Metallo-Wittig chemistry of an alkylidene to form a terminal titanium oxo complex
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)TiCHtBu(OTf) (1) and two equivalents of benzophenone, by extruding the olefin Ph2CCHtBu. 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.
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