Polymerization of New Metallocenylphosphazenes

The polymerization behavior has been examined of four cyclophosphazenes that are bridged by transannular metallocenyl groups. It was found that two ferrocenyl units, one transannular and one pendent, do not block the polymerization process of a fluorocyclotriphosphazene, even though the trimer with only one pendent ferrocenyl group cannot be polymerized. Release of phosphazene ring strain induced by the transannular component appears to be responsible for the difference. A 1,5-transannular ferrocenyl or ruthenocenyl group has a lesser influence on the polymerizability of a phosphazene cyclic tetrameric ring. No evidence was found for a redistribution of monomer units in the conversion of the cyclic oligomers to polymers.