Neutron diffraction study of uranyl oxalate [UO2(C2O4)(D2O)] • 2D2O

A powdered sample of uranyl oxalate [UO2(C2O4)(D2O)] center dot 2D(2)O (compound I) is studied using neutron diffraction. The crystals are monoclinic, space group P2(1)/c, with a = 5.608(1) angstrom, b = 17.016(3) angstrom, c = 9.410(2) angstrom, beta = 98.9369(2)degrees, Z = 4, R-F = 0.042, R-I = 0.054, chi(2) = 1.5. The main structural units of the crystals are [UO2(C2O4)(D2O)] chains. These chains, which belong to the AKO(2)M(1) (A = UO2 (2+)) crystal-chemical group of the uranyl complexes, lie parallel to [101]. The water molecules in the crystals of I are hydrogen-bonded into zigzag chains running along [100]. Since each third oxygen atom of the chain formed of water molecules is coordinated to the uranium atom, the uranyl oxalate chains are linked into {[UO2(C2O4)(D2O)] center dot 2D(2)O} layers that lie normal to [010]. The layers are linked into the framework through interlayer hydrogen bonds (D2O)O-D center dot center dot center dot O (oxalate).