Alkyl-substituted indenyl titanium precursors for syndiospecific ziegler-natta polymerization of styrene

Article abstract of DOI:10.1016/S0022-328X(96)06153-0

A variety of 1- and 3-substituted alkylindenes (R = H, Me, Et, tert-butyl, Me₃Si) as well as 2-methylindene and 3-(methylthio)indene have been prepared in good yields. The substituted indenes were converted into trimethylsilyl derivatives via reactions of intermediate organolithium complexes with chlorotrimethylsilane. The corresponding titanium complexes, (R-Ind)TiCl₃, were synthesized in excellent yield from reactions of the trimethylsilyl derivatives with TiCl₄. The titanium complexes were evaluated as styrene polymerization catalysts in toluene solution when activated by methylaluminoxane. Activities increased in the order: Cp < H₄ Ind < Ind < 1-(Me)Ind <2-(Me)Ind. A steep drop in activity was observed when R = Et, tert-butyl, and Me₃Si, corresponding to an increase in the steric bulk of the substituent in the catalyst precursor. 1-(MeS)IndTiCl₃ was found to be ineffective as a styrene polymerization catalyst. Syndiospecificities of the titanium complexes were generally very good (65-98%).