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‐iPr2Ph: Cr3; 2,4,6‐Me3Ph: Cr4; 2,6‐Et2‐4‐MePh: Cr5), each bearing an unsymmetrical bis(imino)trihydroquinoline ligand, were 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 methylaluminoxane (MAO) or modified MAO, 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 was still good [2.92 × 106 g (PE)·mol–1 (Cr)·h–1]. Highly linear polyethylene waxes of low molecular weight and narrow molecular weight distribution (polydispersity index: 1.1–1.8), incorporating predominantly vinyl/methyl and some methyl/methyl end groups were obtained. The influence of steric/electronic changes to the precatalyst and polymerization reaction parameters on the catalytic activity and the properties of the polymer product were the subject of a detailed investigation.