Hydride-like NH2δ- species-driven reductive amination over Co@CoO catalyst

Abstract

Selective synthesis of primary amines via reductive amination becomes an important research topic due to their wide applications. Various metal-based catalysts (Ru, Ir, Pt, Rh, etc.) have been developed; however, most systems suffer from low efficiency and poor stability. Here, we revealed that the hydride-like NH2δ- species, generated by the dissociation of NH3 over a core-shell structured Co@CoO catalyst is capable of accelerating the ammonolysis of Schiff bases, the reaction intermediates. This catalyst can handle various reductive aminations of aldehydes and ketones under mild conditions and run 21 times without deactivation. The combination of various spectroscopic measurements and computational modelling illustrated that this catalyst not only drives the dissociation of H2 to active Hδ- species, it also enables the homolytic and heterolytic cleavages of NH3 to NH2δ- species. D2 isotopic tracing experiment provided further evidence of the direct participation of hydride-like NH2δ- species in the ammonolysis of the Schiff bases. Theoretical calculations also verified the stable co-adsorption state of the Hδ- and NH2δ- species which allows the Schiff base to move freely on the surface of the CoO shell, resulting in the exceptional catalytic activity. This study demonstrates, for the first time, the potential of metal-oxide catalysts for the production of primary amines through reductive amination.