From Five to Five: Titanium Ketimine Complexes with Monoaza-butadiene η4-Coordination Mode and Hidden η2-Imine Reactivity

Abstract

In the reactions of LTiCl3 (L: Cp*, Cp), Mg, and PhN═C(p-tolyl)2 (1) the formation of η4-ketimine complexes Cp*Ti(Cl)(η4-PhN═C(p-tolyl)2) (2a) and CpTi(Cl)(η4-PhN═C(p-tolyl)2) (2b) are observed. Their “nonclassic” five-membered titanium monoazabutadiene envelope coordination modes, involving one of the p-tolyl substituents, is confirmed by single crystal X-ray diffraction analysis of 2b. In reactions of 2 with aldehydes, ketones, alkynes, carbodiimides, isocyanates, isothiocyanates, and imines five-membered titanacycles are formed in a regioselective manner. This behavior is in agreement with a hidden η2-imine reactivity. All reaction products are fully characterized, including single crystal X-ray diffraction studies. For the PhC≡CH insertion products (4b, 4c) the formation of Ti–C(Ph) units are observed. By insertion of the isocyanate CyNCO the formation of a Ti–N bond in 6a is preferred in comparison to the insertion of the isothiocyanate PhNCS, where a Ti–S bond is formed (7a). By reacting 2a with ald...