Homogeneous pathways for converting N2 to NH3 have been made recently, principally with transition metals and uranium. From a mechanistic point of view, the conversion of N2 and H2 to ammonia involves different possible scenarios. In the first one, H2 cleavage occurs first, forming hydride species, which then transfer the hydrogen atoms to dinitrogen. In the second one, N2 cleavage occurs first, and the resulting nitride is hydrogenated. In the last scenario, synergetic hydrogenation of a reduced N2 ligand occurs. Among these possibilities, the role of multi-metallic hydride species in the hydrogen atom transfer to dinitrogen has been documented by Hou and co-workers. Hydrogenation of bridged nitrido units, formed after cleavage of dinitrogen, has been recently reported by the groups of It is noteworthy that the direct hydrogenation of reduced dinitrogen adducts has been only described with an organometallic Zr complex. In the case of rare-earth (RE) elements, which are constituted by the lanthanides along with the closely related Y and Sc, very rare examples of N2 functionalization have been disclosed.