Ethylene Polymerization Catalyzed by Monocyclopentadienyl Titanium Complex Containing 8-Quinolinolato Ligand and ADF Study on the Formation Mechanism of Active Species

A monocyclopentadienyl titanium complex containing 8-quinolinolato (QCpTiCl_2) was synthesized. Its activities in ethylene polymerization at various Al/Ti molar ratios, different temperatures and activation time were investigated. The activity with a Al/Ti molar ratio of 500 exhibited a maximum of 2.8×10~5 g/(mol.h) at 30℃. The activation time of QCpTiCl_2 with MAO before polymerization also plays a role on the activity. The structural properties of the produced polyethylene (molecular weight, molecular weight distribution and melting point) were discussed. Kinetic behaviors of ethylene polymerization with the QCpTiCl_2/MAO system at different Al/Ti molar ratios were studied. For the QCpTiMeCl/MAO system and the CpTiMe_2Cl/MAO system, binding energies of the examined intermediates were calculated by quantum-mechanical method based on ADF program, respectively. It is confirmed that the chlorinebridged adduct formed by the reaction of QCpTiMeCl with MAO is thermodynamically steady. In the case of the QCpTiMeCl/MAO system, olefin-separated ion pair (OSIP) mechanism is much favorable than ion-pair dissociation (IPD) mechanism. The experimental result on the CpTiMe_2Cl/MAO system showed lower activity for ethylene polymerization than that on the QCpTiMeCl/MAO system, which revealed that the CpTiMe_2Cl/MAO system is unfavorable to form active species with ethylene.

四甲基环戊二烯基苯氧基二氯化钛衍生物的合成及催化烯烃聚合研究

4-R1 -6-R-2 -Me4 Cp H-Ph OH[R1 =t Bu,R=t Bu(1 ) ;R1 =H,R=t Bu(2 ) ,Ph(3 ) ,Me(4 ) ]经双三甲基硅基化后与 Ti Cl4 反应 ,合成了 4种限制几何构型茂金属催化剂 4-R1 -6-R-2 -Me4 Cp-Ph OTi Cl2 [R1 =t Bu,R=t Bu(5 ) ;R1 =H,R=t Bu(6) ,Ph(7) ,Me(8) ],合成产率有较大提高 .这些茂金属化合物经过 i Bu3Al和Ph3C+ B(C6 F5) - 4活化后对乙烯聚合有很好的催化活性 ,并生成乙基支化聚乙烯 .考察了催化剂结构与活性的关系以及聚合反应条件对催化剂性能的影响 。