NHC-Containing Manganese(I) Electrocatalysts for the Two-Electron Reduction of CO2

The synthesis and characterization of the first catalytic manganese N-heterocyclic carbene complexes are reported: MnBr(N-methyl-N-2-pyridylbenzimidazol-2-ylidine)(CO)(3) and MnBr(N-methyl-N-2-pyridylimidazol-2-ylidine)(CO)(3). Both new species mediate the reduction of CO2 to CO following two-electron reduction of the Mn-I center, as observed with preparative scale electrolysis and verified with (CO2)-C-13. The two-electron reduction of these species occurs at a single potential, rather than in two sequential steps separated by hundreds of millivolts, as is the case for previously reported MnBr(2,2-bipyridine)(CO)(3). Catalytic current enhancement is observed at voltages similar to MnBr(2,2-bipyridine)(CO)(3).