Remarks on catalytic reduction of CO2, H+ and H2 by monovalent Ni

Abstract

Prompted by catalysis of CO₂ electroreduction by a tetraazamacrocyclic Ni(I)(cyclam) complex (cyclam = 1,4,8,11-tetraazacyclotetradecane), we examine theoretically the possibility of H₂ reduction by this molecule. We show that the process 2 Ni(I) + H₂ → 2 {Ni(II)(H⁻)} is thermodynamically facile, and that H₂ could be reduced by a binuclear Ni(I) complex in two concerted 1e⁻ processes. Our calculations also indicate that hydride complexes of Ni(III)(cyclam) are significantly unstable thermodynamically and therefore they are unlikely to serve as intermediates in process of H₂ evolution from water.