Titanium isopropoxide complexes of a series of sterically demanding aryloxo based [N2O2]2− ligands as precatalysts for ethylenepolymerization

Abstract

Several titanium isopropoxide complexes [N,N′-bis(2-oxo-3-R₁-5-R₂-phenylmethyl)-N,N′-bis(methylene-p-R₃-C₆H₄)-ethylenediamine]Ti(OⁱPr)₂ [R₁ = t-Bu, R₂ = Me, R₃ = H (1b); R₁ = R₂ = t-Bu, R₃ = H, (2b); R₁ = R₂ = Cl, R₃ = H, (3b), R₁ = t-Bu, R₂ = Me, R₃ = Cl (4b); R₁ = R₂ = t-Bu, R₃ = Cl, (5b); R₁ = R₂ = R₃ = Cl, (6b)] supported over sterically demanding aryloxy based [N₂O₂]H₂ ligands have been designed as precatalysts for the ethylene polymerization. Specifically, the 1b–6b complexes, when treated with methylaluminoxane (MAO) under 88 ± 0.5 psi of ethylene at 30 °C for 3 h, produced polyethylene polymers of high molecular weight (M_w = ca. 7.2–8.3 × 10⁵ g mol⁻¹) having broad molecular weight distribution (PDI = ca. 13.1–14.6). The 1b–6b complexes were conveniently synthesized from the direct reaction of the [N₂O₂]H₂ ligands, 1a–6a, with Ti(OⁱPr)₄ in 69–86% yield.