RARE-EARTH-METAL INITIATED LIVING POLYMER IZATIONS OF POLAR AND NONPOLAR MONOMERS

A nonmetallocene-type rare earth metal complex, [(SiMe3)(3)C](2)Yb, wa s found to proceed the isotactic polymerization of methyl methacrylate (MMA) to give a high molecular weight polymer with narrow molecular w eight 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, (C3Me3)La[CH(SiMe3)(2)](2), proceeds th e polymerization of styrene, alkyl isocyanates, acrylonitrile, and eth ylene. Furthermore, rare earth metal complexes exhibiting one cyclopen tadienyl group and one acetylene group or benzyl group also showed rel atively large catalytic activity for the polymerization of ethylene. A novel triphenyl complex, (2,6-alkoxy C6H3)(3)Sm, was also prepared bu t this complex showed very weak catalytic activity towards the polymer ization of ethylene.