To the best of our knowledge, direct H2 splitting by molecular lanthanide complexes is unprecedented to date. This strategy offers a novel route for the synthesis of molecular Ln III -H species, typically obtained by hydrogenolysis of Ln-alkyl bonds. It can be noted that, in rare instances, molecular RE hydrides have been obtained upon treatment of trivalent complexes with strong alkali metal reductants. 45a,47 However, such reactions did not involve H2 activation but rather undefined hydrogen abstraction from solvents or possible aromatic C-H activation. 47e Although elemental zerovalent lanthanides are known to react with hydrogen at elevated temperatures to afford binary Ln hydrides, no such reaction has been observed with molecular Ln species. Weak coordination of H2 to a lanthanide complex has only been spectroscopically evidenced for the base-free Eu II complex [Eu(C5Me5)2], in which case no metal oxidation and formation of a hydride complex occurred. Very recently, this phenomenon has been extended to 5f elements with spectroscopic and computational evidence of the reversible formation of a U III -H2 complex. Regarding heterogeneous lanthanide systems, nondissociative dihydrogen binding has also been very recently evidenced by solid-state NMR studies under pressure of H2. Finally, it is worth noting that, within the actinide series, some U II and Th II complexes were reported to activate H2, leading to higher-valent hydride complexes, but the corresponding mechanisms remain elusive. The observed H2 splitting reactivity of 2 contrasts with the reported H2 elimination reactivity of the mixed-valent ytterbium hydride complex [{Yb(Cp*)2}2(-H)]. This reverse pathway may be linked to the greater thermodynamic stability of Yb II compared to Lu II .