Chromium(III) complexes ligated by 2-(1-isopropyl-2-benzimidazolyl)-6-(1-(arylimino)ethyl)pyridines: Synthesis, characterization and their ethylene oligomerization and polymerization

A series of chromium(III) complexes bearing 2-(1-isopropyl-2-benzimidazolyl)-6-(1-(arylimino)ethyl)pyridines were synthesized and characterized by IR spectroscopic and elemental analysis. The X-ray crystallographic analysis revealed a distorted octahedral geometry of the chromium complexes. When activated by Et2AlCl, MAO or MMAO, these chromium complexes exhibited catalytic activities for ethylene oligomerization and polymerization; while the good to high activities (up to 3.95 × 106 g mol−1 (Cr) h−1) were observed in the catalytic systems with MMAO. Therefore, various reaction parameters of the catalytic system with MMAO were investigated in detail. The steric and electronic effects of ligands affected the catalytic activities and the distribution of the products predominantly. Interestingly, sometimes their distributions of oligomers did not resemble the rules of Schulz-Flory or Poisson due to the hexenes produced in low yield.