Unravelling the Mechanistic Pathway of the Hydrogen Evolution Reaction Driven by a Cobalt Catalyst.
Angew Chem Int Ed Engl
; 61(40): e202209075, 2022 Oct 04.
Article
em En
| MEDLINE
| ID: mdl-35922381
ABSTRACT
A cobalt complex bearing a κ-N3 P2 ligand is presented (1+ or CoI (L), where L is (1E,1'E)-1,1'-(pyridine-2,6-diyl)bis(N-(3-(diphenylphosphanyl)propyl)ethan-1-imine). Complex 1+ is stable under air at oxidation state CoI thanks to the π-acceptor character of the phosphine groups. Electrochemical behavior of 1+ reveals a two-electron CoI /CoIII oxidation process and an additional one-electron reduction, which leads to an enhancement in the current due to hydrogen evolution reaction (HER) at Eonset =-1.6â
V vs Fc/Fc+ . In the presence of 1â
equiv of bis(trifluoromethane)sulfonimide, 1+ forms the cobalt hydride derivative CoIII (L)-H (22+ ), which has been fully characterized. Further addition of 1â
equiv of CoCp*2 (Cp* is pentamethylcyclopentadienyl) affords the reduced CoII (L)-H (2+ ) species, which rapidly forms hydrogen and regenerates the initial CoI (L) (1+ ). The spectroscopic characterization of catalytic intermediates together with DFT calculations support an unusual bimolecular homolytic mechanism in the catalytic HER with 1+ .
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MEDLINE
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En
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Angew Chem Int Ed Engl
Ano de publicação:
2022
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Article