Crystal structure of dilead tritellurate(IV)

Abstract

The crystal structure of the title compound has been determined by the heavy-atom method from 1 059 reflections, measured with a diffractometer and refined by full-matrix least-squares methods to R 0.105. Crystals are orthorhombic, space group Amam, with unit-cell dimensions a= 18.83(2), b= 7.14(1), c= 19.37(2)Å, and Z= 12. In the structure two of the crystallographically independent tellurium atoms are linked into endless chains parallel to the a axis by bridging oxygen atoms, and the other two are linked into isolated [Te₃O₈]^4– ions. The co-ordination of the tellurium atoms can be considered to be based on a tetrahedral arrangement of three oxygen atoms and a lone pair of electrons, or a trigonal-bipyramidal arrangement of four oxygen atoms and the lone pair. The irregular co-ordination of the lead atoms can also be attributed to lone-pair effects.