Synthesis, characterization and catalytic behavior toward ethylene of 2-[1-(4,6-dimethyl-2-benzhydrylphenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridylmetal (iron or cobalt) chlorides

Abstract

A series of 2-[1-(4,6-dimethyl-2-benzhydrylphenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridines was synthesized and used to prepare the iron(II) and cobalt(II) chloride complexes thereof. All organic compounds were fully characterized by elemental analysis, IR and NMR (¹H/¹³C) spectroscopy, whilst the metal complexes were characterized by elemental analysis and IR spectroscopy as well as by single-crystal X-ray diffraction studies (for two representative cobalt complexes), which revealed that the geometry at the metal was either pseudo-square-pyramidal or trigonal bipyramidal. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all metal complex pre-catalysts exhibited high activities for ethylene polymerization. The iron pre-catalysts show much higher activity than did their cobalt analogues; however, the iron catalytic systems generally produced polyethylene of wide molecular weight polydispersity. At elevated reaction temperature, the polyethylene was of lower molecular weight, but revealed narrow polydispersity.