Theoretical Study on Homogeneous Hydrogen Activation Catalyzed by Cationic Ag(I) Complex

Abstract

Recently, the Li group reported the first Ag-catalyzed hydrogenation of aldehydes in water, demonstrating the utility of Ag complexes in homogeneous catalytic transformations through hydrogen activation. In the present study, density functional theory methods have been used to study the mechanism of Ag-catalyzed hydrogen activation. Three possible pathways, including base-assisted hydrogen activation, ligand-assisted hydrogen activation, and oxidative addition were investigated. The ligand-assisted hydrogen activation is disfavored because the neutral biaryl phosphine ligand XPhos is not a competent proton acceptor and results in the destruction of the aromaticity of an aryl group. Oxidative addition of H2 on AgI complexes was also found to be unlikely. The resulting AgIII hydride complexes are highly unstable and can undergo spontaneous reduction due to the weakly electron-donating ligand and the relatively low electronegativity of hydrogen. By contrast, the base-assisted hydrogen activation mechanism is...