Phosphinimide complexes with pendant hemilabile donors: synthesis, structure and ethylenepolymerization activity

Abstract

The phosphines tBu₂P(CH₂)₃ECH₂Ph (E = O (1), S (2)) converted to the corresponding phosphinimines (Me₃SiN)PtBu₂(CH₂)₃ECH₂Ph, E = O (3), S (4)) which were used to prepared the titanium complexes Cp′TiCl₂NPtBu₂(CH₂)₃ECH₂Ph, (E = O, Cp′ = Cp (5), Cp* (6); E = S, Cp′ = Cp (7), Cp* (8)). These species were subsequently methylated to the corresponding dimethyl-derivatives (9)–(12). Activation of (9)–(12) with both B(C₆F₅)₃ and [Ph₃C][B(C₆F₅)₄] was studied. For example, the [CpTiMe(NPtBu₂(CH₂)₃OCH₂Ph)][MeB(C₆F₅)₃] (13) reacted with THF to give [CpTiMe(THF)(NPtBu₂(CH₂)₃OCH₂Ph)][MeB(C₆F₅)₃] (14). Similar reactions gave the stable ion pairs [Cp′TiMe(NPtBu₂(CH₂)₃XCH₂Ph)][MeB(C₆F₅)₃] (X = O, Cp′ = Cp*, (15); X = S Cp′ = Cp, (16), Cp*(17)) and [Cp′TiMe(NPtBu₂(CH₂)₃XCH₂Ph)][B(C₆F₅)₄] (X = O, Cp′ = Cp, (18); Cp*(19); X = S, Cp′ = Cp, (20), Cp* (21)). The dihalide complexes (5)–(8), activated with MAO, proved to be ethylene polymerization catalysts of moderate activities. The dialkyl titanium complexes (9)–(12) activated with B(C₆F₅)₃ or [Ph₃C][B(C₆F₅)₄], gave catalysts that exhibited substantially higher activity and high molecular weight polyethylene. Polymerization at 60 °C rather than 30 °C significantly increased activity as well. The impact of the hemilabile donor with respect to catalyst activity is discussed. Crystallographic studies of (5) and (6) are reported.