Vladislav V. Klepov

Trinuclear {Sr[UO2L3]2(H2O)4} and pentanuclear {Sr[UO2L3]4}2− uranyl monocarboxylate complexes (L-acetate or n-butyrate ion)

Crystals of two acetate complexes, Cs2{Sr[UO2L3]4} (1) and [Sr(H2O)6][UO2L3]2{Sr(H2O)4[UO2L3]2}2 (2), and one n-butyrate complex, {Sr(H2O)4[UO2L3]2}·2H2O (3), of uranium(VI), where L is a corresponding monocarboxylate ion, were studied by means of FTIR spectroscopy and single crystal X-ray analysis. The structure of 1 contains pentanuclear anionic complexes, {Sr[UO2L3]4}2−, bonded in a three dimensional framework by electrostatic interactions with Cs+ cations. The structure of 2, in addition to ‘typical’ uranyl triacetate complexes of [UO2L3]− and [Sr(H2O)6]2+ cations, contains neutral trinuclear complexes, {Sr(H2O)4[UO2L3]2}. The structure of 3 with n-butyrate ions consists of neutral complexes of {Sr(H2O)4[UO2L3]2} and molecules of crystallized water. Analysis of intermolecular interactions in 2 and 3 by means of two independent approaches (molecular Voronoi–Dirichlet polyhedra and molecular Hirshfeld surfaces) revealed that discrete complex groups are connected with one another mostly due to H/O hydrogen bonds and H/H dispersion interactions. A dynamic balance among mono- and poly-nuclear complexes in aqueous solutions containing R2+ and [UO2L3]− ions is proposed. The effect of the alkyl chain and the nature of the R2+ cation on the balance is discussed.

Th(AsIII4AsV4O18): a Mixed-Valent Oxoarsenic(III)/arsenic(V) Actinide Compound Obtained under Extreme Conditions

A high-temperature/high-pressure method was employed to investigate phase formation in the Th(NO3)4·5H2O-As2O3-CsNO3 system. It was observed that an excess of arsenic(III) in starting system leads to the formation of Th(As(III)4As(V)4O18), which is representative of a rare class of mixed-valent arsenic(III)/arsenic(V) compounds. This compound was studied with X-ray diffraction, energy-dispersive X-ray, and Raman spectroscopy methods. Crystallographic data show that Th(As(III)4As(V)4O18) is built from (As(III)4As(V)4O18)(4-) layers connected through Th atoms. The arsenic layers are found to be isoreticular to those in previously reported As2O3 and As3O5(OH), and the geometric differences between them are discussed. Bands in the Raman spectrum are assigned with respect to the presence of AsO3 and AsO4 groups.

Crystal structure of R[UO2(CH3COO)3] (R = NH4+, K+, or Cs+)

The single crystal structure of NH4[UO2(CH3COO)3] (I), K[UO2(CH3COO)3] (II), and Cs[UO2(CH3COO)3] (III) is studied by X-ray diffraction. I and II crystallize in the tetragonal crystal system. The crystal data are as follows: a = 13.6985(3) and c = 27.5678(14) Å, V = 5173.1(3) Å3, space group I41/a, Z = 16, and R = 0.023 for I; a = 13.8890(5) and c = 26.0839(18) Å, V = 5031.7(4) Å3, space group I41/a, Z = 16, and R = 0.037 for II. Crystals III are orthorhombic, a = 18.176(2), b = 13.119(2), and c = 22.088(4) Å, V = 5267(1)Å3, space group Pbca, Z = 16, and R = 0.0424. In structures I–III, the uranium-containing structural units are represented by discrete mononuclear [UO2(CH3COO)3]− groups, which belong to the AB301 (A = UO22+, B01=CH3COO−) crystal chemical group of uranyl complexes.

