Li3UHO3: A Uranium Hydride Oxide.

Li3UHO3, the first crystallographically characterized uranium hydride oxide (oxyhydride), was synthesized via a salt-flux reaction of UO2 with excess LiH at 973 K as a brown, air-sensitive solid. Single-crystal X-ray diffraction reveals a novel coloring variant of the rocksalt structure (Pm3m) in which oxide and hydride anions form a cubic close-packing and U4+/Li+ cations fill alternating octahedral voids. The edge-sharing [LiH2O4] and [UO6] octahedra yield ordered anion positions. Li-O distances are consistent with related hydride oxides, whereas Li-H separations are unusually long, reflecting weaker hydride coordination within edge-sharing octahedra. 1H/7Li MAS NMR and CHN analyses confirm H- incorporation. Li3UHO3 thus extends heteroanionic hydride chemistry into the actinide series.