A Highly Active N-Heterocyclic Carbene Manganese(I) Complex for Selective Electrocatalytic CO₂ Reduction to CO

We report here the first purely organometallic fac-[Mn^I (CO)₃ (bis-^Me NHC)Br] complex with unprecedented activity for the selective electrocatalytic reduction of CO₂ to CO, exceeding 100 turnovers with excellent faradaic yields (η_CO ≈95 %) in anhydrous CH₃ CN. Under the same conditions, a maximum turnover frequency (TOF_max ) of 2100 s^-1 was measured by cyclic voltammetry, which clearly exceeds the values reported for other manganese-based catalysts. Moreover, the addition of water leads to the highest TOF_max value (ca. 320 000 s^-1 ) ever reported for a manganese-based catalyst. A Mn^I tetracarbonyl intermediate was detected under catalytic conditions for the first time.