Supported Rh2O3 sub-nanometer size particles for the direct amination of ethylene with piperidine

Abstract

Designing controlled nanostructured catalysts is always a demanding approach for bridging the gap between homogeneous and heterogeneous catalysis. In this report, 0.8–1 nm size Rh₂O₃ nanoparticles confined in silica meso-channels have been prepared through a facile template-assisted synthesis approach. The supported Rh₂O₃ particles presented excellent activity (TON = 543) towards the challenging direct addition of piperidine to ethylene under low pressure, with >99% selectivity towards the desired N-ethyl piperidine. The superior catalytic activity of the nanoclusters over large particles was predicted using the density functional theory and could be attributed to the binding mode of ethylene with the Rh species, wherein a weaker π-binding mode rather than the stronger σ-mode of binding of ethylene with the Rh species facilitates the C–N coupling reaction step.