Uranyl derivatives: discovering features by comparing related crystal structures.

Three new complexes, namely, hydronium μ-hydroxido-μ-isobutyrato-bis[diaquaberyllium(II)] tris[triisobutyratodioxidouranium(VI)] dihydrate, (H3O)[Be2(C4H7O2)(OH)(H2O)4][U(C4H7O2)3O2]3·2H2O or (H3O)[Be2(μ-OH)(μ-i-but)(H2O)4][UO2(i-but)3]3·2H2O (I) [i-but denotes the isobutyrate ion CH3CH(CH3)COO-], poly[tri-μ4-isobutyrato-di-μ-oxido-rubidium(I)uranium(VI)], [RbU(C4H7O2)3O2]n or Rb[UO2(i-but)3] (II), and poly[pentaaquatetracosa-μ-crotonato-hexadeca-μ-oxido-tetrabarium(II)octauranium(VI)], [Ba4U8(C4H5O2)24O16(H2O)5]n or Ba4[UO2(crt)3]7[UO2(crt)3(H2O)](H2O)4 (III) (crt denotes the crotonate ion, C3H5COO-), were synthesized and their crystal structures were determined. In order to achieve general conclusions, a comparison of the new crystal structures with previously published structures was conducted. Complex I is the first compound containing a hydronium ion and Be atoms in an oxygen environment simultaneously. It was revealed that the new Rb isobutyratouranylate, II, features the same packing motif as in the butyrate-, crotonate- and methacrylate-containing analogues. Using the example of the Rb series of compounds, we evaluated the compliance of the sizes of the structural fragments based upon the change of their crystal system. It was shown that the packing motif of III strongly depends on the ratio of the reagents.