The treatment of [{Ti(η(5)-C5Me5)}4(μ3-N)4] with NH3BH3 leads to the paramagnetic imidonitrido complex [{Ti(η(5)-C5Me5)}4(μ3-N)3(μ3-NH)], which can also be obtained by stepwise proton and electron transfer with HOTf and [K(C5Me5)].

Treatment of [Cl3Y{(μ3-NH)3Ti3(η(5)-C5Me5)3(μ3-N)}] with [K(C5Me5)] in toluene gives C10Me10 and the paramagnetic [K(μ-Cl)3Y{(μ3-NH)3Ti3(η(5)-C5Me5)3(μ3-N)}] (3) derivative. Crystallization of 3 in pyridine affords the potassium-free [Cl2(py)2Y{(μ3-NH)3Ti3(η(5)-C5Me5)3(μ3-N)}] (4) complex. Whereas the reaction of 3 with 1 equiv of 18-crown-6 leads to the molecular complex [(18-crown-6)K(μ-Cl)3Y{(μ3-NH)3Ti3(η(5)-C5Me5)3(μ3-N)}] (5), the analogous treatment of 3 with cryptand-222 affords the ion pair [K(crypt-222)][Cl3Y{(μ3-NH)3Ti3(η(5)-C5Me5)3(μ3-N)}] (6). The X-ray crystal structures of 4, 5, and 6 have been determined. Density functional theory (DFT) calculations have elucidated the electronic structure of these species, which should be regarded as containing trivalent Y bonded to the {(μ3-NH)3Ti3(η(5)-C5Me5)3(μ3-N)} metalloligand radical anion.

Alkylation of [{Ti(η(5)-C(5)Me(5))(μ-NH)}(3)(μ(3)-N)] with MeOTf occurs at the imido ligands to produce the methylamido derivative [Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)(μ-NH)(2)(μ-NHMe)(OTf)] which readily rearranges to form the methylimido complex [Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)(μ-NH)(μ-NH(2))(μ-NMe)(OTf)].

A series of titanium-group 3/lanthanide metal complexes have been prepared by reaction of [{Ti(η(5)-C(5)Me(5))(μ-NH)}(3)(μ(3)-N)] (1) with halide, triflate, or amido derivatives of the rare-earth metals. Treatment of 1 with metal halide complexes [MCl(3)(thf)(n)] or metal trifluoromethanesulfonate derivatives [M(O(3)SCF(3))(3)] at room temperature affords the cube-type adducts [X(3)M{(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}] (X = Cl, M = Sc (2), Y (3), La (4), Sm (5), Er (6), Lu (7); X = OTf, M = Y (8), Sm (9), Er (10)). Treatment of yttrium (3) and lanthanum (4) halide complexes with 3 equiv of lithium 2,6-dimethylphenoxido [LiOAr] produces the aryloxido complexes [(ArO)(3)M{(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}] (M = Y (11), La (12)). Complex 1 reacts with 0.5 equiv of rare-earth bis(trimethylsilyl)amido derivatives [M{N(SiMe(3))(2)}(3)] in toluene at 85-180 °C to afford the corner-shared double-cube nitrido compounds [M(μ(3)-N)(3)(μ(3)-NH)(3){Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}(2)] (M = Sc (13), Y (14), La (15), Sm (16), Eu (17), Er (18), Lu (19)) via NH(SiMe(3))(2) elimination. A single-cube intermediate [{(Me(3)Si)(2)N}Sc{(μ(3)-N)(2)(μ(3)-NH)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}] (20) was obtained by the treatment of 1 with 1 equiv of the scandium bis(trimethylsilyl)amido derivative [Sc{N(SiMe(3))(2)}(3)]. The X-ray crystal structures of 2, 7, 11, 14, 15, and 19 have been determined. The thermal decomposition in the solid state of double-cube nitrido complexes 14, 15, and 18 has been investigated by thermogravimetric analysis (TGA) and differential thermal analysis (DTA) measurements, as well as by pyrolysis experiments at 1100 °C under different atmospheres (Ar, H(2)/N(2), NH(3)) for the yttrium complex 14.

Treatment of [{Ti(η(5)-C5Me5)(μ-NH)}3(μ3-N)] (1) with zirconium or hafnium tetrachloride adducts [MCl4(thf)2] affords complexes [Cl3M{(μ3-N)(μ3-NH)2Ti3(η(5)-C5Me5)3(μ3-N)}] (M = Zr (2), Hf (3)). Titanium chloride complexes [Cl2Ti{(μ3-N)2(μ3-NH)Ti3(η(5)-C5Me5)3(μ3-N)}] (4) and [(Me2NH)ClTi{(μ3-N)3Ti3(η(5)-C5Me5)3(μ3-N)}] (5) are obtained by reaction of 1 with [TiCl4-x(NMe2)x] (x = 2, 3). The dimethylamine ligand in 5 is displaced by pyridine to give the analogue complex [(py)2ClTi{(μ3-N)3Ti3(η(5)-C5Me5)3(μ3-N)}] (6). Treatment of the titanium chloride complexes 4 and 5 with sodium cyclopentadienide or lithium bis(trimethylsilyl)amide reagents leads to the cube-type nitrido derivatives [RTi{(μ3-N)3Ti3(η(5)-C5Me5)3(μ3-N)}] (R = η(5)-C5H5 (7), N(SiMe3)2 (8)). The reaction of the zirconium trichloride complex 2 with [Tl(C5H5)] yields exclusively the dichloride-monocyclopentadienyl derivative [(η(5)-C5H5)Cl2Zr{(μ3-N)(μ3-NH)2Ti3(η(5)-C5Me5)3(μ3-N)}] (9). However, the treatment of 2 with excess [Na(C5H5)] causes further chloride replacement in 9 and subsequent cyclopentadiene elimination to give [(η(5)-C5H5)Zr{(μ3-N)3Ti3(η(5)-C5Me5)3(μ3-N)}] (10) via intermediates [(η(5)-C5H5)2ClZr{(μ3-N)Ti3(η(5)-C5Me5)3(μ-NH)2(μ3-N)}] (11) and [(η(5)-C5H5)ClZr{(μ3-N)2(μ3-NH)Ti3(η(5)-C5Me5)3(μ3-N)}] (12). Treatment of 2 or 9 with [Mg(C5H5)2] leads to the magnesium derivative [(η(5)-C5H5)Mg(μ-Cl)2(η(5)-C5H5)Zr{(μ4-N)(μ3-N)(μ3-NH)Ti3(η(5)-C5Me5)3(μ3-N)}] (13), which can be visualized as a result of the incorporation of one [Mg(η(5)-C5H5)Cl] moiety to complex 12. In contrast to the metathesis process with [M(C5H5)x] derivatives and subsequent C5H6 eliminations, the reaction of 2 with potassium pentamethylcyclopentadienide in toluene produces the paramagnetic derivative [K(μ-Cl)3Zr{(μ3-N)(μ3-NH)2Ti3(η(5)-C5Me5)3(μ3-N)}] (14) and C10Me10. Complex 14 reacts with one equivalent of 18-crown-6 or cryptand-222 to give the molecular complex [(18-crown-6)K(μ-Cl)3Zr{(μ3-N)(μ3-NH)2Ti3(η(5)-C5Me5)3(μ3-N)}] (15) or the ion pair [K(crypt-222)][Cl3Zr{(μ3-N)(μ3-NH)2Ti3(η(5)-C5Me5)3(μ3-N)}] (16). The X-ray crystal structures of 2, 8, 13 and 15 have been determined.