The NN bond of molecular dinitrogen bridging two molybdenum atoms in the pentamethylcyclopentadienyl molybdenum complexes that bear ferrocenyldiphosphine as an auxiliary ligand is homolytically cleaved under visible light irradiation at room temperature to afford two molar molybdenum nitride complexes. Conversely, the bridging molecular dinitrogen is reformed by the oxidation of the molybdenum nitride complex at room temperature. This result provides a successful example of the cleavage and formation of molecular dinitrogen induced by a pair of two different external stimuli using a single system assisted by molybdenum complexes bearing ferrocenyldiphosphine under ambient conditions.Nitrogen fixation, the production of ammonia from molecular dinitrogen, is one of the most important chemical processes on earth because ammonia is widely used as an essential source of nitrogen fertilizers. Industrially, ammonia is produced from molecular dinitrogen and molecular dihydrogen using iron-based heterogeneous catalysts under harsh reaction conditions, such as quite high temperatures and pressures. [1] In the Haber-Bosch process, the rate-determining step is the dissociative chemisorption of dinitrogen on the surface of the iron catalyst, which includes adsorption of dinitrogen, cleavage of the NN triple bond, and the bonding of two nitrogen atoms to the iron surface as nitride species. [1] Although all these elementary steps are known to occur reversibly, it is still quite difficult to understand the heterogeneous reaction in detail on the atomic and molecular levels.Since the first discovery of a transition-metal-dinitrogen complex, [2] various stoichiometric and catalytic transformations using transition-metal-dinitrogen complexes have been well investigated toward the development of the next generation nitrogen fixation system. [3,4] During our study on the development of novel nitrogen fixation system under mild reaction conditions, [4b, 5] we have focused on use of ferrocenyldiphosphine as an auxiliary ligand chelating to molybdenum atom to capture and activate molecular dinitrogen. [6] We have now found that molecular dinitrogen is cleaved and reformed on the pentamethylcyclopentadienyl molybdenum complexes in medium oxidation states bearing ferrocenyldiphosphine as an auxiliary ligand. In this reaction system, molecular dinitrogen bridging two molybdenum moieties is cleaved under visible light irradiation at room temperature to afford the corresponding molybdenum nitride complex. Conversely, the bridging molecular dinitrogen is reformed by oxidation of the molybdenum nitride complex at room temperature. This result provides a successful example of the cleavage and formation of molecular dinitrogen induced by a pair of two different external stimuli (both photochemically and oxidatively) using a single system under ambient conditions.When the monocationic dinitrogen-bridged dimolybdenum complex chelated by 1,1'-bis(diethylphosphino)ferrocene (depf) [6a] (1), which was prepared by the reaction of molybdenum(II)-di...
