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

四个非桥连的和五个二甲基亚甲硅烷基桥连的茂锆二甲基，即，双（η-5-二甲基）锆（1），（η ^5-环戊二烯基）（η ^5-芴基）二甲基锆（2），双（η-5-茚基）二甲基锆（3），（η ^5-环戊二烯基）（η ^5-五甲基环戊二烯基）二甲基锆（4），二甲基亚甲硅烷基双（eta^5-正）二甲基锆（5），二甲基亚甲硅烷基（η ^5-π）（η ^5-芴基）二甲基锆（6），外消旋-二甲基亚甲硅烷基双（η-4，5-二甲基）二甲基锆（7），meso-二甲基亚硅基双（η ^5-ε）二甲基锆（8）和二甲基亚甲硅烷基（η ^5-π）合成了（η ^5-茚基）二甲基锆（9），并将其用作甲基丙烯酸甲酯聚合的催化剂，在ZnEt_2或Al（i-Bu）_3存在下，茂锆化合物的催化活性对茂锆化合物有很强的依赖性，茂锆化合物的存在会降低茂锆化合物的催化活性。 关于我们 按以下顺序; 2> 1 > 7 > 5 > 9 > 3 >> 4，6，8 = 0。当1和2与ZnEt_2结合使用时，聚合以活性方式进行。与非桥的二茂锆得到的聚合物的立构规整性是独立的的双金属配体，和间同立构丰富的聚合物形成的链端控制的机制。硅桥连的二茂锆的立体专一性强烈地依赖于它们的对称性。C_2<2v>-对称的5和C_1-对称的9通过对映异构体控制的机理得到了高度全同立构的聚合物，而C_2-对称的7和C_1-对称的9则得到了与非桥连的茂锆类似的富间同立构的聚合物，这些催化剂体系对甲基丙烯酸烯丙酯的聚合也具有活性。聚合物的立构规整性与聚甲基丙烯酸甲酯相同，这可以通过所使用的茂锆化合物来控制。甲基丙烯酸烯丙酯和甲基丙烯酸甲酯的无规共聚也进行生产聚（甲基丙烯酸甲酯）与侧链烯丙基酯基团，其含量很容易控制的进料比。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