Dinitrogen Cleavage and Hydrogenation by a Trinuclear Titanium Polyhydride Complex

Both the Haber-Bosch and biological ammonia syntheses are thought to rely on the cooperation of multiple metals in breaking the strong N=N triple bond and forming an N-H bond. This has spurred investigations of the reactivity of molecular multimetallic hydrides with dinitrogen. We report here the reaction of a trinuclear titanium polyhydride complex with dinitrogen, which induces dinitrogen cleavage and partial hydrogenation at ambient temperature and pressure. By H-1 and N-15 nuclear magnetic resonance, x-ray crystallographic, and computational studies of some key reaction steps and products, we have determined that the dinitrogen (N-2) reduction proceeds sequentially through scission of a N-2 molecule bonded to three Ti atoms in a mu-eta(1):eta(2):eta(2)-end-on-side-on fashion to give a mu(2)-N/mu(3\)-N dinitrido species, followed by intramolecular hydrogen migration from Ti to the mu(2)-N nitrido unit.