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

Abstract Herein, we report the synthesis and characterization of two manganese tricarbonyl complexes, Mn I (HL)(CO) 3 Br ( 1 a‐Br ) and Mn I (MeL)(CO) 3 Br ( 1 b‐Br ) (where HL=2‐(2’‐pyridyl)benzimidazole; MeL=1‐methyl‐2‐(2’‐pyridy)benzimidazole) and assayed their electrocatalytic properties for CO 2 reduction. A redox‐active pyridine benzimidazole ancillary ligand in complex 1 a‐Br displayed unique hydrogen atom transfer ability to facilitate electrocatalytic CO 2 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 CO 2 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 CO 2 activation by an earth‐abundant metal complex catalyst.