Boosting Hydrogen Evolution by In-Situ Converting a Benzimidazolium-bearing Nickel–NHC Complex into a Catalytically Active Species

Two new macrocyclic Ni–NHC complexes are synthesized and characterized for their activity towards proton and CO2 reduction catalysis. The benzimidazolium-bearing Ni-NHC complex only exhibits activity for H2 evolution by altering its chemical structure via its rapid reaction with CO2 upon reduction into the Ni(I) oxidation state. The benzimidazolium moieties are suggested to act as redox-active species to promote the H2 evolution catalysis.