CO2 Activation with Manganese Tricarbonyl Complexes through an H‐Atom Responsive Benzimidazole Ligand

Herein, we report the synthesis and characterization of two manganese tricarbonyl complexes, MnI(HL)(CO)3Br (1 a‐Br) and MnI(MeL)(CO)3Br (1 b‐Br) (where HL=2‐(2’‐pyridyl)benzimidazole; MeL=1‐methyl‐2‐(2’‐pyridy)benzimidazole) and assayed their electrocatalytic properties for CO2 reduction. A redox‐active pyridine benzimidazole ancillary ligand in complex 1 a‐Br displayed unique hydrogen atom transfer ability to facilitate electrocatalytic CO2 conversion at a markedly lower reduction potential than that observed for 1 b‐Br. Notably, a one‐electron reduction of 1 a‐Br yields a structurally characterized H‐bonded binuclear Mn(I) adduct (2 a’) rather than the typically observed Mn(0)‐Mn(0) dimer, suggesting a novel method for CO2 activation. Combining advanced electrochemical, spectroscopic, and single crystal X‐ray diffraction techniques, we demonstrate the use of an H‐atom responsive ligand may reveal an alternative, low‐energy pathway for CO2 activation by an earth‐abundant metal complex catalyst.