Triethoxysilyl substituted diphosphines of the novel type (EtO)
3Si(CH
2)
nP(Ph)CH
2CH
2PPh
2 (n=1, 3) have been prepared and used to immobilize rhodium(I) complexes to silica. The complexes were found to be effective catalysts for hydrogenation of 1,3-cyclooctadiene under mild conditions.