Rh4(CO)12-derived functionalized MCM-41-tethered rhodium complexes:: preparation, characterization and catalysis for cyclohexene hydroformylation

The preparation of Rh-4(CO)(12)-derived functionalized silicate MCM-41-tethered catalysts has been studied by infrared (IR) spectroscopy, X-ray diffraction (XRD) and N-2 adsorption-desorption. Silicate MCM-41 is first functionalized with phosphine, amine and thiol donor ligand groups. Then the functionalized MCM-41 is reacted with Rh-4(CO)(12) by coordination of surface donor ligands to the rhodium to produce phosphinated and aminated MCM-41-tethered unidentified rhodium carbonyl clusters and MCM-41-tethered [Rh(mu-S(CH2)(3)Si(O-s)(3))(CO)(2)](2) (where O-s represents surface oxygen). The functionalized MCM-41 and Rh/functionalized MCM-41 possess the structural ordering of mesoporous MCM-41, but exhibit reduced pore sizes, total pore volumes and BET surface areas. The tethered rhodium carbonyl catalysts behave differently with different donor ligands attached in cyclohexene hydroformylation under equimolar CO and H-2 at 2.7 MPa and 100 degreesC. Only the aminated MCM-41-tethered catalyst displays good activity, selectivity and recycling for the formation of cyclohexane carboxaldehyde. The influences of supported donor ligands on the activity and stability of tethered catalysts for hydroformylation are discussed. The mesoporous structure of MCM-41 is maintained stable during the catalytic reaction. (C) 2003 Elsevier B.V. All rights reserved.