2-Benzimidazolyl-N-phenylquinoline-8-carboxamide Chromium(III) Trichlorides: Synthesis and Application for Ethylene Oligomerization and Polymerization

A series of chromium(III) complexes, LCrCl3 (C1–C6: L = 2-(1H-benzo[d]imidazol-2-yl)-N-(2,6-R1-4-R2-phenyl)quinoline-8-carboxamide; C1: R1 = iPr, R2 = H; C2: R1 = Et, R2 = H; C3: R1 = Me, R2 = H; C4: R1 = Me, R2 = Me; C5: R1 = H, R2 = H; C6: R1 = F, R2 = H), was synthesized and characterized by IR spectroscopy, elemental analysis, mass spectra, and magnetic moments. The X-ray crystallographic analysis of complexes C2 and C3 reveals distorted octahedral geometries around the chromium atoms. Upon activation with MAO, these complexes exhibit high activities for ethylene oligomerization (up to 1.28 × 107 g·mol–1(Cr)·h–1) and ethylene polymerization (up to 6.30 × 106 g·mol–1(Cr)·h–1). The oligomers were produced with high selectivity for α-olefins (>99%), and the distribution closely resembled the Schultz–Flory rule. Various reaction parameters were investigated in detail, and the results revealed that both the steric and electronic effects of the ligands effect the catalytic activities of these chromium complexes as well as the distribution of the products formed.

一系列铬(III)络合物，包括LCrCl3（C1–C6：L = 2-(1H-苯并[d]咪唑-2-基)-N-(2,6-取代基-4-取代基苯基)喹啉-8-甲酰胺；C1：R1 = iPr，R2 = H；C2：R1 = Et，R2 = H；C3：R1 = Me，R2 = H；C4：R1 = Me，R2 = Me；C5：R1 = H，R2 = H；C6：R1 = F，R2 = H），通过红外光谱、元素分析、质谱和磁矩等方法进行合成与表征。对络合物C2和C3的X射线晶体学分析揭示了铬原子周围的八面体几何结构发生扭曲。在单加氧酶（MAO）的活化下，这些络合物表现出对乙烯齐聚（高达1.28 × 10^7 g·mol–1(Cr)·h–1）和乙烯聚合（高达6.30 × 10^6 g·mol–1(Cr)·h–1）的高度活性。齐聚物以对α-烯烃的高选择性（>99%）生成，其分布与Schultz–Flory规则极为相似。详细研究了各种反应参数，结果显示配体的立体效应和电子效应不仅影响了这些铬络合物的催化活性，还影响了所形成产物的分布。