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

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 3 -η 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.