Metallo-Wittig chemistry of an alkylidene to form a terminal titanium oxo complex

Abstract

We report the synthesis and structure of a titanium(IV) benzophenone adduct bearing a terminal oxo ligand, (PNP)Ti = O(OTf)(OCPh₂) (PNP⁻ = N[2-PⁱPr₂-4-methylphenyl]₂) (2). Complex 2 is readily synthesized in 71% yield from the previously reported titanium alkylidene (PNP)TiCH^tBu(OTf) (1) and two equivalents of benzophenone, by extruding the olefin Ph₂CCH^tBu. Treatment of benzophenone adduct 2 with a bulky aryloxide salt results in formation of (PNP)TiO(OAr) (3) (OAr⁻ = 2,6-bis(diphenylmethyl)-4-tert-butylphenoxide), concurrent with salt elimination and displacement of the benzophenone. Complexes 2 and 3 were characterized by single-crystal X-ray diffraction and a variety of spectroscopic techniques, including NMR, UV-Vis-NIR spectroscopies, and TD-DFT calculations.