Light induced addition of diphenylphosphine (DPP) to methylvinylcyclotetrasiloxane (MVS) yielded poly(2-diphenylphosphinoethyl) cyclotetrasiloxane (DPPS). Similar treatment of allyldiphenylphosphine (ADPP) with linear poly(methylhydrogenosiloxane)-co-hexamethyldisiloxane (PMS) led to formation of poly(3-diphenylphosphinopropyl)methylsiloxane-co-hexamethyldisiloxane (PPMS). DPPS and PPMS were condensed by acid treatment to give insoluble rubbery phosphine bearing materials P1 and P2, respectively. Iridium and rhodium complexes were immobilized on P1 and P2. The ability of a high molecular weight substrate (PMS) to migrate to active catalytic centers within support matrix was examined. The effect of varying metal: phosphine ratio and total percentage metal on the support were examined during catalysis of O-silylation of ethanol with PMS and triethoxysilane (TES).