A Simple Access to Highly Active Heterogeneous Hydrogenation Catalysts

This paper describes the synthesis, characterization and application in hydrogenation catalysis of triphenylphosphine-stabilized palladium and rhodium species on SBA-15. The materials were achieved by synthesizing a triethoxysilyl-functionalized triphenylphosphine ligand through the reaction of (2-chloromethylphenyl)diphenylphosphine and (3-mercaptopropyl)triethoxysilane. Treatment of this ligand with the appropriate palladium(II) and rhodium(I) complexes produced the corresponding transition metal complexes, which were then immobilized on the support material. The final catalysts were obtained by treating these precursor materials with dihydrogen at elevated temperatures. These catalysts are highly active in the hydrogenation of a wide range of olefins under mild conditions. XPS studies on one of the palladium catalysts reveal that only a part of the metal is reduced, with almost no further reduction of the remaining palladium(II) species observed after tenfold recycling and reuse of the material.