Influence of the Bis‐Carbene Ligand on Manganese Catalysts for CO2 Electroreduction

Abstract

AbstractFirst row transition metal complexes have attracted attention as abundant and affordable electrocatalysts for CO2 reduction. Manganese complexes bearing bis‐N‐heterocyclic carbene ligands defining 6‐membered ring metallacycles have proven to reduce CO2 to CO selectively at very high rates. Herein, we report the synthesis of manganese carbonyl complexes supported by a rigid ortho‐phenylene bridged bis‐N‐heterocyclic carbene ligand (ortho‐phenylene‐bis(N‐methylimidazol‐2‐ylidene), Ph‐bis‐mim), which defines a 7‐membered ring metallacycle. We performed a comparative study with the analogues complexes bearing an ethylene‐bis(N‐methylimidazol‐2‐ylidene) ligand (C2H4‐bis‐mim) and a methylene‐bis(N‐methylimidazol‐2‐ylidene) ligand (CH2‐bis‐mim), and found that catalysts comprising a seven‐membered metallacycle retain similar selectivity and activity as those with six‐membered metallacycles, while reducing the overpotential by 120–190 mV. Our findings reveal general design principles for manganese bis‐N‐heterocyclic carbene electrocatalysts, which can guide further designs of affordable, fast and low overpotential catalysts for CO2 electroreduction.