[{RhCl(CO)2}2]-Derived MCM-41-Tethered Rhodium Complex Catalysts via Phosphine, Amine and Thiol Ligands for Cyclohexene Hydroformylation

Abstract

Functionalized silicate MCM-41-tethered rhodium complexes derived from [{RhCl(CO)2}2] have been studied by infrared spectroscopy (IR), X-ray diffraction (XRD) and N2 adsorption-desorption. [{RhCl(CO)2}2] reacts with aminated MCM-41 to result in a splitting of the chloride bridge. The same result is presumed with phosphinated MCM-41. Thiolated MCM-41 is presumed to displace the chloride in the bridge with thiol ligands. The tethering of rhodium complexes to MCM-41 leads to reduced pore sizes, pore volumes and BET surface areas without altering the structural ordering of MCM-41. The MCM-41-tethered catalysts show distinct activities and resistance to rhodium leaching in cyclohexene hydroformylation under equimolar CO and H2 at 28 bar and 100 °C, depending on the nature of complexation of the supported donor ligands with the rhodium centre. The aminated MCM-41-tethered catalyst displays good activity, selectivity and recycling for the formation of cyclohexane carboxaldehyde. The mesoporous structure of MCM-41 remains stable during the reaction.