New rhodium complexes anchored on silica and modified Y-zeolite as efficient catalysts for hydrogenation of olefins

New rhodium complexes of formula [RhCl(COD)L], [RhCl(CO)2L], [Rh(PPh3)2L] and the corresponding cationic ones, where L = 2-(3-triethoxysilylpropyl)aminocarbonyl-pyrrolidine, have been covalently bound to silica and ultrastable Y-zeolite containing supermicropores. The complexes anchored on the zeolite show a higher activity for alkene hydrogenation than the free complexes in homogeneous medium, the silica-anchored catalysts being the least active. No loss in hydrogenation activity was observed with the complexes immobilized on zeolite after ten recycles, and the leaching of metal was not appreciable; thus they represent a truly heterogeneous counterpart to homogeneous transition metal complex catalysts.