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, MnI(HL)(CO)3Br (1a‐Br) and MnI(MeL)(CO)3Br (1b‐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 1a‐Br displayed unique hydrogen atom transfer ability to facilitate electrocatalytic CO2 conversion at a markedly lower reduction potential than that observed for 1b‐Br. Notably, a one‐electron reduction of 1a‐Br yields a structurally characterized H‐bonded binuclear Mn(I) adduct (2a’) 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.

Catalytic, Spectroscopic, and Theoretical Studies of Fe4S4-Based Coordination Polymers as Heterogenous Coupled Proton–Electron Transfer Mediators for Electrocatalysis

“…The shift of vibrational frequencies was also observed in recent SEIRAS studies on related manganese carbonyl compounds. 49 All the following vibrational frequencies, if not specifically mentioned, refer to frequencies observed in spectra collected at −1.8 V. The features at 2021, 1972, 1962, and 1926 cm −1 decrease with more negative potentials. The features at 2021, and 1926 cm −1 are assigned to 1, while the 1972 and 1962 cm −1 features are assigned to 2.…”

“…These peaks can be assigned to CO vibrational modes from different Mn species by comparing experimental IR spectra with published results or DFT predictions (Table S5). ,, It is notable that the vibrational frequencies from SEIRAS were measured under negative electric field and shifts of vibrational frequencies can be observed with changed applied potentials due to Stark effects. The shift of vibrational frequencies was also observed in recent SEIRAS studies on related manganese carbonyl compounds .…”

“… ,, It is notable that the vibrational frequencies from SEIRAS were measured under negative electric field and shifts of vibrational frequencies can be observed with changed applied potentials due to Stark effects. The shift of vibrational frequencies was also observed in recent SEIRAS studies on related manganese carbonyl compounds . All the following vibrational frequencies, if not specifically mentioned, refer to frequencies observed in spectra collected at −1.8 V. The features at 2021, 1972, 1962, and 1926 cm –1 decrease with more negative potentials.…”

Manganese(I) Diamine Electrocatalysts: Electrochemical Carbon Dioxide Reduction to Carbon Monoxide

“…Hence, a wide-range of ligands have been attached to a manganese tricarbonyl halide core [24][25][26], including N-heterocyclic carbene [27,28], non-aromatic diamine [29], pincer ligands [30], and P-coordinating ligands [31]. There are a wide range of recent examples exploring structure-activity and mechanistic questions of these organomanganese electrocatalysts [32][33][34][35][36][37][38][39].…”