2-(1-(Arylimino)ethyl)-8-arylimino-5,6,7-trihydroquinolylcobalt dichloride: Synthesis and polyethylene wax formation

A series of 2-(1-(arylimino)ethyl)-8-arylimino-5,6,7-trihydroquinolylcobalt dichloride (aryl = 2,6-R1-4-R2C6H2) pre-catalysts were synthesized and structurally characterized by FT-IR and elemental analyses. The molecular structures of Co1 (R1 = Me, R2 = H), Co2 (R1 = Et, R2 = H) and Co5 (R1 = Et, R2 = Me) were determined by single-crystal X-ray diffraction analysis, and confirmed Co1 as a distorted trigonal bipyramidal geometry at the metal, whilst in Co2 and Co5 the metal is square-pyramidal. Upon treatment with either MAO or MMAO, all cobalt pre-catalysts exhibited highest activities at 60 °C for ethylene polymerization. The resultant polyethylenes, under optimization reaction parameters, possessed low molecular weight (waxes) and narrow polydispersity.

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► New tridentate cobalt dichloride pre-catalysts exhibits high activity to polymerize ethylene.
► Highly thermal-stable cobalt(II) pre-catalysts in ethylene polymerization.
► Single-site active species of cobalt pre-catalysts.
► Cobalt pre-catalysts showed higher activities than their iron analogs did.
► Polyethylene waxes with narrow polydispersity.