Kristallstruktur des Tellurtetrajodids TeJ4

The crystal structure of tellurium tetraiodide TeL was determined from three-dimensional X-ray diffractometer data and was refined by full-matrix least-squares methods to an R index of 5.1%. The crystals are orthorhombic, space group Pnma, with a= 13.635 (5), b= 16.798 (5), c= 14.624 (5)/~, Z= 16TeI4. The structure is built of tetrameric (TeI4)4 molecules which are not isomorphous with the (TeCl4)4 molecular structure, but form a novel binary X4Y16 structure type composed of edge-sharing TeI6 octahedra. Mean Te-I bond lengths are 2.769, 3.108 and 3.232 ,~ for bonds to terminal, doubly and triply bridging iodine atoms, respectively. Intermolecular I . . . I distances as short as 3.870, 3"893, 3.932 ,~ indicate weak bonding interactions between the Te4116 molecules. Within the series of the TeF4, TeCL and TeL crystal structures, a strong decrease of the stereochemical activity of the non-bonding electron pair on tellurium(IV) is observed.