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.