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

4个非桥联和5个二甲基硅烯桥联的二甲基锆，即bis(eta^5-cyclopentadienyl)dimethylzirconium(1)，(eta^5-cyclopentadieny)(eta^5-fluorenyl)dimethylzirconium(2)，双(eta^5-吲基)二甲基锆(3)，(eta^5-cyclopentadieny)(eta^5-pentamethylcyclo-戊二烯)二甲基锆(4)，二甲基硅烯双(eta^5-环戊二烯基)二甲基1，dimethylsilylene(eta^5-cyclopentadienyl)(eta^5-fluorenyl)dimethylzirconium(6)，rac-dimethylsilylenebis(eta^5-cyclopentadienyl)dimethylzirconium(7)，合成了meso-dimethylsilylenebis(eta^5-cyclopentadienyl)dimethylzirconium(8)和dimethylsilylene(eta^5-cyclopentadienyl)(eta^5-indenyl)dimethylzirconium(9)，并将其用于催化甲基丙烯酸甲酯与triphenylmethyltetrakis(pentafluorophenyl)borate或N，N-dimethylpyridinyltetrakis(pentafluorophenyl)borate在ZNet_2或Al(i-Bu)_3存在下的聚合反应。催化剂的活性强烈依赖于茂锆族化合物，降低了I-…更多按以下顺序排列；2&gt；1&gt；7&gt；5&gt；9&gt；3&gt；&gt；4、6、8=0。当1和2与ZNET_2结合时，聚合反应以活泼的方式进行。用非桥联的锆烯得到的聚合物的立构规整性与环戊二烯配体无关，间同立构聚合物是由链端控制的机理形成的。硅烯桥联的锆烯化合物的立体专一性强烈依赖于它们的对称性。C&lt；2v&gt；对称型5得到了与非桥联锆烯类似的富间同立构聚合物，而C2-对称型7和C_1-对称型9通过对映位控制机制得到了高度全同立构的聚合物。这些催化剂体系对甲基丙烯酸烯丙酯聚合也具有催化活性，得到带有侧链的烯丙基酯聚合物。聚合物的立体规整性与聚甲基丙烯酸甲酯相同，可以通过所用的茂锆化合物进行控制。甲基丙烯酸烯丙酯与甲基丙烯酸甲酯的无规共聚合也得到了含烯丙基酯基团的聚甲基丙烯酸甲酯，其含量易受投料比的控制。较少

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