Bridging Titanium Nitrido Complexes Containing A Linear Ti-N-Ti Core with A Two-Coordinate Nitrido Ligand

A series of titanium μ₂-nitrido complexes supported by the triamidoamine ligand Xy-N₃N (Xy-N₃N={(3,5-Me₂C₆H₃)NCH₂CH₂}₃N^3-) is reported. The titanium azido complex [(Xy-N₃N)TiN₃] (1-N₃), prepared by salt metathesis of the chloride complex [(Xy-N₃N)TiCl] (1-Cl) with NaN₃, reacted with lithium metal or with alkali metal naphthalenides (alkali metal M=Na, K, and Rb) in THF to give the corresponding dinuclear μ₂-nitrido complexes M[(Xy-N₃N)Ti=N-Ti(Xy-N₃N)] (2-M; M=Li, Na, K, Rb). Single crystal X-ray diffraction studies of 2-Li, 2-Na, and 2-K revealed alkali metal dependent structures in the solid state. While 2-Li and 2-K contain a μ₂-nitrido ligand with a linear Ti-N-Ti core, 2-Na includes a μ₃-nitrido ligand as part of a T-shape Ti₂NaN fragment with the sodium cation weekly coordinated to the nitrido nitrogen atom. When the synthesis of the nitrido complexes was carried out in the presence of excess alkali metals, decomposition of the nitrido complexes was observed affording some intractable titanium species along with the trialkali metal salts [M₃(Xy-N₃N)] (3-M) (M=Li, Na, K, and Rb). These salts were also prepared by deprotonation of (Xy-N₃N)H₃ with the corresponding alkali metal hexamethyldisilazide and characterized by multinuclear NMR spectroscopy as well as single crystal X-ray diffraction.