Vinyl‐Polyethylene Waxes with Narrow Dispersity Obtained by Using a Thermally Robust [Bis(imino)trihydroquinolyl]chromium Catalyst

Five structurally related chromium(III) complexes, [2-(ArNCMe)-8-(NAr)C9H8N]CrCl3 (Ar = 2,6-Me2Ph Cr1, 2,6-Et2Ph Cr2, 2,6-i-Pr2Ph Cr3, 2,4,6-Me3Ph Cr4, 2,6-Et2-4-MePh Cr5), each bearing an unsymmetrical bis(imino)trihydroquinoline ligand, have been synthesized in good yield and fully characterized. The molecular structure of Cr2 reveals a distorted octahedral geometry at the metal center with the sterically bulky N,N,N-ligand adopting a mer-configuration. On activation with MAO or MMAO, Cr1 - Cr5, were highly active catalysts for ethylene polymerization operating most effectively at 80 ◦C (up to 15.96 × 106 g (PE)*mol-1 (Cr)*h-1); even at 100 ◦C the activity still maintained a good level (2.92 × 106 g (PE)*mol-1 (Cr)*h-1). Highly linear polyethylene waxes of low molecular weight and narrow distribution (1.1 - 1.8), incorporating predominantly vinyl/methyl and some methyl/methyl end-groups, are a feature of the materials obtained. The influence of steric/electronic changes to the pre-catalyst and polymerization reaction parameters on both the catalytic activities as well as the properties of the polymeric product has been the subject of a detailed investigation.

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