Crystal structure of Sr5Te4O12(OH)2, the first basic strontium oxotellurate(IV)

Abstract

The asymmetric unit of the title basic strontium oxotellurate(IV), Sr5Te4O12(OH)2{systematic name pentastrontium tetrakis[oxotellurate(IV)] dihydroxide}, comprises three SrIIcations (one with site symmetry 2) and two TeIVatoms, as well as seven O atoms. The coordination numbers of the alkaline earth cations to nearby O atoms range from seven (2 ×) to eight, and the TeIVatoms are surrounded by three oxygen partners in the form of trigonal pyramids. The SrOxpolyhedra share corners and edges to build up a three-dimensional framework structure encapsulating channels propagating along [010]. The TeIVatoms flank the framework O atoms and are situated at the outer array of the channels with the 5s2lone electron pairs protruding into the empty space of the channels (diameter ≃ 4 Å). Although the H atom of the OH group could not be located, bond-valence-sum calculations and typical O...O distances (range 2.81–3.06 Å) clearly indicate hydrogen bonding of medium to weak strengths.