Synthesis and reactivity of trimethylsilyl substituted mono(cyclopentadienyl)titanium alkyl complexes

The preparation of a series of titanium half-sandwich compounds Ti(η⁵-C₅H_5−x (SiMe₃) _x R₃] (x = 1–3, R = Cl, Me) and their reactivity for propene polymerization is reported. The compounds 1–3 polymerize propene, albeit in a much lower activity than the reported Ti(η⁵-C₅Me₅Me₃]/B(C₆F₅)₃ catalyst. Unlike the reported Ti(η⁵-C₅Me₅Me₃]/B(C₆F₅)₃ catalyst, the quasi living polymerization was not observed. Instead, we observe rather unusual temperature effects when the trityl salt Ph₃C]B(C₆F₅)₄] was used as activator. The activity increases with increasing temperature, whereas when B(C₆F₅)₃ is used a decrease is observed The rather broad (>2) PDI indicates multisite catalysts, and ¹³C-NMR indicates predominantly atactic polypropene. The solid state structure of the hydrolysis product {Ti(η⁵-C₅H₄(SiMe₃)Cl₂}O] (4) was determined.