Titanium and vanadium complexes with tetraphenylimidodiphosphinate

Treatment of [Ti(OPri)2Cl2] with K(tpip) (tpip− = [N(PPh2O)2]−) followed by chlorination with HCl afforded cis-[Ti(tpip)2Cl]2 (1). Reduction of 1 with Na/Hg in THF gave [Ti(tpip)3] (2), which could also be prepared from [TiCl3(THF)3] and K(tpip). Recrystallization of [V(O)(tpip)2] (3) from CH2Cl2–Et2O in air afforded trinuclear [{V(O)}3(μ-tpip)3(μ-O)3] (4). Treatment of [Cr(NBut)2Cl2] and [Cr(NBut)Cl3(dme)] (dme = 1,2-dimethoxyethane) with [Ag(tpip)]4 led to isolation of [Cr(tpip)3] (6) and [Cr(NBut)(tpip)2Cl] (7), respectively. The Ti- and V-tpip complexes are capable of catalyzing oxidation of sulfides with tert-butyl hydroperoxide and H2O2. The crystal structures of 1, 2, and 4 have been determined.