Synthese und Kristallstruktur von Te₈O₁₀(PO₄)₄

Abstract

Octatellurium(IV)decaoxide tetraorthophosphate, Te₈O₁₀(PO₄)₄, has been synthesized for the first time. Single crystals of the compound have been obtained from the oxides TeO₂ and P₂O₅ by chemical transport reaction at 550°C. The crystals are monoclinic, space group P2₁/n, with a = 20.076, b = 4.650, c = 11.220 Å, β = 92.99° and Z = 2. The crystal structure has been determined by direct methods using three-dimensional x-ray diffraction data and refined by a least-squares method to R = 4.9%. The crystal structure comprises “Zweier-Dreifachketten” (triple chain) 3_∞¹[Te₆O₁₀]⁴⁺ (average Te–O distances 1.954 Å) which are connected with an other tellurium atom over the terminal oxygen atoms (Te–O = 1.896 Å). The tellurium atom, itself, is strongly bonded to three orthophosphate groups by covalent Te–O(→P) bonds (1.945, 2.092, 2.104 Å). This leads to band-like structural units [Te₆O₁₀] [Te(PO₄)₂]₂, which are connected with each other over the non-bonded oxygen atoms of the orthophosphat groups thus forming puckered layers [Te–O(→P) = 2.201, 2.288 Å]. The layers themselves are held together by weak interaction between the oxygen atoms of the orthophosphate groups and the tellurium atoms of the adjacent layer [Te…O(→P) = 2.653, 2.870 Å].