Oxalate Formation in Electrochemical CO2 Reduction Catalyzed by Rhodium-Sulfur Cluster

Electrochemical reduction of CO2 catalyzed by a triangular rhodium complex [(RhCp*)3(μ3-S)2]2+ selectively produced formate and oxalate in the presence of Bu4NBF4 and LiBF4, respectively, under the controlled potential electrolysis at −1.50 V (vs. SCE) in CO2-saturated CH3CN. A solution IR spectrum evidenced the adduct formation between [(RhCp*)3(μ3-S)2]0 and CO2 as the possible precursor for the oxalate formation.