Dinitrogen binding at a trititanium chloride complex and its conversion to ammonia under ambient conditions

Abstract

Reaction of [TiCp*Cl3] (Cp*=η5-C5Me5) 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 NH4Cl 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.