A. Ider

Crystal structure of TeOF2

Abstract TeOF 2 crystallizes in the monoclinic system (space group P2 1 ) with unit cell parameters a =551.3(1)pm, b =828.9(1)pm, c =530.7(1)pm, β =96.22(2)°, and Z =4. Its crystal structure was solved and refined to R B =0.058 and R wp =0.116 on the basis of a Rietveld analysis of its X-ray powder pattern. Each tellurium atom is surrounded by six anions [4+2] (two oxygen, two fluorine and two other fluorine atoms at much longer distances). Because of the strong stereochemical activity of their lone pairs E , the coordination polyhedra can be described as distorted trigonal bipyramids TeO 2 F 2 E. These polyhedra associated by sharing O corners, form quasi-independent helical chains coiling along b . Te–F weak bonds, connecting the chains, give a 3D character to the structure. Structural relationships with α -TeO 2 have been found and analysed.

Crystal structure of PbTeF6

Abstract PbTeF6 crystallizes with monoclinic symmetry (space group P2 1 c ) and the unit cell parameters a = 462.5(1) pm, b = 1281.2(2) pm, c = 851.9(1) pm, β = 102.36(1)°, Z = 4. Its crystal structure has been solved by a Rietveld analysis of its X-ray powder pattern and refined to the final agreement factors Rb = 0.059 and Rp = 0.073. The PbII and TeIV atoms are respectively seven- and five-fold coordinated and their lone pair E is stereochemically active. By sharing edges, the PbF7E polyhedra constitute infinite zig-zag chains parallel to Ox. These chains are connected to each other by sharing their free corners with the TeF5E polyhedra, one of the corners being non-bridging. Structural relationships with ReO3-type materials are described and analyzed.