Reactivity of boranes with a titanium(IV) amine tris(phenolate) alkoxide complex; formation of a Ti(IV) tetrahydroborate complex, a Ti(III) dimer and a Ti(IV) hydroxide Lewis acid adduct

Treatment of the titanium(IV) alkoxide complex [Ti((OPr)-Pr-i)(OC6Me2H2CH2)(3)N] (2) with BH3 center dot THF, as part of a study into the utility and reactivity of (2) in the metal mediated borane reduction of acetophenone, results in alkoxide-hydride exchange and formation of the structurally characterised titanium(IV) tetrahydroborate complex [Ti{BH4}(OC6Me2H2CH2)(3)N] (3). Complex (3) readily undergoes reduction to form the isolable titanium(III) species [Ti(OC6Me2H2CH2)(3)N](2) (4). Reaction of (2) with B(C6F5)(3) results in formation of the Lewis acid adduct [Ti(OC6Me2H2CH2)(3)N][HO center dot B(C6F5)(3)] (5). In comparison, treatment of the less sterically encumbered alkoxide Ti((OPr)-Pr-i)(4) with B(C6F5)(3) results in alkoxide-aryl exchange and formation of the organometallic titanium complex [Ti((OPr)-Pr-i)(3)(C6F5)](2) (6). The molecular structures of 3, 4, 5 and 6 have been determined by X-ray diffraction.