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)C 9 H 8 N]CrCl 3 (Ar = 2,6‐Me 2 Ph: Cr1 ; 2,6‐Et 2 Ph: Cr2 ; 2,6‐ i Pr 2 Ph: Cr3 ; 2,4,6‐Me 3 Ph: Cr4 ; 2,6‐Et 2 ‐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 × 10 6 g (PE) · mol –1 (Cr) · h –1 ]; even at 100 °C, the activity was still good [2.92 × 10 6 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.