The George and Josephine Butler Laboratory for Polymer Research, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, USA.
Dalton Trans. 2013 Jul 7;42(25):9139-47. doi: 10.1039/c3dt50163a. Epub 2013 Mar 13.
Several analogues of the sterically expanded constrained geometry catalyst Me2Si(η(1)-C29H36)(η(1)-N-tBu)ZrCl2·OEt2 (2) were synthesized to assess the effect on branching and molecular weight for ethylene homopolymerization. Catalysts based on tetramethyltetrahydrobenzofluorene (TetH), ethylTetH, t-butylTetH, and octamethyloctahydrodibenzofluorenyl (OctH) bearing a diphenylsilyl bridge were prepared and characterized: Me2Si(η(5)-C21H22)(η(1)-N-tBu)ZrCl2 (3); Me2Si(η(5)-C23H26)(η(1)-N-tBu)ZrCl2 (4); and Me2Si(η(5)-C25H30)(η(1)-N-tBu)ZrCl2 (5); Me2Si(η(5)-C21H22)(η(1)-N-tBu)ZrMe2 (6); and Ph2Si(η(5)-C29H36)(η(1)-N-tBu)ZrCl2 (7). Complexes 4, 5, 6, and 7 were characterized by X-ray crystallography and displayed η(5) hapticity to the carbon ring in each case, in contrast to 2. In comparison to 2, complexes 3, 4, 5, and 7 (in combination with methylaluminoxane = MAO) showed diminished branching, higher molecular weight, and higher polydispersity indices for obtained ethylene homopolymers. While 4/MAO produced the greatest molecular weight polymers, no branching was observed. Reactivity ratios were determined for the copolymerization of ethylene and 1-decene with 2/MAO. A value of r(ethylene) = 14.9 and an exceedingly high value of r(1-decene) = 0.49 were found--in line with previous reports of this catalyst's unusual affinity for α-olefins.
几种立体扩展约束几何催化剂 Me2Si(η(1)-C29H36)(η(1)-N-tBu)ZrCl2·OEt2（2）的类似物被合成，以评估其对乙烯均聚物支化和分子量的影响。基于四甲基四氢苯并[F]茚（TetH）、乙基 TetH、叔丁基 TetH 和八甲氧基八氢二苯并[F]茚（OctH）的带有二苯基硅桥的催化剂被制备和表征：Me2Si(η(5)-C21H22)(η(1)-N-tBu)ZrCl2（3）；Me2Si(η(5)-C23H26)(η(1)-N-tBu)ZrCl2（4）；和 Me2Si(η(5)-C25H30)(η(1)-N-tBu)ZrCl2（5）；Me2Si(η(5)-C21H22)(η(1)-N-tBu)ZrMe2（6）；和 Ph2Si(η(5)-C29H36)(η(1)-N-tBu)ZrCl2（7）。配合物 4、5、6 和 7 通过 X 射线晶体学进行了表征，并且在每种情况下都显示出对碳环的 η(5)配位性，与 2 形成对比。与 2 相比，配合物 3、4、5 和 7（与甲基铝氧烷=MAO 结合）显示出降低的支化度、更高的分子量和更高的获得的乙烯均聚物的多分散指数。虽然 4/MAO 生产出分子量最高的聚合物，但没有观察到支化。使用 2/MAO 测定了乙烯和 1-癸烯的共聚反应的竞聚率。发现 r(ethylene)=14.9 和 r(1-decene)的极高值 0.49——与该催化剂对α-烯烃异常亲和力的先前报道一致。
