AtomicallyPrecise Thiolated Copper–Hydride Nanoclusters as Single-SiteHydrogenation Catalysts forKetones in Mild Conditions

摘要

Copper–hydrides are known catalysts for several technologically important reactions such as hydrogenation of CO, hydroamination of alkenes and alkynes, and chemoselective hydrogenation of unsaturated ketones to unsaturated alcohols. Stabilizing copper-based particles by ligand chemistry to nanometer scale is an appealing route to make active catalysts with optimized material economy; however, it has been long believed that the ligand–metal interface, particularly if sulfur-containing thiols are used as stabilizing agent, may poison the catalyst. We report here a discovery of an ambient-stable thiolate-protected copper–hydride nanocluster [Cu25H10(SPhCl2)18]^3– that readily catalyzes hydrogenation of ketones to alcohols in mild conditions. A full experimental and theoretical characterization of its atomic and electronic structure shows that the 10 hydrides are instrumental for the stability of the nanocluster and are in an active role being continuously consumed and replenished in the hydrogenation reaction. Density functional theory computations suggest, backed up by the experimental evidence,that the hydrogenation takes place only around a single site of the10 hydride locations, rendering the [Cu25H10(SPhCl2)18]^3– one of thefirst nanocatalysts whose structure and catalytic functions are characterizedfully to atomic precision. Understanding of a working catalyst atthe atomistic level helps to optimize its properties and providesfundamental insights into the controversial issue of how a stable,ligand-passivated, metal-containing nanocluster can be at the sametime an active catalyst.