The crystal structure of a new CdTe(2)O(5) polymorph, isotypic with ∊-CaTe(2)O(5)

Single crystals of cadmium penta­oxidoditellurate(IV), CdTe(2)O(5), were obtained as by-products in a hydro­thermal reaction of Cd(NO(3))(2)·4H(2)O, TeO(2), H(6)TeO(6) and NH(3) (molar ratios 2:1:1:6) at 483 K for seven days. The crystals represent a different polymorph (henceforth referred to as the β-form) than the α-CdTe(2)O(5) crystals grown from the melt, and are isotypic with hydro­thermally grown ∊-CaTe(2)O(5). The asymmetric unit of β-CdTe(2)O(5) comprises one Cd, two Te and five O sites, all of which are located in general positions (Wyckoff position 4 e). The cadmium(II) atom is coordinated by seven oxygen atoms, forming (2) (∞)[CdO(6/2)O(1/1)] (100) layers. Both tellurium sites are surrounded by four oxygen atoms with one of them being at a significantly longer distance than the other three. The resulting bis­phenoidal [TeO(4)] units also form layers propagating parallel to (100) by sharing edges with each other. The stereochemically active 5s (2) lone pair of the Te(IV) atoms leads to the formation of large channels extending along [011] and smaller ones along [010]. A qu­anti­tative comparison between the crystal structures of β-CdTe(2)O(5) and ∊-CaTe(2)O(5) is made.