Dinitrogen cleavage and hydrogenation to ammonia with a uranium complex

The Haber-Bosch process produces ammonia(NH3) from dinitrogen(N2) and dihydrogen(H2),but re quires high temperature and pressure.Before iron-based catalysts were exploited in the current industrial Haber-Bosch process,uranium-based materials served as effective catalysts for production of NH3from N2.Although some molecular uranium complexes are known to be capable of combining with N2,further hydrogenation with H2forming NH3has not been reported to date.Here,we describe the first example of N2cleavage and hydrogenation with H2to NH3with a molecular uranium complex.The N2cleavage product contains three uranium centers that are bridged by three imido μ2-NH ligands and one nitridoμ3-N ligand.Labeling experiments with15N demonstrate that the nitrido ligand in the product originates from N2.Reaction of the N2-cleaved complex with H2or H+forms NH3under mild conditions.A synthetic cycle has been established by the reaction of the N2-cleaved complex with trimethylsilyl chloride.The isolation of this trinuclear imido-nitrido product implies that a multi-metallic uranium assembly plays an important role in the activation of N2.