Structure of uranium borate UB2O6

Mr=355.71, monoclinic, C2/c, a=12.504(3), b=4.183(1), c=10.453(3) A, β=122.18(3)0, V=462.7(8) A3, Z=4, Dx=5.10 Mg m-3, λ(Mo Kα)=0.7107 A, μ=33.7 mm-1, F(000)=600, T=290 K; 1707 contributing reflexions, R(F)=0.066, wR=0.082. This compound has a true lamellar structure with neutral layers held together by van der Waals forces between oxygen atoms (O-O 2.91 A). Inside the layers U6+ has a uranyl bond (U-O 1.75 A) perpendicular to four other neighbours (U-O 2.38-2.49 A) and these polyhedra are shared by opposite edges. B atoms are in BO3 triangles (B-O 1.32-1.39 A) which lie in chains between the UO6 octahedra arrays. (orig.)