18078-40-5Relevant articles and documents
Polymorphism in alkali metal uranyl nitrates: Synthesis and crystal structure of γ-K(UO2)(NO3)3
Jouffret, Laurent J.,Krivovichev, Sergey V.,Burns, Peter C.
, p. 1475 - 1480 (2011)
Single crystals of γ-K(UO2)(NO3)3 were prepared from aqueous solutions by evaporation. The crystal structure [orthorhombic, Pbca (61), a = 9.2559(3) A, b = 12.1753(3) A, c = 15.8076(5) A, V = 1781.41(9) A3, Z = 8] was determined by direct methods and refined to R1 = 0.0267 on the basis of 3657 unique observed reflections. The structure is composed of isolated anionic uranyl trinitrate units, [(UO2)(NO3)3] -, that are linked through eleven-coordinated K+ cations. Both known polymorphs of K(UO2)(NO3)3 (α-and γ-phases) can be considered as based upon sheets of isolated complex [(UO2)(NO3)3]- ions separated by K+ cations. The existence of polymorphism in the two K[UO2(NO3)3] polymorphs is due to the different packing modes of uranyl trinitrate clusters that adopt the same two-dimensional but different three-dimensional arrangements. Copyright
Crystal structure of K[UO2(NO3)3] and some features of compounds M[UO2(NO3)3] (M = K, Rb, and Cs)
Krivovichev,Burns
, p. 16 - 19 (2004)
Greenish-yellow transparent crystals of K[UO2(NO 3)3] were prepared from aqueous solutions as by-product in synthesis of potassium chromatouranylates. The crystal structure was solved by the direct methods and refined to R1 = 0.037 (wR2 = 0.070) for 1452 reflections with |Fhkl|≥4σ|Fhkl|. Monoclinic system, space group C2/c, a = 13.4877(10), b = 9.5843(7), b = 7.9564(6) A, β = 116.124(2)°, V = 923.45(12) A3. The structure of K[UO2(NO3)3] contains isolated complex ions [UO2(NO3)3]- whose uranyl groups are aligned parallel to the [101] plane. The K + cations, coordinated by twelve oxygen atoms, are located between the complex anions. Comparison of the structure with known data on M[UO 2(NO3)3] compounds (M = K, Rb, Cs) suggests the possibility of phase transitions due to relatively small displacements of [UO2(NO3)3]- anions and K + cations, retaining the general structural motif.
