Reactions of Organotitanoxane Fluorides with AlR₃ (R = Me, Et, CH₂Ph) and Me₃SiCl: X-ray Crystal Structures of [C₅Me₅Ti(μ-O)]₄F[(μ-F)AlMe₃]₃, [C₅Me₅Ti(μ-O)]₄F₃[(μ-F)Al(CH₂Ph)₃], [C₅Me₅Ti(μ-O)Et]₄, and (C₅Me₅)₄Ti₄O₅X₂ (X = Cl and F)^†

A new pentamethylcyclopentadienyl titanoxane fluoride (C5Me5)4Ti4O5F2 (1b) has been synthesized from (C5Me5)4Ti4O5Cl2 using the fluorinating reagent Me3SnF. The fluorination of organotitanoxane chlorides proceeds via a proposed intermediate similar to the four-membered ring Ti(μ-Cl)(μ-F)Sn and the bridged Ti(μ-F)ClSnMe3 species. The reactions of 1b and [C5Me5Ti(μ-O)F]4 with AlR3 (R = Me, Et, CH2Ph) afforded the thermally unstable adducts [C5Me5Ti(μ-O)]4F4-n[(μ-F)AlR3]n (n = 1−4), which proceed with selective exchange of fluorine atoms for alkyl groups to give an eight-membered alkylated ring compound [C5Me5Ti(μ-O)R]4. The reactions of 1b and [C5Me5Ti(μ-O)F]4 with Me3SiCl result in exchange of fluorine for chlorine atoms. Moreover, using an excess of Me3SiCl leads to a novel oxygen−chlorine exchange reaction to give C5Me5TiCl3. The crystal structures of complexes (C5Me5)4Ti4O5X2 (X = Cl (1a), F (1b)), [C5Me5Ti(μ-O)]4F[(μ-F)AlMe3]3 (2b), [C5Me5Ti(μ-O)]4F3[(μ-F)Al(CH2Ph)3] (3a), and [C5Me5Ti(μ-O)Et]4 (4) have been determined by X-ray diffraction studies. Both chlorides and fluorides in 1a and 1b, respectively, are oriented to the exo position of their “butterfly” structures. The bond lengths of the terminal fluorines (Ti−Ft) in compounds 2b and 3a are discussed with respect to the deviation from the bond lengths of the bridging fluorines (Ti−Fb−Al). The structure of 4 displays a nonplanar Ti4O4 ring conformation as shown in 2b and 3a.