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

Reaction of [TiCpCl ] (Cp=η -C Me ) with one equivalent of magnesium in tetrahydrofuran at room temperature affords the paramagnetic trinuclear complex [{TiCp*(μ-Cl)} (μ -Cl)], which reacts with dinitrogen under ambient conditions to give the diamagnetic derivative [{TiCp*(μ-Cl)} (μ -η  : η  : η -N )] and the titanium(III) dimer [{TiCpCl(μ-Cl)} ]. 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 -η  : η  : η coordination mode of the dinitrogen molecule. The reaction of [{TiCp(μ-Cl)} (μ -η  : η  : η -N )] with excess HCl in tetrahydrofuran results in clean NH Cl formation with regeneration of the starting material [TiCpCl ]. Therefore, a cyclic ammonia synthesis under ambient conditions can be envisioned by alternating N /HCl atmospheres in a [TiCpCl ]/Mg(excess) reaction mixture in tetrahydrofuran.