Understanding the Influence of Lewis Acids on CO2 Hydrogenation: The Critical Effect Is on Formate Rotation

Abstract

Lewis acids (LAs) have been shown to accelerate hydrogenation of CO2, but the underlying mechanistic details remain to be elucidated. We have employed computational methods to investigate how LAs affect CO2 hydrogenation with a range of known metal-hydrides (LnIr–H, LnRu–H, LnMn–H, LnCo–H). Our results show that LAs can alter the nature of the hydride–CO2 bond formation step, but do not lower its barrier. Instead, the accelerating effect of LAs is on the subsequent step, the rearrangement of the metal-formate σ-intermediate. These insights are essential for understanding the effect of LA additives on metal-mediated hydrogenations of CO2.