CRYSTAL-STRUCTURE OF TE2O3F2

Te2O3F2 crystallizes with the triclinic symmetry (space group P-l) and the unit cell parameters a = 515.3(1) pm, b = 625.7(1) pm, c = 688.8( 1) pm, alpha = 98.71(1)degrees, beta = 110.31(1)degrees, gamma = 92.72 (1)degrees, Z = 2, Its structure was solved and refined to R values R( 1) = 0.024 and wR(2) = 0.059 on the basis of 699 independent reflectio ns recorded on a single crystal with an automatic four-circle diffract ometer, The two Te atoms are, respectively, fourfold and fivefold coor dinated and their lone pair E is stereochemically active, The bond val ence calculation shows a perfect O/F order. The Te(1)O(3)FE and Te(2)O (4)FE polyhedra form, by sharing O-O edges, bipolyhedral units with a very short Te-Te distance (319 pm), These units, by sharing corners, c onstitute independent sheets parallel to x0y, All the F atoms are nonb ridging and orientated, together with the lone pairs E, toward the int erlayer space, The structural relationships with the alpha-TeO2 struct ure have been evidenced and analyzed. (C) 1996 Academic Press, Inc.