Large ultra-high molecular weight polyethylene spherical particles produced by AlR3 activated half-sandwich chromium(iii) catalysts
作者:Mingtai Sun、Tieqi Xu、Wei Gao、Yang Liu、Qiaolin Wu、Ying Mu、Ling Ye
DOI:10.1039/c1dt10659g
日期:——
A series of half-sandwich pentamethylcyclopentadienyl chromium(III) complexes bearing a salicylaldiminato ligand, Cp*[2-R1-4-R2-6-(CHNR3)C6H2O]CrCl [R1 = iPr (1, 4), tBu (2, 3, 5), Ad (6); R2 = H (1, 2, 3), tBu (4, 5, 6); R3 = iPr (1, 2, 5, 6), tBu (3, 4)], were synthesized. All complexes were characterized by elemental analyses and the structures of complexes 1–4 and 6 were determined by X-ray diffraction analysis. These complexes adopt a pseudo-octahedral coordination environment with a three-legged piano stool geometry. Upon activation with a small amount of AlR3, complexes 1–6 all catalyze the polymerization of ethylene in a quasi living fashion with good to high catalytic activity under mild conditions and produce ultra-high molecular weight polyethylene as spherical particles with a diameter of 1–6 mm. The catalytic activity of these complexes and the molecular weight of the produced polyethylene can be tuned in a broad range by changing the R1, R2, and R3groups as well as the AlR3 cocatalyst. It was found that complex 6 with R1 = Ad, R2 = tBu, and R3 = iPr shows the highest catalytic activity and produces polyethylene with the highest molecular weight.
合成了一系列半夹心的五甲基环戊二烯铬(III)配合物,该配合物具有水杨醛亚胺配体,Cp*[2-R1-4-R2-6-(CHNR3)C6H2O]CrCl [R1 = iPr (1, 4), tBu (2, 3, 5), Ad (6); R2 = H (1, 2, 3), tBu (4, 5, 6); R3 = iPr (1, 2, 5, 6), tBu (3, 4)]。所有配合物均通过元素分析进行表征,配合物1–4和6的结构通过X射线衍射分析确定。这些配合物采用伪八面体配位环境,具有三脚钢琴凳几何结构。在激活AlR3少量的情况下,配合物1–6均能以近生的方式催化乙烯聚合,在温和条件下表现出良好至高的催化活性,产生直径为1–6毫米的超高分子量聚乙烯球形颗粒。通过改变R1、R2、R3基团以及AlR3助催化剂,可以在宽范围内调节这些配合物的催化活性和所生成聚乙烯的分子量。发现配合物6(R1 = Ad, R2 = tBu, R3 = iPr)具有最高的催化活性,并生成具有最高分子量的聚乙烯。