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

Abstract

We report here the first purely organometallic fac‐[MnI(CO)3(bis‐MeNHC)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 CH3CN. Under the same conditions, a maximum turnover frequency (TOFmax) 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 TOFmax value (ca. 320 000 s−1) ever reported for a manganese‐based catalyst. A MnI tetracarbonyl intermediate was detected under catalytic conditions for the first time.

Selective CO2 Splitting by Doubly Reduced Aryl Boranes to Give CO and [CO3]2−

“…[3] Theo ne-electron reduction of CO 2 occurs only at very cathodic potential values,m ainly because of the energy penalty associated with bending of the linear molecule upon electron uptake to furnish the [CO 2 ]C À radical. [7][8][9][10] Since the advent of frustrated Lewis pair (FLP) chemistry, increasing efforts have been devoted to the replacement of transition-metal catalysts by appropriate combinations of main-group Lewis acids and bases.I nt he context of CO 2 activation, ap lethora of capture products such as R 3 P-C(O)-O-BR' 3 are nowadays known. [1a] Some transition-metal com-pounds can act as nucleophiles toward CO 2 molecules and thereby transfer two electrons simultaneously onto the substrate,w hich is afterwards stabilized through p backbonding (see below).…”

A Manganese N‐Heterocyclic Carbene Catalyst for Reduction of Sulfoxides with Silanes

“…All compounds were used as received without further purification. The [Mn(bis‐NHC)(CO) 3 Br] complex was synthesised following the procedure already published by us . Solvents were dried according to standard procedures.…”

“…In particular, manganese‐mediated hydrosilylation reactions have proved to be a convenient method for the reduction of carbonyl groups, including aldehydes and ketones, esters, amides, carboxylic acids, CO 2 , and C=C/C≡unsaturated bonds . Last year, we disclosed the excellent reactivity of Mn(I) complexes supported by bidentate NHC ligands (NHC=N‐heterocyclic carbene) in the catalytic reduction of carbonyl groups . Motivated by these findings, we became interested in further exploring the potential of [Mn(bis‐NHC)(CO) 3 Br] complexes in reductions with silanes.…”

“…Motivated by these findings, we became interested in further exploring the potential of [Mn(bis‐NHC)(CO) 3 Br] complexes in reductions with silanes. Surprisingly, despite the enormous success of metal NHC complexes in catalysis, very few catalytic applications of Mn‐NHC complexes can be found in the literature . We report in this work the deoxygenation of sulfoxides to sulfides with silanes mediated by the manganese complex [Mn(bis‐NHC)(CO) 3 Br] bearing a bis‐N‐heterocyclic carbene ligand.…”

“…[7] Last year, we disclosed the excellent reactivity of Mn(I) complexes supported by bidentate NHC ligands (NHC=Nheterocyclic carbene) in the catalytic reduction of carbonyl groups. [8,9] Motivated by these findings, we became interested in further exploring the potential of [Mn(bis-NHC)(CO) 3 Br] complexes in reductions with silanes. Surprisingly, despite the enormous success of metal NHC complexes in catalysis, [10] very few catalytic applications of Mn-NHC complexes can be found in the literature.…”