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The crystal structure of bis (1, 1, 1, 5, 5, 5 hexafluoropentane 2,4 dionato) dioxo ammonia uranium(VI)

1979; Pergamon Press; Volume: 41; Issue: 6 Linguagem: Inglês

10.1016/0022-1902(79)80274-2

1878-1225

D.A. Johnson, J.C. Taylor, A.B. Waugh,

Lanthanide and Transition Metal Complexes

The crystal structure of bis(1,1,1,5,5,5 hexafluoropentane 2,4 dionato) dioxo ammonia uranium(VI) or UO2(HFA)2NH3, has been determined by single crystal X-ray diffraction. The thin yellow platelets crystallise in the C-centred monoclinic system with a = 6.665(1), b = 24.428(4), c = 5.613(2) Å, β = 92.964(5)°, with 2 molecules per unit cell. Possible space groups are C2, Cm or C2m. Structure analysis confirmed Cm. A refinement involving 815 independent reflections was used, and the final R factor was 0.098. The structure is molecular, and the uranium atom has pentagonal bipyramidal coordination, the pentagonal ring being made up of four oxygen atoms from two bidentate (HFA) units and the nitrogen atom of the ammonia. Molecules are bound into sheets normal to the b-axis by hydrogen bonding involving the ammonia, the sheet structure being consistent with the plate-like morphology. Uranyl distances are both 1.69(5) Å, UO (carbonyl) distances are 2.47(4) and 2.32(3) Å and the UN distance is 2.48(6) Å. The uranyl group is linear and normal to the pentagonal coordination plane. The (HFA) groups have a dihedral angle of 15.3° to this plane. As in many other (HFA) complexes the fluorine atoms in the CF3 groups are disordered.