Room temperature dinitrogen cleavage and hydrogenation with organometallic complexes of uranium

The conversion of dinitrogen into ammonia plays an important role in sustaining life on Earth and serves as a significant building block for our planet's future. The Haber-Bosch process, although a well-established method for converting hydrogen and nitrogen gases into ammonia using metal-based heterogeneous catalysts, requires an extensive industrial infrastructure, limiting its accessibility and flexibility. Molecular systems, whether supported or unsupported, offer the advantage of allowing fine-tuning of the metal properties and the involved elementary steps, which ultimately leads to a better understanding of the transformations. In this context, we present findings on the reactivity of dinitrogen with an organometallic uranium complex featuring the bulky Cp^ttt ligand (Cp^ttt = 1,2,4-tris(tert-butyl)cyclopentadienyl). This complex demonstrates the ability to cleave and hydrogenate dinitrogen under mild conditions, at ambient temperature and atmospheric pressure. Most notably, the rich redox chemistry of uranium enables the direct reduction of N₂ into a unique formal U^IV dimer featuring an end-on coordinated (N₂)^4- bridging ligand, the cornerstone of the observed reactivity.