Trends in the hydricities of iron, cobalt, and nickel complexes and the metal-hydride reactivities with CO2

Abstract

Catalytic CO₂ hydrogenation is considered one of the most efficient strategies for CO₂ reduction, provided that we have efficient and selective catalysts. This paper explores a mass-spectrometric approach to rapidly compare the reactivities of 21 metal complexes (iron, cobalt, and nickel complexes with three bidentate N,N′-ligands and four bidentate P,P′-ligands) by energy-resolved MS/MS experiments. The experiments show relative hydricities of these complexes, singling out iron complexes with N,N′-ligands and cobalt complexes with P,P′-ligands as particularly reactive for hydride-donor reactions. Comparing these results with relative affinities of metal hydrides for CO₂ led to the conclusion that iron hydrides should be particularly suited for CO₂ hydrogenation reactions. The results, however, cannot account for the effects of the polar reaction environment in the condensed phase.