Molten salt flux synthesis and structure of the new layered uranyl tellurite, K4[(UO2)5(TeO3)2O5]

The reaction of UO3 and TeO3 with a KCI flux at 800 degrees C for 3 days yields single crystals of K-4[(UO2)(5)(TeO3)(2)O-5]. The structure of the title compound consists of layered, two-dimensional (2)(infinity)[(UO2)(5)(TeO3)(2)O-5](4-) sheets arranged in a stair-like topology separated by potassium cations. Contained within these sheets are one-dimensional uranium oxide ribbons consisting of UO7 pentagonal bipyramids and UO6 tetragonal bipyrarnicls. The ribbons are in turn linked by corner-sharing with trigonal pyramidal TeO3 units to form sheets. The lone-pair of electrons from the Te03 groups are oriented in opposite directions with respect to one another on each side of the sheets rendering each individual sheet nonpolar. The potassium cations form contacts with nearby tellurite units and axial uranyl oxygen atoms. Crystallographic data (193 K, MoK alpha, lambda = 0.71073 angstrom): triclinic, space group P (1) over bar, a = 6.8514(5) angstrom, b = 7.1064(5)angstrom, = 11.3135(8)angstrom, = 99.642(1)degrees, beta= 93.591(1)degrees, gamma = 100.506(1)degrees, V = 531.48(7) A(3), Z = 1, R(F) = 4.19% for 149 parameters and 2583 reflections with I > 2 sigma(I). (c) 2005 Elsevier Inc. All rights reserved.