Neutron diffraction study of Rb2UO2(SeO4)2 • 2D2O

A powder of deuterated rubidium diselenatouranylate dihydrate Rb2UO2(SeO4)(2) center dot 2D(2)O has been studied by neutron diffraction. The compound is orthorhombic, space group Pna2(1), with the following unit cell parameters: a = 13.654(2) , b = 11.863(2) , c = 7.625(1) , Z = 4, R (F) = 3.77, R (I) = 6.12, and chi(2) = 2.21. Basic structure units are [UO2(SeO4)(2) center dot D2O](2-) layers belonging to the AB (2) (2) M-1 crystal-chemical group (A = UO (2) (2+) , B-2 = SeO (4) (2-) , M-1 = D2O) of uranyl complexes. The hydrogen atoms if the water molecules involved in the layer form intralayer hydrogen bonds with the terminal oxygen atoms of selenate ions. The outer-sphere water molecules are coordinated to the rubidium ions and are involved in hydrogen bonding with oxygen atoms of neighboring [UO2(SeO4)(2) center dot D2O](2-) layers.