With the two components of H2 splitting and N2 reduction to a (N2) 2-in hand, we focused on their synergy in relation to N2 hydrogenation, relevant to the Haber-Bosch process. We were interested in the reactivity of 5 towards H2 as Ln III dinitrogen complexes, which feature formally oxidized metal centers, have been shown to act as "masked" low-valent synthons. In these examples, twoelectron reduction processes occurred upon addition of reducible substrates (CO, CO2, aromatic Nheterocycles), with the systematic release of the N2 ligand. Similar reductive reactivity has also been recently reported in the case of N2 complexes of U IV , Mg II and Ca II , where the coordinated and reduced (N2) 2-moiety acted as a redox-active ligand, able to reversibly store two electrons. Initial reactivity attempts in NMR tubes showed that heating a purple suspension of 5 in C6D6 under H2 atmosphere at 80 °C led to the full consumption of 5 over several hours, as evidenced by the formation of a clear colorless solution. H NMR analysis revealed the formation of 3-H as a major product (ca. 90%) along with a minor species (ca. 10%) assigned to [Lu(Cp ttt )2NH2] (6) (Figure ). The identity of 6 was testified by N labelling experiments as well as independent in situ synthesis of 6 upon exposure of 2 with NH3 gas (Figures ). In the 1 H NMR spectrum, the singlet at  3.07 ppm for the NH2 protons in 6 was replaced by a doublet ( 1 JHN = 62.8 Hz) when performing the experiment with the isotopically labelled 5-15 N. Accordingly, the 15 N NMR spectrum of 6-15 N showed a triplet at  110.1 ppm with the same coupling constant (Figure ). In addition, protonolysis experiments with anhydrous HCl confirmed the formation of NH4Cl and 15 NH4Cl, as evidenced by the presence in the 1 H NMR spectra of the characteristic triplet and doublet signals, respectively, in the range  7.2-7.7 ppm (see Figure ). The origin of the NH2 hydrogen atoms in 6 and 6-15 N was confirmed by reaction of 5 and 5-15 N with D2, leading to the disappearance of the NH2 resonance at  3.07 ppm while the signals for the Cp ttt ligand remained unchanged (Figures S22-23).