Catalytic Dinitrogen Reduction to Ammonia at a Triamidoamine-Titanium Complex.

Catalytic reduction of N to NH by a Ti complex has been achieved, thus now adding an early d-block metal to the small group of mid- and late-d-block metals (Mo, Fe, Ru, Os, Co) that catalytically produce NH by N reduction and protonolysis under homogeneous, abiological conditions. Reduction of [Ti (Tren )X] (X=Cl, 1A; I, 1B; Tren =N(CH CH NSiMe ) ) with KC affords [Ti (Tren )] (2). Addition of N affords [{(Tren )Ti } (μ-η :η -N )] (3); further reduction with KC gives [{(Tren )Ti } (μ-η :η :η :η -N K )] (4). Addition of benzo-15-crown-5 ether (B15C5) to 4 affords [{(Tren )Ti } (μ-η :η -N )][K(B15C5) ] (5). Complexes 3-5 treated under N with KC and [R PH][I], (the weakest H source yet used in N reduction) produce up to 18 equiv of NH with only trace N H . When only acid is present, N H is the dominant product, suggesting successive protonation produces [{(Tren )Ti } (μ-η :η -N H )][I] , and that extruded N H reacts further with [R PH][I]/KC to form NH .