The exact mechanism of the N2 hydrogenation reactivity remains elusive to date but control experiments revealed no reaction between 3-H and N2 at different temperatures (Figure ), nor between 3-H and 5. Elucidation of the detailed mechanism by DFT studies is in progress and will be reported in due course. Although M-NH2 moieties have been obtained upon hydrogenation of terminal uranium or iridium nitride complexes, 59 the inaccessibility of oxidation states higher than +III for Lu would prevent the formation of a similar intermediate. As such, the formation of 6 is bound to proceed through direct hydrogenation of the N2-ligated complex 5, an unprecedented reactivity in RE chemistry.