Hydrogenselenates of rare earth elements: Syntheses and crystal structuresof La(HSeO4)(3) and Gd(HSeO4)(SeO4)

Colorless transparent single crystals of La(HSeO4)(3) (hexagonal, P6(3)/m, Z = 2, a = 971.7(1), c = 616.98(8) pm, R-all = 0.0440) were obtained from t he reaction of La2O3 and cone. selenic acid. La(HSeO4)(3) is isotypic with the corresponding hydrogensulfate. Its structure can be seen as a variant o f the UCl3 type structure with complex anions and contains the La3+ ions in ninefold coordination of oxygen atoms, Single crystals of Gd(HSeO4)(SeO4) crystallize from a solution of Gd2O3 in selenic acid (70% H2SeO4). In the o rthorhombic crystal structure (Pbca, Z = 8, a = 920.4(1), b = 1351.6(2), c = 1004.0(1) pm, R-all = 0.0276) the Gd3+ ions are coordinated by eight oxyg en atoms belonging to four SeO42- and four HSeO4- ions, These are surrounde d by four Gd3+ ions.