Mechanistic Unveiling of NH3BH3 Hydrolysis Catalyzed by a Cu–CAAC Complex

Abstract

Copper(I) cyclic(alkyl)(amino)carbene (Cu–CAAC) complexes represent rare non-noble metal catalysts capable of mediating the homogeneous hydrolysis of ammonia borane (NH3BH3). To gain mechanistic insights into the hydrolytic dehydrogenation of NH3BH3 catalyzed by (CAAC)CuCl, density functional theory (DFT) calculations were performed. Computational results suggest that the coordination of ammonia borane shifts from single-catalyst coordination to dual-catalyst cooperative coordination. This structural transition facilitates the formation of a thermodynamically favored intermediate and enables efficient B–H bond cleavage. The catalytic cycle encompasses crucial steps, including nucleophilic attack of H2O, the transformation of copper hydride, and O–H bond activation, ultimately leading to H2 evolution. The energy barrier of the rate-determining step is calculated to be 21.2 kcal/mol, which satisfies the kinetic criteria for a rapid reaction at room temperature.