Ni(2,2':6',2''-terpyridine): a high-spin octahedral formal Ni(0) complex.

We have synthesised and characterised the complex Ni(tpy) (tpy = 2,2':6',2''-terpyridine). This formally Ni(0) complex is paramagnetic both in the solid state and in solution ( = 2). The crystal structure shows an octahedral geometry, with molecules arranged in independent dimers involving π-stacking between pairs of complexes.

Low-Valent Titanium Species Stabilized with Aluminum/Boron Hydride Fragments.

Low-valent titanium species were prepared by reaction of [TiCp*X ] (Cp*=η -C Me ; X=Cl, Br, Me) with LiEH (E=Al, B) or BH (thf), and their structures elucidated by experimental and theoretical methods. The treatment of trihalides [TiCp*X ] with LiAlH in ethereal solvents (L) leads to the hydride-bridged heterometallic complexes [{TiCp*(μ-H)} {(μ-H) AlX(L)} ] (L=thf, X=Cl, Br; L=OEt , X=Cl). Density functional theory (DFT) calculations for those compounds reveal an open-shell singlet ground state with a Ti-Ti bond and can be described as titanium(II) species.

Preparation of Dimeric Monopentamethylcyclopentadienyltitanium(III) Dihalides and Related Derivatives.

The synthesis, crystal structure, and reactivity of a series of half-sandwich titanium(III) dihalide complexes [Ti(η-CMe)X] (X = Cl, Br, I) and several of its Lewis base derivatives were investigated. The reaction of the trihalides [Ti(η-CMe)X] (X = Cl (), Br (), I ()) with LiAlH (≥1 equiv) in toluene at room temperature results in the formation of the halide-bridged dimers [{Ti(η-CMe)X(μ-X)}] (X = Cl (), Br (), I ()). The treatment of with [Li{N(SiMe)}] (≥2 equiv) at room temperature affords the precipitation of the amido titanium(III) complex [{Ti(η-CMe)(μ-Cl){N(SiMe)}}] (), but analogous reactions of with other lithium reagents [LiR] (R = Me, CHSiMe, NMe) lead to disproportionation into titanium(IV) [Ti(η-CMe)R] and presumably titanium(II) derivatives.

Ammonia-Borane Derived BN Fragments Trapped on Bi- and Trimetallic Titanium(III) Systems.

Titanium(III) complexes containing unprecedented (NH BH NHBH ) and {N(BH ) } ligands have been isolated, and their structures elucidated by a combination of experimental and theoretical methods. The treatment of the trimethyl derivative [TiCp*Me ] (Cp*=η -C Me ) with NH BH (3 equiv) at room temperature gives the paramagnetic dinuclear complex [{TiCp*(NH BH )} (μ-NH BH NHBH )], which at 80 °C leads to the trinuclear hydride derivative [{TiCp*(μ-H)} {μ -N(BH ) }]. The bonding modes of the anionic BN fragments in those complexes, as well as the dimethylaminoborane group trapped on the analogous trinuclear [{TiCp*(μ-H)} (μ -H)(μ -NMe BH )], have been studied by X-ray crystallography and density functional theory (DFT) calculations.

Group 4 Half-Sandwich Tris(trimethylsilylmethyl) Complexes: Thermal Decomposition and Reactivity with N,N-Dimethylamine-Borane.

The thermal decomposition of group 4 trimethylsilylmethyl derivatives [M(η-CMe)(CHSiMe)] (M = Ti (1), Zr (2), Hf (3)) in solution and their reactivity with N,N-dimethylamine-borane were investigated. Heating of hydrocarbon solutions of compounds 2 and 3 at 130-200 °C results in the elimination of SiMe and the clean formation of the singular alkylidene-alkylidyne zirconium and hafnium compounds [{M(η-CMe)}{(μ-CH)SiMe}(μ-CSiMe)] (M = Zr (4), Hf (5)). The reaction of 2 and 3 with NHMeBH (≥1 equiv) at room temperature affords the dialkyl(dimethylamidoborane) complexes [M(η-CMe)(CHSiMe)(NMeBH)] (M = Zr (6), Hf (7)).