Bimetallic Ru/Co nanoparticles stabilized by N-heterocyclic carbenes as catalysts for H/D exchange in N-heterocycles with deuterium gas

Abstract

A series of bimetallic ruthenium/cobalt nanoparticles (RuCo·IMes) stabilized with a N-heterocyclic carbene ligand, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), was prepared through co-decomposition of the Ru(COD)(COT) (COD = 1,5-cyclooctadiene; COT = 1,3,5-cyclooctatriene) and Co(COD)(η³-cyclooctenyl) precursors with H₂ (3 bar) using ligand/metal ratios of 0.2. The resulting nanoparticles, which exhibit mean sizes between 1.1 and 1.6 nm, were characterized using (high) transmission electron microscopy (TEM, HRTEM), inductively coupled plasma (ICP) analysis and X-ray photoelectron spectroscopy (XPS). Particularly, XPS measurements support the presence of both Co and Ru atoms on the nanoparticle surfaces and the coordination of the IMes ligand. Finally, the RuCo·IMes nanoparticles were applied to the hydrogen isotope exchange (HIE) reactions with deuterium gas (D₂) in N-heterocycles. The catalytic activity and deuterium incorporation selectivity of the RuCo·IMes nanoparticles were found to strongly depend on the specific substrate examined, generally providing lower activities and slightly higher selectivities with the presence of increasing amounts of Co in the nanoparticles.