作者:Sze-Man Yu、Ulrich Tritschler、Inigo Göttker-Schnetmann、Stefan Mecking
DOI:10.1039/b916289e
日期:——
Zirconium complexes with enolatoimine ligands bearing an electron-withdrawing trifluoromethyl group on the alkoxy moiety [κ2-N,O-2,6-R2NC(CH3)C(H)C(O)CF3]2ZrCl2 (2a, R = H; 2b, R = F; 2c, R = CH3; 2d, R = iPr) were prepared. The isopropyl substituents hinder rotation in solution for 2d, and result in a trans-arrangement of the N-donors in the solid state. Catalyst activities are similar for 2a/MAO and 2b/MAO in ethylene polymerization (1.8 × 105 TO h−1 for 2a and 3.3 × 105 TO h−1 for 2b at 25 °C under 1 bar monomer pressure), increasingly bulky alkyl substituents result in strongly decreased polymerization activities (7.1 × 102 TO h−1 for 2c and 5.7 × 102 TO h−1 for 2d at 25 °C). This goes along with an increase in polymer molecular weight (Mw = 8.1 × 103, Mw/Mn = 2.9 for 2a, Mw = 3.8 × 105, Mw/Mn = 2.0 for 2b, Mw = 1.0 × 106, Mw/Mn = 2.8 for 2c), apparently bulky substituents retard chain transfer even more strongly than activation of the precursors and/or chain growth. 2b/MAO affords atactic polypropylene (Mw = 1.4 × 104 g mol−1, Mw/Mn = 2.1) with a small portion of regioirregular structures. The reaction of [Zr(CH2Ph)4] with the ketoenamine 2,6-F2C6H3N(H)CMeCHC(O)CF3 (1b) yielded the dibenzyl complex [(o-F2C6H3NCMeCHC(CF3)O)2Zr(CH2Ph)2] (3b) which was investigated as a catalyst precursor for ethylene homopolymerization in combination with different activators.
带有烯醇亚胺配体的锆配合物,烷氧基部分上带有吸电子三氟甲基基团 [κ2-N,O-2,6-R2NC(CH3)C(H)C(O)CF3]2ZrCl2 (2a, R = H;制备了2b,R=F;2c,R=CH3;2d,R=iPr)。异丙基取代基在溶液中阻碍旋转 2d,并导致固态 N-供体发生反式排列。乙烯聚合中 2a/MAO 和 2b/MAO 的催化剂活性相似(2a 为 1.8 × 105 TO h−1,2b 为 3.3 × 105 TO h−1,在 25 °C、1 bar 单体压力下),烷基取代基越来越大导致聚合活性大大降低(2c 为 7.1 × 102 TO h−1,2c 为 5.7 × 102 TO h−1) h−1 在 25 °C 下持续 2d)。这伴随着聚合物分子量的增加(2a的Mw = 8.1 × 103,Mw/Mn = 2.9,Mw = 3.8 × 105,2b的Mw/Mn = 2.0,Mw = 1.0 × 106,Mw/Mn = 2.8对于2c),明显庞大的取代基比前体和/或链的活化更强烈地阻碍链转移 生长。 2b/MAO 提供具有一小部分区域不规则结构的无规聚丙烯(Mw = 1.4 × 104 g mol−1,Mw/Mn = 2.1)。 [Zr(CH2Ph)4] 与酮烯胺 2,6-F2C6H3N(H)CMeCHC(O)CF3 (1b) 反应生成二苄基络合物 [(o-F2C6H3NCMeCHC(CF3)O)2Zr(CH2Ph)2] ( 3b)将其与不同的活化剂结合作为乙烯均聚的催化剂前体进行研究。