Molecular Nitrides with Titanium and Rare-Earth Metals

A series of titanium-group 3/lanthanide metal complexes have been prepared by reaction of [{Ti(η5-C5Me5)(μ-NH)}3(μ3-N)] (1) with halide, triflate, or amido derivatives of the rare-earth metals. Treatment of 1 with metal halide complexes [MCl3(thf)n] or metal trifluoromethanesulfonate derivatives [M(O3SCF3)3] at room temperature affords the cube-type adducts [X3M{(μ3-NH)3Ti3(η5-C5Me5)3(μ3-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)3M{(μ3-NH)3Ti3(η5-C5Me5)3(μ3-N)}] (M = Y (11), La (12)). Complex 1 reacts with 0.5 equiv of rare-earth bis(trimethylsilyl)amido derivatives [M{N(SiMe3)2}3] in toluene at 85–180 °C to afford the corner-shared double-cube nitrido compounds [M(μ3-N)3(μ3-NH)3{Ti3(η5-C5Me5)3(μ3-N)}2] (M = Sc (13), Y (14), La (15), Sm (16), Eu (17), Er (18), Lu (19)) via NH(SiMe3)2 elimination. A single-cube intermediate [{(Me3Si)2N}Sc{(μ3-N)2(μ3-NH)Ti3(η5-C5Me5)3(μ3-N)}] (20) was obtained by the treatment of 1 with 1 equiv of the scandium bis(trimethylsilyl)amido derivative [Sc{N(SiMe3)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, H2/N2, NH3) for the yttrium complex 14.