Fluorosilyl-Substituted Cyclopentadienyltitanium(IV) Complexes: Synthesis, Structure, and Styrene Polymerization Behavior#

The synthesis and characterization of new halo-silyl-substituted titanium(IV) derivatives [TiCl3(η5-C5H4SiCl3)] (9), [TiCl3(η5-C5H4SiMe2F)] (10), [TiCl3(η5-C5H4SiMeF2)] (11), [TiCl3(η5-C5H4SiF3)] (12), and [TiF3(η5-C5H4SiMe2F)] (13) are reported. The reaction of lithiated trimethylsilylcyclopentadienide with Me2SiCl2, MeSiCl3, or SiCl4 gave chlorosilyl(trimethylsilyl)cyclopentadienes that were fluorinated with Me3SnF to yield fluorosilyl derivatives C5H4(SiMe2F)SiMe3 (4), C5H4(SiMeF2)SiMe3 (5), and C5H4(SiF3)SiMe3 (6), respectively. Addition of disilylated compounds 4−6 to a solution of TiCl4 gave the respective half-sandwich titanium complexes 10−12, which could be alternatively prepared by selective fluorination of the corresponding chlorosilyl-substituted cyclopentadienyltitanium(IV) trichlorides with Me3SnF. Completely fluorinated [TiF3(C5H4SiMe2F)] (13) was prepared from [TiCl3(C5H4SiMe2Cl)] (7) and 4 equiv of Me3SnF. The molecular structures of the pentameric 13 and the monomeric 10 were determined by X-ray diffraction analysis. The 47,49Ti NMR and UV−vis spectroscopy showed the electron-releasing nature of the SiMe2Cl, SiMe2F, SiMeCl2, and SiMeF2 substituents, whereas SiCl3 and SiF3 groups had electron-withdrawing properties. The catalytic behavior of these half-sandwich titanium compounds in styrene polymerization was studied in the presence of excess methylaluminoxane.