State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, China.
Dalton Trans. 2010 Oct 14;39(38):9000-7. doi: 10.1039/c001987a. Epub 2010 Aug 18.
A series of new titanium complexes with two asymmetric bidentate β-enaminoketonato [N,O] ligands (2b-t), PhN=C(CF(3))CHC(Ar)OTiCl(2) (2b, Ar = -C(6)H(4)F(o); 2c, Ar = -C(6)H(4)F(m); 2d, Ar = -C(6)H(4)F(p); 2e, Ar = -C(6)H(4)Cl(p); 2f, Ar = -C(6)H(4)OMe(p); 2g, Ar = -C(6)H(4)CF(3)(p); 2h, Ar = -C(6)H(4)CF(3)(m); 2i, Ar = -C(6)H(4)CF(3)(o); 2j, Ar = -C(6)H(4)Cl(o); 2k, Ar = -C(6)H(4)Br(o); 2l, Ar = -C(6)H(4)I(o); 2m, Ar = -C(6)H(3)F(2)(2,4); 2n, Ar = -C(6)H(3)F(2)(2,6); 2o, Ar = -C(6)H(3)F(2)(3,4); 2p, Ar = -C(6)H(3)F(2)(3,5); 2q, Ar = -C(6)F(5); 2r, Ar = C(6)F(4)OMe; 2s, Ar = -C(6)H(3)Cl(2)(2,6); 2t, Ar = -C(6)H(3)Cl(2)(2,5)), have been synthesized based on substituted acetophenones. X-Ray analyses reveal that complexes 2h, 2k, 2m, and 2n adopt distorted octahedral geometry around the titanium center, in which the two chloride ligands are situated in the cis-orientation. 2s also adopts distorted octahedral geometry, but the two chloride ligands in it are situated in the trans-orientation due to the increase of the steric effect of the phenyl derived from the acetophenone. The influence of the substituent effects on catalyst performance, including catalytic activities and the molecular weight distribution of the polymers obtained, was investigated in detail. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 2b-r and 2t are active catalysts for ethylene polymerization at room temperature, and produce high molecular weight polymers. It is observed that the catalytic activities are significantly enhanced by introducing some electron-withdrawing groups, such as -F, -Cl and -CF(3), into the suitable positions of the phenyl ring close to the oxygen donor. It should be noted that complexes 2c-i, 2p, 2n and 2t are also capable of promoting the living copolymerization of ethylene with norbornene at room temperature, yielding high molecular weight copolymers with narrow molecular weight distributions (PDI = 1.05-1.30).
一系列新的钛配合物，具有两个不对称的双齿β-烯胺酮[氮，氧]配体（2b-t），[PhN = C（CF 3 ）CHC（Ar）O]（2）TiCl 2 （2b，Ar = -C （6 ）H （4 ）F（o）; 2c，Ar = -C （6 ）H （4 ）F（m）; 2d，Ar = -C （6 ）H （4 ）F（p）; 2e，Ar = -C （6 ）H （4 ）Cl（p）; 2f，Ar = -C （6 ）H （4 ）MeO（p）; 2g，Ar = -C （6 ）H （4 ）CF 3 （p）; 2h，Ar = -C （6 ）H （4 ）CF 3 （m）; 2i，Ar = -C （6 ）H （4 ）CF 3 （o）; 2j，Ar = -C （6 ）H （4 ）Cl（o）; 2k，Ar = -C （6 ）H （4 ）Br（o）; 2l，Ar = -C （6 ）H （4 ）I（o）; 2m，Ar = -C （6 ）H （3 ）F 2 （2,4）; 2n，Ar = -C （6 ）H （3 ）F 2 （2,6）; 2o，Ar = -C （6 ）H （3 ）F 2 （3,4）; 2p，Ar = -C （6 ）H （3 ）F 2 （3,5）; 2q，Ar = -C （6 ）F 5 ； 2r，Ar = C （6 ）F 4 甲氧基; 2s，Ar = -C （6 ）H （3 ）Cl 2 （2,6）; 2t，Ar = -C （6 ）H （3 ）Cl 2 （2,5）），已经基于取代的苯乙酮合成。X射线分析表明，配合物 2h，2k，2m和 2n在钛中心周围采用扭曲的八面体几何形状，其中两个氯配体位于顺式取向。2s也采用扭曲的八面体几何形状，但是由于苯乙酮衍生的苯基的空间位阻增加，其中的两个氯配体位于反式取向。研究了取代基效应对催化剂性能的影响，包括催化剂的催化活性和获得的聚合物的分子量分布。用改性甲基铝氧烷（MMAO）作为助催化剂，配合物 2b-r和 2t是在室温下用于乙烯聚合的活性催化剂，并产生高分子量聚合物。观察到通过在靠近供体氧的苯基的适当位置引入一些吸电子基团，例如-F，-Cl和-CF 3 ，可以显著提高催化活性。应当注意的是，配合物 2c-i，2p，2n和 2t也能够在室温下促进乙烯与降冰片烯的共聚，得到具有窄分子量分布（PDI = 1.05-1.30）的高分子量共聚物。
