2-(1-{2,6-Bis[bis(4-fluorophenyl)methyl]-4-methylphenylimino}ethyl)-6-[1-(arylimino)ethyl]pyridylcobalt dichlorides: Synthesis, characterization and ethylene polymerization behavior

摘要

A series of 2-(1-{2,6-bis[bis(4-fluorophenyl)methyl]-4-methylphenyl-imino} ethyl)-6-[1-(arylimino)ethyl]pyridylcobalt(II) chloride complexes (Co1-Co5) was synthesized and characterized by FT-IR spectroscopy and elemental analysis. The molecular structures of the representative cobalt complexes Co1 (R~1 = Me, R~2 = H), Co4 (R~1 = Me, R~2 = Me) and Co5 (R~1 = Et, R~2 = Me) were determined by single crystal X-ray diffraction, and revealed a pseudo-square-pyramidal geometry at cobalt. Upon activation with either MMAO or MAO, all cobalt complex pre-catalysts exhibited high activities [up to the range of 10~7 g of PE (mol of Co) ~(-1) h~(-1)] toward ethylene polymerization. The influence of reaction parameters and the nature of the ligands were investigated in detail on the catalytic activities of the corresponding complexes and properties of the resultant polyethylene. The cobalt system revealed single-site behavior and produced polyethylene with narrow molecular distribution. Compared to the use of MAO, the use of MMAO produced polyethylene of higher molecular weight.