Unravelling the Mechanistic Pathway of the Hydrogen Evolution Reaction Driven by a Cobalt Catalyst

Bing Jiang, Marcos Gil-Sepulcre, Pablo Garrido-Barros, Carolina Gimbert-Suriñach, Jia Wei Wang, Jordi Garcia-Anton, Pau Nolis, Jordi Benet-Buchholz, Nuria Romero*, Xavier Sala, Antoni Llobet

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

Abstract

A cobalt complex bearing a κ-N3P2 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=−1.6 V vs Fc/Fc+. In the presence of 1 equiv of bis(trifluoromethane)sulfonimide, 1+ forms the cobalt hydride derivative CoIII(L)-H (22+), which has been fully characterized. Further addition of 1 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+.

Original languageEnglish
Article numbere202209075
Number of pages9
JournalAngewandte Chemie - International Edition
Volume61
Issue number40
Early online date3 Aug 2022
DOIs
Publication statusPublished - 4 Oct 2022

Keywords

  • Catalysis
  • Hydrogen Evolution Reaction
  • Ligands
  • Molecular Catalysis
  • Reaction Mechanism

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