Revised values of the bond-valence parameters for TeIV—O, TeVI—O and TeIV—Cl

Abstract

Bond-valence parametersr0andbhave been re-determined for TeIV—O:r0= 1.9605 Å,b= 0.41; TeVI—O:r0= 1.921 Å,b= 0.56; and TeIV—Cl:r0= 2.3115 Å,b= 0.555. Bond distance data from 208 independent TeIV—O polyhedra, 118 TeVI—O polyhedra and 26 TeIV—Cl polyhedra were used, and all neighbours out to 3.5 Å were included. Root-mean square deviations of bond-valence sums on Te from ideal values were 0.1934, 0.1939 and 0.0865 v.u. The good fit for TeIV—O over a range of Te coordination numbers from 3 to 12 demonstrates that there is no essential difference in character between short `primary' Te—O bonds, oriented away from the Te lone pair, and longer `secondary' Te—O bonds on the same side of the Te atom as the lone pair. Comparison of bond-valence sums for Te—O polyhedra obtained using the new parameters with those calculated using earlier literature values shows that the new parameters give a narrower spread of calculated bond-valence sums, which means much closer to the formal valence for both oxidation states of tellurium.