Ammonolysis of Mono(pentamethylcyclopentadienyl) Titanium(IV) Derivatives

Ammonolyses of mono(pentamethylcyclopentadienyl) titanium(IV) derivatives Ti(eta5-C5Me5)X3 (X = NMe2, Me, Cl) have been carried out in solution to give polynuclear nitrido complexes. Reaction of the tris(dimethylamido) derivative Ti(eta5-C5Me5)(NMe2)3 with excess of ammonia at 80-100 degrees C gives the cubane complex [Ti(eta5-C5Me5)4(mu3-N)4] (1). Treatment of the trimethyl derivative Ti(eta5-C5Me5)Me3 with NH3 at room temperature leads to the trinuclear imido-nitrido complex [Ti(eta/5-CsMes)(mu-NH)3(mu3-N)] (2) via the intermediate [Ti(eta5-C5Me5)Me2(mu-NH)2] (3). The analogous reaction of Ti(eta5-C5Me5)Me3 with 2,4,6-trimethylaniline (ArNH2) gives the dinuclear imido complex [Ti(eta5-C5Me5)Me)2(mu-NAr)2] (4) which reacts with ammonia to afford [Ti(eta5-C5Me5)(NH2)2(mu-NAr)2] (5). Complex 2 has been used, by treatments with the tris(dimethylamido) derivatives Ti(eta5-C5H5-nRn)(NMe2)3, as precursor of the cubane nitrido systems [Ti4(eta5-C5Me5)3(eta5-C5H5-nRn)(mu3-N)4] R = Me n = 5 (1), R = H n = 0 (6), R = SiMe3 n = 1 (7), R = Me n = 1 (8) via dimethylamine elimination. Reaction of Ti(eta5-C5Me5)Cl3 or Ti(eta5-C5Me5)(NMe2)Cl2 with excess of ammonia at room temperature gives the dinuclear complex [Ti2(eta5-C5Me5)2Cl3(NH3)(mu-N)] (9) where an intramolecular hydrogen bonding and a nonlineal nitrido ligand bridge the "Ti(eta5-C5Me5)Cl(NH3)" and "Ti(eta5-C5Me5)Cl2" moieties. The molecular structures of [Ti(eta5-C5Me5)Me2 (mu-NAr)2] (4) and [Ti2(eta5-C5Me5)2Cl3(NH3)(mu-N)] (9) have been determined by X-ray crystallographic studies. Density functional theory calculations also have been conducted on complex 9 to confirm the existence of an intramolecular N-H...Cl hydrogen bond and to evaluate different aspects of its molecular disposition.