Chemical Versatility of [FeFe]-Hydrogenase Models: Distinctive Activity of [μ-C6H4-1,2-(κ2-S)2][Fe2(CO)6] for Electrocatalytic CO2 Reduction

The [FeFe]-hydrogenase model, [(μ-bdt)Fe2(CO)6] (1, bdt = benzene-1,2-dithiolato), displays distinctive activity from its analogous complex, [(μ-edt)Fe2(CO)6] (2, edt = ethane-1,2-dithiolato), for electrochemical CO2 reduction in acetonitrile with methanol or water as proton source. The maximum turnover frequency of 195 s–1 estimated for 1 is more than 4800 times higher than that of 2. The influence of reaction conditions on faradaic yield and product selectivity was investigated. Controlled potential electrolysis experiments of 1 under optimal conditions gave a good faradaic yield of 88%, with formic acid as major product (selectivity ≈81%) together with a small amount of CO (selectivity ≈ 11%) and H2 (selectivity ≈ 8%). Density functional theory calculations suggest a mechanism of bimetal synergistic catalysis for electrochemical CO2 reduction by 1.