Synthesis, structures and ethylene polymerization behavior of half-metallocene chromium(iii) catalysts bearing salicylaldiminato ligands
作者:Mingtai Sun、Ying Mu、Qiaolin Wu、Wei Gao、Ling Ye
DOI:10.1039/c0nj00439a
日期:——
A series of half-metallocene chromium(III) complexes bearing a salicylaldiminato ligand, Cp′[2-R1-4-R2-6-(CH = NR3)C6H2O]CrCl [Cp′ = Cp (1, 5), Cp* (2, 3, 4, 6, 7, 8); R1 = Ph (1, 2, 3, 5, 6, 8), iPr (4), tBu (7); R2 = H (1, 2, 3), Br (4), NO2 (5, 6, 7, 8); R3 = iPr (1, 2, 5, 6, 7), tBu (3, 4, 8)], were synthesized. The structures of complexes 1, 3–5, 7–8 were determined by single crystal X-ray diffraction analysis. The X-ray crystallographic analysis indicates that these complexes adopt a pseudo-octahedral coordination environment with a three-legged piano stool geometry. Upon activation with a small amount of AlEt3, complexes 1–8 exhibit good to high catalytic activity for ethylene polymerization and produce ultra-high molecular weight polyethylene (PE) under mild conditions. The productivity of these complexes is relatively low when activated with AlMe3 and AliBu3. Both the productivity of these catalyst systems and the molecular weight of the produced PE can be tuned in a broad range by changing the ligands and the AlR3 co-catalyst.
一系列含水杨醛配体的半茂金属铬(III)配合物,Cp′[2-R1-4-R2-6-(CH = NR3)C6H2O]CrCl [Cp′ = Cp (1, 5), Cp* (2, 3, 4, 6, 7, 8);R1 = Ph (1, 2, 3, 5, 6, 8),iPr (4),tBu (7);R2 = H (1, 2, 3),Br (4),NO2 (5, 6, 7, 8);R3 = iPr (1, 2, 5, 6, 7),tBu (3, 4, 8)]。通过单晶 X 射线衍射分析确定了复合物 1、3-5、7-8 的结构。X 射线晶体分析表明,这些配合物采用了三脚钢琴凳几何形状的假八面体配位环境。用少量 AlEt3 活化后,1-8 复合物对乙烯聚合具有很好甚至很高的催化活性,并能在温和的条件下生成超高分子量聚乙烯(PE)。当用 AlMe3 和 AliBu3 活化时,这些配合物的生产率相对较低。通过改变配体和 AlR3 助催化剂,可以在很大范围内调整这些催化剂体系的生产率和生成的聚乙烯的分子量。