Hydroformylation of 1-Octene under Atmospheric Pressure Catalyzed by Rhodium Carbonyl Thiolate Complexes Tethered to Silica

Abstract

The silica-tethered rhodium thiolate complex catalysts Rh−S/SiO2 and Rh−S−P/SiO2 were prepared by the condensation of SiO2 with Rh2[μ-S(CH2)3Si(OCH3)3]2(CO)4 (Rh−S) or Rh2[μ-S(CH2)3Si(OCH3)3]2[Ph2P(CH2)3Si(OC2H5)3]2(CO)2 (Rh−S−P). These tethered complex catalysts exhibit high activity for the hydroformylation of 1-octene in the presence of phosphine donor ligands under the mild conditions of 60 °C and 1 atm. IR (DRIFT) spectral studies of the catalysts used indicate that tethered monorhodium dicarbonyl thiolate complexes of the type Rh(SR)(CO)2(PR‘3) are the predominant species on the surface for the catalysts that have the highest hydroformylation activity. The catalysts are easily separated from the reaction mixtures, and the Rh−S/SiO2 catalyst maintains its activity through at least three cycles over a total period of 69 h, during which time there are 1273 (mol of aldehyde/mol of Rh) turnovers. Effects of the phosphine ligand and PR‘3/Rh mole ratio on the hydroformylation rate, conversion, and chemo- and regioselectivity for aldehyde products were also investigated.