Tuning the Selectivity in the Hydrogenation of Aromatic Ketones Catalyzed by Similar Ruthenium and Rhodium Nanoparticles

Ru and Rh nanoparticles (NPs) RuI, RuII, RhI and RhII, stabilised by triphenylphosphine (PPh3) and diphenylphosphinobutane (dppb) were synthesised, characterised and applied as catalysts in the hydrogenation of several aromatic ketones. The effects of the nature of the metal and of the stabilising agent on the aryl versus ketone hydrogenation were studied. For Rh NPs, the coordination of arene dominates the interaction of the substrate with the NP, whereas the coordination of the ketone group was not evidenced. For Ru NPs, however, the results show that both arene and ketone coordinate to the NPs surface in a competitive manner. The properties of the stabilising ligands have a clear influence on the outcome of the reaction, and for the Rh‐catalysed reactions, products of hydrogenolysis were only formed if PPh3 was used as the stabiliser. The structure of the substrate was also a key factor for the selectivity. Name that tune: The selectivity of the arene versus ketone reduction of aryl ketones using Ru and Rh nanoparticles stabilized by triphenylphosphine and diphenylphosphinobutane depends on the metal, the stabilizing ligand, and structural factors in the substrates. Some general clues to understand this process are provided.