Dinitrogen Binding at a Trititanium Chloride Complex and Its Conversion to Ammonia under Ambient Conditions

Abstract

Reaction of [TiCp*Cl 3 ] (Cp* = η 5 -C 5 Me 5 ) with one equivalent of magnesium in tetrahydrofuran at room temperature affords the paramagnetic trinuclear complex [{TiCp*(μ-Cl)} 3 (μ 3 -Cl)], which reacts with dinitrogen under ambient conditions to give the diamagnetic derivative [{TiCp*(μ-Cl)} 3 (μ 3 -η 1 : η 2 : η 2 -N 2 )] and the titanium(III) dimer [{TiCp*Cl(μ-Cl)} 2 ]. The structure of the trinuclear mixed-valence complexes has been studied by experimental and theoretical methods and the latter compound represents the first well-defined example of the μ 3 -η 1 : η 2 : η 2 coordination mode of the dinitrogen molecule. The reaction of [{TiCp*(μ-Cl)} 3 (μ 3η 1 : η 2 : η 2 -N 2 )] with excess HCl in tetrahydrofuran results in clean NH 4 Cl formation with regeneration of the starting material [TiCp*Cl 3 ]. Therefore, a cyclic ammonia synthesis under ambient conditions can be envisioned by alternating N 2 /HCl atmospheres in a [TiCp*Cl 3 ]/Mg(excess) reaction mixture in tetrahydrofuran.

Monocyclopentadienyltitanium(III) Complexes with Hydridoborato Ligands

“…Reduction of the latter titanium(IV) trichloride precursor with an excess of magnesium led to a mixed-valence Ti II /Ti III trinuclear complex [{Ti(η 5 -C 5 Me 5 )(μ-Cl)} 3 (μ 3 -Cl)] capable of activating dinitrogen under ambient conditions. 27 Analogous treatment of [Ti(η 5 -C 5 Me 5 )X 3 ] with excess LiAlH 4 in ethereal solvents (L) produced titanium(II) species [{Ti(η 5 -C 5 Me 5 )(μ-H)} 2 {(μ-H) 2 AlXL} 2 ] (L = thf, X = Cl, Br; L = OEt 2 , X = Cl), while the reactions with the milder reductant LiBH 4 gave titanium-(III) tetrahydridoborato complexes. 28 In particular, the X-ray crystal structure of the bis(tetrahydridoborato) derivative showed a dimer [{Ti(η 5 -C 5 Me 5 )(BH 4 )(μ-BH 4 )} 2 ] with two bridging BH 4 ligands between the metal centers (Scheme 1).…”

Binding of Nitriles and Isonitriles to V(III) and Mo(III) Complexes: Ligand vs Metal Controlled Mechanism

“…The steric factors of the R group may also provide information in that regard. In addition, since the N≡N molecule has at its disposal the formation of a range of bridged structures between two or more metals, 3 the terminal R group in RCN normally limits binding to one metal center in typically an end-on η 1 or side-on η 2 architecture. 4 …”