Electrocatalytic Dihydrogen Production with a Robust Mesoionic Pyridylcarbene Cobalt Catalyst

Abstract

A Co(III) complex with a mesoionic pyridylcarbene ligand is presented. This complex is an efficient electrocatalyst for H2 production at very low overpotential and high turnovers when using a (glassy carbon) GC electrode. The corresponding triazole complexes display no catalytic activity whatsoever under identical conditions. The remarkable robustness of the Co-C(carbene) bond towards acids is likely responsible for the high efficiency of this catalyst. The present results thus open new avenues for carbene-based ligands for generating functional models for hydrogenases.

Nickel Complexes of Pyridine‐Functionalized N‐Heterocyclic Carbenes: Syntheses, Structures, and Activity in Electrocatalytic Hydrogen Production

“…To the best of our knowledge, these are the first Ni‐NHC complexes reported to catalyze proton reduction. Only a few recent reports relate to proton reduction with metal‐NHC compounds, but these concern cobalt‐NHC complexes , …”

“…The two‐electron donor ligands such as phosphanes and amines have been widely used in combination with Co and Ni, metal centers. The N‐heterocyclic carbene (NHC) ligand is also a two‐electron donor, with strong binding properties comparable to that of phosphane ligands . Although Ni‐NHC complexes have found various applications in organometallic chemistry, the electrocatalytic properties of this kind of compounds so far mostly have been neglected.…”

“…The N-heterocyclic carbene (NHC) ligand is also a two-electron donor, with strong binding properties comparable to that of phosphane ligands. [14] Al-in square-planar geometries. The compounds of the ligand with an imidazole-based carbene revealed much higher activity in electrocatalytic proton reduction and better acid tolerance, although their overpotentials are higher than those of the benzimidazole-based compounds.…”

Heteromultimetallic Complexes with Redox‐Active Mesoionic Carbenes: Control of Donor Properties and Redox‐Induced Catalysis

“…In our pursuit of understanding the electronic structures, electrochemical properties, and donor properties of MICs, we have now turned our attention to MICs that are substituted with one or two ferrocenyl groups. In doing so, we wanted to test if the well‐defined electron transfer properties of the ferrocenyl group can be utilized to tune the donor properties of the MIC ligands and their metal complexes.…”

Electro‐ and Photocatalytic Generation of H2 Using a Distinctive CoII “PN3P” Pincer Supported Complex with Water or Saturated Saline as a Hydrogen Source

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Efficient electrocatalytic production of H 2 from mixed water/acetonitrile solutions was achieved using three new Co II complexes supported by the neutralp incer ligand bis(diphenylphosphino)-2,6-di(methylamino)pyridine ("PN 3 P"). Examples includeN -macrocyclic complexes, [7,[10][11][12] cobalt thiolates, [13,14] glyoxime-basedc ompounds, [8,[15][16][17][18][19][20][21][22] complexesw ith heterocyclic carbene ligands, [23,24] and cobalt complexes bearing polyphosphine ligands. The complex [Co(k 3 -2,6-{Ph 2 PNMe} 2 (NC 5 H 3 )Br 2 ]( 1)w as also able to photocatalytically reduce water to hydrogen in the presence of aRu(bpy) 3 2 + photosensitizer and ar eductant.

Dihydrogen represents an environmentally clean and renewable fuel with enormousp otential to address the world's energy demands.T he ideal source of hydrogenw ould be its combustion product, water,a nd using electrocatalytic reduction of neutralw ater or even sea water to produce H 2 is as ignificant goal whose successw ould offer as ourcet op ower the future.A ss uch, molecular catalysts, constructed of earth-abundant metals,f or this transformation are urgently sought and efforts to identifya nd understandt he abilities of such species represent an active field of research.

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