f-Element/crown ether complexes, 11. Preparation and structural characterization of [UO2(OH2)5] [ClO4]2·3(15-crown-5)·CH3CN and [UO2(OH2)5] [ClO4]2·2(18-crown-6)·2 CH3CN·H2O

The reaction of UO₂(ClO₄)·nH₂O with 15-crown-5 and 18-crown-6 in acetonitrile yielded the title complexes. UO₂(OH₂)₅] ClO₄]₂·3(15-crown-5)·CH₃CN crystallizes in the triclinic space groupPT with (at–150°C)a=8.288(6),b=12.874(7),c=24.678(7) Å, =82.62(4), =76.06(5), =81.06(5)°, andD _calc=1.67 g cm^–3 forZ=2 formula units. Least-squares refinement using 6248 independent observed reflections F _o5(F _o)] led toR=0.111. UO₂(OH₂)₅] ClO₄]₂·2(18-crown-6)·2CH₃CN·H₂O is orthorhombicP2₁2₁2₁ with (at–150 °C)a=12.280(2),b=17.311(7),c=22.056(3) Å,D _calc=1.68 g cm^–3,Z=4, andR=0.032 (3777 observed reflections). In each complex the crown ether molecules are hydrogen bonded to the water molecules of the pentagonal bipyramidal UO₂(OH₂)₅]²⁺ ions, each crown ether having exclusive use of two hydrogen atoms from one water molecule and one hydrogen from another water molecule. In the 15-crown-5 complex the remaining hydrogen bonding interaction is between one of the water molecules and one of the perchlorate anions. The solvent molecule has a close contact between the methyl group and a perchlorate anion suggesting a weak interaction. There are a total of three U-OH...OClO₃ hydrogen bonds to the two perchlorate anions in UO₂(OH₂)₅] ClO₄]₂·(18-crown-6)·2CH₃CN ·H₂O. The remaining coordinated water hydrogen bond is to the uncoordinated 2H₂O molecule, which in turn is hydrogen bonded to a perchlorate oxygen atom and an acetonitrile nitrogen atom. One solvent methyl group interacts with an anion, the other with one of the 18-crown-6 molecules. Unlike the 15-crown-5 structure, the hydrogen bonding in this complex results in a polymeric network with formula units joined by hydrogen bonds from one of the solvent molecules and the uncoordinated water molecule. Supplementary data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82051 (37 pages).For Part 10, see reference 1].