms under electrocatalytic conditions are consistent with a rate-determining associative step (kl) in which C02 undergoes a reaction with the direduced complex, [Os(bpy)z(CO)H]-, to form an intermediate. This intermediate either gives CO or a second intermediate which is a source of CO or formate by competitive pathways that follow the rate-determining step(s). On the basis of the results of isotopic labeling studies, neither the bound CO nor H-groups are involved in the reduction of CO1. The kinetics of reduction of C02 by the twice-reduced complexes ~is-[M(bpy)~(CO)R]-(M = Os, R = H, Me, Ph; M = Ru, R =
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