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-[Mn I (CO) 3 (bis-Me NHC)Br] complex with unprecedented activity for the selective electrocatalytic reduction of CO 2 to CO,e xceeding 100 turnovers with excellent faradaic yields (h CO % 95 %) in anhydrous CH 3 CN.U nder the same conditions,amaximum turnover frequency (TOF max )of2100 s À1 was measured by cyclic voltammetry,w hichc learly exceeds the values reported for other manganese-based catalysts.M oreover,t he addition of water leads to the highest TOF max value (ca. 320 000 s À1 )ever reported for amanganese-based catalyst. AMn I tetracarbonyl intermediate was detected under catalytic conditions for the first time.

Electrocatalytic Reduction of CO2 to Acetic Acid by a Molecular Manganese Corrole Complex

“…Aside from that, well-designed molecular metal complexes were developed to reduce CO 2 . In this regard, some molecular Mn-complexes like Mn(bipyridine)-pyrene, [9] N-heterocyclic carbene Mn I complex [10] and other similar complexes immobilized over supports like multi-walledcarbon-nanotubes (MWCNT) [11] or Nafion membrane [12] have been reported to reduce CO 2 to CO. Recently, we have observed that a cobalt(III) triphenylphosphine corrole complex exhibits potential dependent CO 2 reduction at pH 6 to produce methanol, ethanol, and low amounts of acetic acid (FE max.…”

Selective Electrocatalytic CO2 Reduction to CO by an NHC-Based Organometallic Heme Analogue

“…61 Evidence for the production of CO3 2− is obtained in the SEC-IR experiments. This was also the proposed mechanism for the purely organometallic manganese catalyst IV (Scheme 1) described above 29 and for (2'2-bipyridine)Re(CO)3Cl, which also catalyzes the CO2-to-CO/CO3 2conversion. In the latter case, a dimeric rhenium species was postulated as crucial intermediate.…”

“…At the onset of the catalytic wave (Figure 4, red), bands at frequencies of 1685 and 1645 cm −1 appear which are characteristic for HCO3 − and CO3 2− . 29 Under catalytic conditions no Fe 0 species is observed by SEC-IR and [LFe I (CO)] + represents the steady state species. When the potential is scanned beyond the catalytic wave, the current decreases indicating that CO2 is consumed, the baseline of the IR spectra shifts, reflecting the evolution of CO gas, (Figure 4, blue).…”

“…An organometallic analogue of the prominent manganese fac-tricarbonyl platform III has been obtained by replacing the potentially redox active bpy ligand with a bidentate bis(NHC) ligand (IV, Scheme 1). 29 This organometallic catalyst has been further modified with sterically bulky substituents on the peripheral N groups of the NHC ligands to avoid any potential dimerization. In fact, both Mn-NHC catalysts IV show turnover frequencies (TOFs) that exceed those of the parent Mnbpy catalyst III, presumably due to the more electron donating properties of the ligand.…”

“…In fact, both Mn-NHC catalysts IV show turnover frequencies (TOFs) that exceed those of the parent Mnbpy catalyst III, presumably due to the more electron donating properties of the ligand. 16,21,29,30 These studies lead one to consider a purely organometallic analogue 1 of the classical Fe-porphyrin V as a promising electrocatalyst for CO2 reduction (Scheme 1). Iron complexes supported by macrocyclic tetracarbene ligand scaffolds have been intensively studied in recent years, but the focus has been on their use in oxidation/oxygenation [31][32][33][34][35][36] and aziridination chemistry [37][38][39] as well as the isolation of high-valent and biorelevant reactive intermediates.…”