Electrochemical Reduction of CO2 to CO Catalyzed by a Bimetallic Palladium Complex

The bis (triphosphine) ligand C6H4PCH2CH2P (C6H11) 222, m- (triphos) 2 (1), is synthesized by the reaction of m-bis (phosphino) benzene with 4 equiv of vinyldicyclohexylphosphine. Reaction of 1 with 2 equiv of Pd (CH3CN) 4 (BF4) 2 results in the formation of the bimetallic complex m- (triphos) 2Pd (CH3CN) 2 (BF4) 4 (2). A structural study of 2 confirms the presence of two Pd (triphosphine) (CH3CN) 2+ substituents at the meta positions of a benzene ring. Complex 2 catalyzes the electrochemical reduction of CO2 to CO in acidic dimethylformamide solutions. The kinetics of this reaction have been studied, and the reaction is 0. 5 order in catalyst and first order in CO2. This catalyst exhibits catalytic rates comparable to that of its monometallic analogues. Significantly higher turnover numbers are observed for 2 than observed previously for monometallic, bimetallic, and dendritic complexes of this class of catalysts.