Synthesis, crystal structure and characterization of a new layered lanthanum(III) diselenite hydrogenselenite: La(Se2O5)(HSeO3)(H2O)·H2O

Reaction of lanthanum(III) chloride and SeO2 under acidic condition lead to a new layered lanthanum(III) diselenite hydrogenselenite, La(Se2O5)(HSeO3)(H2O)·H2O. The title compound crystallizes in the orthorhombic space group Pbca with cell parameters of a = 7.329 (1), b = 11.013 (2), c = 22.802 (3) Å. In the title compound the nine-coordinated lanthanum(III) ions are bridged by Se2O52− and HSeO3− anions to form 2D layers normal to the c-axis. The diselenite anion is hexadentate, forming two types of chelating rings, namely a four-membered Ln-O-Se-O ring and a six-membered La-O-Se-O-Se-O ring, and also bridges with two other La(III) ions. The hydrogenselenite group is bidentate bridging and the protonated oxygen atom remains non-coordinated and is involved in the hydrogen bonding with aqua ligand as well as lattice water molecule.