Synthesis and Characterization of the Titanium Bisamide Ti{N(H)AriPr6}2 (AriPr6 = C6H3‑2,6-(C6H2‑2,4,6‑iPr3)2 and Its TiCl{N(H)AriPr6}2 Precursor: Ti(II) → Ti(IV) Cyclization

The titanium bisamido complex Ti­{N­(H)­AriPr6}2 (AriPr6 = C6H3-2,6-(C6H2-2,4,6-iPr3)2 (2), along with its three-coordinate titanium­(III) precursor, TiCl­{N­(H)­AriPr6}2 (1), have been synthesized and characterized. Compound 1 was obtained via the stoichiometric reaction of LiN­(H)­AriPr6 with the Ti­(III) complex TiCl3·2NMe3 in trimethylamine. Reduction of 1 with 1 equiv of KC8 afforded Ti­{N­(H)­AriPr6}2 (2) in moderate yield. Both 1 and 2 were characterized by X-ray crystallography, NMR, and IR spectroscopy, magnetic studies, and by density functional theory (DFT) computations. The precursor 1 has quasi-four-coordinate coordination at the titanium atom, with bonding to two amido nitrogens and a chlorine as well as a secondary interaction to a flanking aryl ring of a terphenyl substituent. Compound 2 displays a very distorted four-coordinate metal environment in which the titanium atom is bound to two amido nitrogens and to two carbons from a terphenyl aryl ring. This structure is in sharp contrast to the expected two-coordinate linear structure that was observed in its first row metal (V–Ni) analogues. Magnetic studies confirm a d1 electron configuration for 1 but indicate that Ti­{N­(H)­AriPr6}2 (2) is diamagnetic at ambient temperature consistent with the oxidation of titanium to Ti­(IV). The different structure of 2 is attributed to the high reducing tendency of the Ti­(II) in comparison to the other metals.