Bimetallic Cooperative Cleavage of Dinitrogen to Nitride and Tandem Frustrated Lewis Pair Hydrogenation to Ammonia

Although reductive cleavage of dinitrogen (N-2) to nitride (N3-) and hydrogenation with dihydrogen (H-2) to yield ammonia (NH3) is accomplished in heterogeneous Haber-Bosch industrial processes on a vast scale, sequentially coupling these elementary reactions together with a single metal complex remains a major challenge for homogeneous molecular complexes. Herein, we report that the reaction of a chloro titanium triamidoamine complex with magnesium effects complete reductive cleavage of N-2 to give a dinitride dititanium dimagnesium ditriamidoamine complex. Tandem H-2 splitting by a phosphine-borane frustrated Lewis pair (FLP) shuttles Hatoms to the N3-, evolving NH3. Isotope labelling experiments confirmed N-2 and H-2 fixation. Though not yet catalytic, these results give unprecedented insight into coupling N-2 and H-2 cleavage and N-H bond formation steps together, highlight the importance of heterobimetallic cooperativity in N-2 activation, and establish FLPs in NH3 synthesis.