Synthesis and characterization of the titanium complexes bearing two regioisomeric trifluoromethyl-containing enaminoketonato ligands and their behavior in ethylene polymerization
作者:Wei-Ping Ye、Hong-Liang Mu、Xin-Cui Shi、Yan-Xiang Cheng、Yue-Sheng Li
DOI:10.1039/b906854f
日期:——
A series of new titanium complexes bearing two regioisomeric trifluoromethyl-containing enaminoketonato ligands (3a–h and 6a–h), [PhNCRCHC(CF3)O]2TiCl2 (3a, R = Me; 3b, R = n-C5H11; 3c, R = i-Pr; 3d, R = Cy; 3e, R = t-Bu; 3f, R = CHCHPh; 3g, R = Et; 3h, R = n-C11H23) and [PhNC(CF3)CHC(R)O]2TiCl2 (6a, R = Ph; 6b, R = n-C5H11; 6c, R = i-Pr; 6d, R = Cy; 6e, R = t–Bu; 6f, R = CHCHPh; 6g, R = CHPh2; 6h, R = CF3) have been synthesized and characterized. X-ray crystal structures analyses suggest that complexes 3c–e and 6c–d all adopt a distorted octahedral geometry around the titanium center. Complexes 3c, 3d and 6c display a cis-configuration of the two chlorine atoms around the titanium center, while complex 6d shows a trans-configuration of the two chlorine atoms. Especially, the configurational isomers (cis and trans) of complex 3e were identified both in solution and in the solid state by NMR and X-ray analyses. With modified methylaluminoxane as a cocatalyst, all the complexes are active towards ethylene polymerization, and produce high molecular weight polymers. With the variation of the relative position of the imino group and the trifluoromethyl group of the β-enaminoketonato ligands, the polymerization behavior of the catalysts changed remarkably. It is observed that the substituent directly joined to the carbonyl in the ligands plays an important role for both the catalytic activities and the properties of the polymers produced.
一系列含有两个位异构的三氟甲基取代烯胺酮配体的新型钛配合物(3a-h和6a-h),[PhNCRCHC(CF3)O]2TiCl2(3a,R = Me;3b,R = n-C5H11;3c,R = i-Pr;3d,R = Cy;3e,R = t-Bu;3f,R = CHCHPh;3g,R = Et;3h,R = n-C11H23)和[PhNC(CF3)CHC(R)O]2TiCl2(6a,R = Ph;6b,R = n-C5H11;6c,R = i-Pr;6d,R = Cy;6e,R = t-Bu;6f,R = CHCHPh;6g,R = CHPh2;6h,R = CF3)已被合成并表征。X射线晶体结构分析表明,配合物3c-e和6c-d在钛中心周围均采取扭曲的八面体几何构型。配合物3c、3d和6c在钛中心周围显示出两个氯原子的顺式构型,而配合物6d显示出两个氯原子的反式构型。特别是,通过NMR和X射线分析在溶液和固态中都确定了配合物3e的构型异构体(顺式和反式)。以改性甲基铝氧烷为共催化剂,所有配合物均对乙烯聚合活性良好,并生成高分子量聚合物。随着β-烯胺酮配体中亚胺基和三氟甲基相对位置的变化,催化剂的聚合行为发生了显著变化。观察到,直接连接到配体中羰基上的取代基对于催化活性和所生成聚合物的性质起着重要作用。