KTe3O6F: a new layer TeO2 structure, stuffed with KF units

The crystal structure of a new tellurium IV oxyfluoride: KTe3O6F in the series MTe3O6F (M<f>=</f>K, Rb) has been determined on the basis of X-ray single crystal data (rhombohedral symmetry, R-3 space group, <f>a=948.60(10)</f>, <f>c=1377.4(2)</f> pm, <f>Z=6</f>, refinement program: Shelxl-97, <f>R1=0.037</f>). The structure is based on twisted Te3O6F sheets, separated by K layers, in which TeO4F square pyramids share O corners and edges, forming hexagonal rings of the same nature as in hexagonal bronzes. The F anions are weakly bonded to Te cations (Te&z.sbnd;F<f>=</f>245.3 pm) and form quasi-independent KF units inserted inside a TeO2 layer structure. The E lone pair is stereochemically active.The O<f>/</f>F order in this phase and in other Te IV oxyfluorides is discussed. [ABSTRACT FROM AUTHOR]