Neodymium Diselenite Selenious Acid Dihydrate: Structure and Conformation of the Se₂O₅ Group

The title compound, Nd₂(Se₂O₅)₃.H₂SeO₃.2H₂O, is a new rare earth hydrogen selenite. Its crystal structure is built up of polar layers parallel to the ab plane. Each layer is formed by edge-sharing NdO₉ polyhedra and bridging diselenite groups. Selenious acid and water molecules occur on only one side of the layer. The other side contains flanking diselenite groups only. A complex network of hydrogen bonds holds the layers together. The configuration of Se₂O₅ is defined and compared with the diselenite moieties of related compounds.

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