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.