Pushing the boundaries of gold catalysis

Gold has received much more attention as catalyst for selective oxidations than as a hydrogenation catalyst, mainly due to its limited capability to dissociate H2. We have recently found a way to activate gold based on the adsorption of nitrogen-containing bases on gold surfaces [1]. The activation of H2 was proposed to occur at the metal-ligand interface forming a tight ion pair induced by a frustrated Lewis pair (FLP) like structure, which was able to promote the heterolytic activation of H2 and the H-transfer to alkynes. Here we present a new Au catalyst supported on N-doped carbon that exhibited excellent activity and selectivity for hydrogenations. The intriguing structure of the novel gold heterogeneous catalyst, which could be also understood as frustrated Lewis pairs (FLP) interface, enables the heterolytic activation of molecular hydrogen, boosting gold catalytic activity while avoiding addition of external ligands. The catalyst demonstrated ~100% conversion and >99% selectivity (95% isolated yield) for the benchmark hydrogenation of phenylacetylene 1a. Notably, a gold catalyst prepared without addition of any ligand (Au/TiO2) showed only 4% conversion of 1a. Highly selective hydrogenation of numerous structurally diverse alkynes, epoxydes, nitro and aldehydes proceeded in moderate to excellent yield under mild conditions.