Triiodotelluronium Hexafluoroarsenate TeI3[AsF6]. The Crystal Structure of the Hemi SO2 Solvate and the Structure Relation to the Unsolvated Form

TeI [AsF ] is formed from Te, I , and AsF in liquid SO . At room temperature light red crystals of the hemi SO solvate TeI [AsF ] · 0.5 SO are obtained from a saturated solution. The crystal structure (orthorhombic, Pnnm, a=1107.41(2), b=1866.58(3), c=1207.00(2) pm at 123 K, Z =8) consists of pyramidal TeI cations (Te-I = 267 pm), almost regular octahedral [AsF anions and of SO molecules which show disorder for the O atom positions. A remarkable feature of the crystal structure is the arrangement of the TeI ions that are pairwise associated, facing each other with the I atoms and forming large voids between each other. This causes the significantly lower density of TeI [AsF ] · 0.5 SO (3.88 Mgm ) in comparison to the unsolvated form (4.20 Mgm , Pass more 1981).