Synthesis and crystal structures of the layered uranyl tellurites A2[(UO2)3(TeO3)2O2] (A = K, Rb, Cs)

The reactions Of UO3 and TeO3 with KCl, RbCl, or CsCl at 800 degreesC for 5 d yield single crystals of A(2)[(UO2)(3)(TeO3)(2)O-2] (A = K (1), Rb (2), and Cs (3)). These compounds are isostructural with one another, and their structures consist of two-dimensional 2infinity[(UO2)(3)(TeO3)(2)O-2](2-) sheets arranged in a stair-like topology separated by alkali metal cations. These sheets are comprised of zigzagging uranium(VI) oxide chains bridged by corner-sharing trigonal pyramidal TeO32- anions. The chains are composed of 3 dimeric, edge-sharing, pentagonal bipyramidal UO7 Moieties joined by edge-sharing tetragonal bipyramidal UO6 units. The lone-pair of electrons from the TeO3 groups are oriented in opposite directions with respect to one another on each side of the sheets rendering each individual sheet non-polar. The alkali metal cations form contacts with nearby tellurite oxygen atoms as well as with oxygen atoms from the uranyl moieties. Crystallographic data (193 K, MoKalpha, lambda = 0.7107 Angstrom): 1, triclinic, space group P (1) over bar, a = 6.7985(5) b = 7.0123(5) Angstrom, c = 7.8965(6) Angstrom, alpha = 101.852(1)degrees, beta = 102.974(1)degrees, gamma = 100.081 (1)degrees, V = 349.25(4) Angstrom(3), Z = 2, R(F) = 2.70% for 98 parameters and 1697 reflections with I > 2sigma(I); 2, triclinic, space group P (1) over bar, a = 7.0101(6) Angstrom, b = 7.0742(6) Angstrom, c = 8.0848(7) Angstrom, alpha = 105.590(2)degrees, beta = 10 1.760(2)degrees, gamma = 99.456(2)degrees, V = 367.91(5) Angstrom(3), Z = 2, R(F) = 2.36% for 98 parameters and 1817 reflections with I > 2sigma(I); 3, triclinic, space group P (1) over bar, a = 7.0007(5) Angstrom, b = 7.5195(6) Angstrom, c = 8.4327(6) Angstrom, alpha = 109.301 (1)degrees, 3 beta =100.573(1)degrees, gamma = 99.504(1)degrees, V = 399.49(5) Angstrom(,)(3) Z = 2, R(F) = 2.61% for 98 parameters and 1965 reflections with I > 2sigma(I). (C) 2004 Elsevier Inc. All rights reserved.