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

Reaction of [TiCp*Cl₃ ] (Cp*=η⁵ -C₅ Me₅ ) with one equivalent of magnesium in tetrahydrofuran at room temperature affords the paramagnetic trinuclear complex [{TiCp*(μ-Cl)}₃ (μ₃ -Cl)], which reacts with dinitrogen under ambient conditions to give the diamagnetic derivative [{TiCp*(μ-Cl)}₃ (μ₃ -η¹  : η²  : η² -N₂ )] 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 μ₃ -η¹  : η²  : η² coordination mode of the dinitrogen molecule. The reaction of [{TiCp*(μ-Cl)}₃ (μ₃ -η¹  : η²  : η² -N₂ )] with excess HCl in tetrahydrofuran results in clean NH₄ Cl formation with regeneration of the starting material [TiCp*Cl₃ ]. Therefore, a cyclic ammonia synthesis under ambient conditions can be envisioned by alternating N₂ /HCl atmospheres in a [TiCp*Cl₃ ]/Mg(excess) reaction mixture in tetrahydrofuran.