Rare earth metal-initiated living polymerizations of polar and nonpolar monomers

Abstract

A nonmetallocene-type rare earth metal complex, [(SiMe3)SC]2Yb, was found to proceed the isotactic polymerization of methyl methacrylate (MMA) to give a high molecular weight polymer with narrow molecular weight distribution. We can synthesize stereo-complexes of poly(MMA) by mixing the resulting isotactic polymer with the high molecular weight syndiotactic poly(MMA) synthesized with SmH(C5Me5)2. Half-sandwich type rare earth metal complex, (C5Me5)La[CH(SiMe3)2]2, proceeds the polymerization of styrene, alkyl isocyanates, acrylonitrile, and ethylene. Furthermore, rare earth metal complexes exhibiting one cyclopentadienyl group and one acetylene group or benzyl group also showed relatively large catalytic activity for the polymerization of ethylene. A novel triphenyl complex, (2,6-alkoxy C6H3)3Sm, was also prepared but this complex showed very weak catalytic activity towards the polymerization of ethylene.