Highly stereospecific polymerization of polar vinyl monomers by group-4 metallocene catalysts

四种非桥接和五种二甲基硅氧烷桥接的锆新二甲基，即二（eta^5-环戊二烯基）二甲基锆(1)、（eta^5-环戊二烯基）（eta^5-氟二烯基）二甲基锆(2)、二（eta^5-环戊二烯基）二甲基锆(3)、（eta^5-环戊二烯基）二甲基锆(4)、二甲基硅氧烷（eta^5-环戊二烯基）二甲基锆(5)、二甲基硅氧烷（eta^5-环戊二烯基）二甲基锆(6)、在ZnEt_2或Al(i-Bu)_3存在下，合成了rac-二甲基硅基双（eta^5-环戊二烯基）二甲基锆(7)、中-二甲基硅基双（eta^5-环戊二烯基）二甲基锆(8)和二甲基硅基（eta^5-环戊二烯基）二甲基锆(9)，并与三苯基甲基四（五氟苯）硼酸盐或N，N-二甲基吡啶基四（五氟苯）硼酸盐结合，作为甲基丙烯酸甲酯聚合的催化剂。催化剂活性强烈依赖于锆新世化合物，并依次降低；2> 1 > 7 > 5 > 9 > 3 >> 4,6,8 = 0。当1和2与ZnEt_2结合使用时，聚合反应进行得很顺利。非桥接锆茂烯聚合物的立体规整性与环戊二烯基配体无关，并通过链端控制机制形成富共规性聚合物。硅烷桥接锆石的立体专一性主要取决于它们的对称性。C_<2v>-对称5得到与非桥接锆石相似的富同规性聚合物，而c_2 -对称7和c_1 -对称9通过对构位控制机制得到高度等规性聚合物。这些催化剂体系对甲基丙烯酸烯丙酯的聚合也有活性，从而得到带有垂坠烯丙酯基团的聚合物。聚合物的立体规整性与聚甲基丙烯酸甲酯相同，这可以通过采用锆新统化合物来控制。甲基丙烯酸烯丙酯与甲基丙烯酸甲酯的无规共聚也可得到烯丙酯基团悬垂的聚甲基丙烯酸甲酯，其含量易受投料比控制。少

Four non-bridged and five dimethylsilylene-bridged zirconocenedimethyls, i.e., bis(eta^5-cyclopentadienyl)dimethylzirconium(1), (eta^5-cyclopentadieny)(eta^5-fluorenyl)dimethylzirconium(2), bis(eta^5-indenyl)dimetliylzirconium(3), (eta^5-cyclopentadieny)(eta^5-pentamethylcyclo- pentadieny)dimethylzirconium(4), dimethylsilylenebis (eta^5-cyclopentadienyl)dimethy1zirconium(5), dimethylsilylene(eta^5-cyclopentadienyl)(eta^5-fluorenyl)dimethylzirconium(6), rac-dimethylsilylenebis(eta^5-cyclopentadienyl)dimethylzirconium(7), meso-dimethylsilylenebis(eta^5-cyclopentadienyl)dimethylzirconium(8) and dimethylsilylene(eta^5-cyclopentadienyl)(eta^5-indenyl)dimethylzirconium (9) were synthesized and used as a catalyst for methyl methacrylate polymerization combined with triphenylmethyltetrakis(pentafluorophenyl)borate or N,N-dimethylpyridinyltetrakis(pentafluorophenyl)borate in the presence of ZnEt_2 or Al(i-Bu)_3.The catalyst activity strongly depended on the zirconocene compounds and decreased i … More n the following order ; 2> 1 > 7 > 5 > 9 > 3 >> 4, 6, 8 = 0. The polymerization proceeded in a living manner when 1 and 2 were used combined with ZnEt_2. The stereoregularity of the polymers obtained with the non-bridged zirconocenes were independent of the cyclopentadienyl ligands, and syndiotactic-rich polymers were formed by a chain-end controlled mechanism. The stereospecificity of the silylene-bridged zirconocenes were strongly depended on their symmetries. C_<2v>-symmetric 5 gave a syndiotactic-rich polymer similarly to the non-bridged zirconocenes, while C_2-symmetric 7 and C_1-symmetric 9 gave highly isotactic polymers by a enantiomorphic-site controlled mechamsm.These catalyst systems are also active for polymerization of allyl methacrylate to give polymers with pendant allyl-ester groups. The stereoregularity of the polymers were the same with poly(methyl methacrylate), which could be controlled by the zirconocene compounds employed. Random copolymerization of allyl methacrylate and methyl methacrylate also proceeded to produce poly(methyl methacrylate) with pendant allyl-ester groups, of which content was easily controlled by the feed ratio. Less