Synthesis, structure, and properties of [Be(H2O)4][UO2(CH3COO)3]2

Crystals of previously unknown compound [Be(H2O)4][UO2(CH3COO)3]2 were prepared and studied by X-ray diffraction analysis. The compound crystallizes in the tetragonal system, unit cell parameters (at 100 K): a = 10.3647(3), c = 23.4127(8) Å, V = 2515.16(13) Å3, space group I41/a, Z = 4, R = 0.0194. The structure consists of mononuclear complexes [Be(H2O)4]2+ and [UO2(CH3COO)3]− linked with each other by electrostatic interactions and hydrogen bonds formed by water molecules and O atoms of acetate anions. The compound was also studied by methods of thermal analysis and IR spectroscopy.

Morphotropy and Temperature-Driven Polymorphism in A2Th(AsO4)2 (A = Li, Na, K, Rb, Cs) Series

A new alkaline thorium arsenate family was obtained and systematically investigated. The structures of A2Th(AsO4)2 (A = Li, Na, K, Rb, Cs) were determined from single crystal X-ray diffraction data. Li2Th(AsO4)2 and either isostructural K2Th(AsO4)2 and Rb2Th(AsO4)2 crystallize in the monoclinic crystal system. Na2Th(AsO4)2 and Cs2Th(AsO4)2 crystallize in the orthorhombic and tetragonal crystal systems, respectively. Li2Th(AsO4)2 consists of [Th(AsO4)2](2-) layers with Li atoms in the interlayer space. The rest of the compounds are based on 3D frameworks. Differences in local environments of ThO8 coordination polyhedra are described in relation to the symmetry. Despite different local environments of ThO8 coordination polyhedra and different structural symmetry, underlying nets of A2Th(AsO4)2 (A = Na, K, Rb, Cs) were shown to be the same. Single-crystal and powder Raman spectra were measured, and bands are assigned. DSC measurements showed phase transitions in K2Th(AsO4)2 and Rb2Th(AsO4)2, which were studied using high-temperature powder X-ray diffraction (HT-PXRD). The data of HT-PXRD demonstrates two high-temperature polymorphic modification of K2Th(AsO4)2 and only one for the isotypic Rb2Th(AsO4)2. The phase transitions in both K and Rb phases are reversible.

Synthesis and X-ray diffraction study of (Cs0.5Ba0.25)[UO2(CH3COO)3] and Ba0.5[UO2(CH3COO)3]

Uranyl triacetate complexes (Cs{sub 0.5}Ba{sub 0.25})[UO{sub 2}(CH{sub 3}COO){sub 3}] (I) and Ba{sub 0.5}[UO{sub 2}(CH{sub 3}COO){sub 3}] (II) are synthesized for the first time and their structures are determined by X-ray diffraction. Both compounds crystallize in the cubic crystal system. The crystal data are as follows: a = 17.3289(7) Angstrom-Sign , V = 5203.7(4) Angstrom-Sign {sup 3}, space group I2{sub 1}3 and Z = 16 (I); a = 17.0515(8) Angstrom-Sign , V = 4957.8(4) Angstrom-Sign {sup 3}, space group I 4 bar 3d, and Z = 16 (II). In I and II, as in all uranyl triacetates studied earlier, the coordination polyhedron of the uranium atom is a hexagonal bipyramid whose vertices are occupied by the oxygen atoms of the uranyl and three acetate groups. The uranium-containing group belongs to the AB{sub 3}{sup 01} (A = UO{sub 2}{sup 2+}, B{sup 01} = CH{sub 3}COO{sup -}) crystal chemical group of uranyl complexes. It was found that compound II is isostructural to the (Rb{sub 0.50}Ba{sub 0.25})[UO{sub 2}(CH{sub 3}COO){sub 3}] studied earlier.AbstractUranyl triacetate complexes (Cs0.5Ba0.25)[UO2(CH3COO)3] (I) and Ba0.5[UO2(CH3COO)3] (II) are synthesized for the first time and their structures are determined by X-ray diffraction. Both compounds crystallize in the cubic crystal system. The crystal data are as follows: a = 17.3289(7) Å, V = 5203.7(4) Å3, space group I213 and Z = 16 (I); a = 17.0515(8)Å, V = 4957.8(4) Å3, space group I

Crystal structure of PbUO2(CH3COO)4(H2O)3

nbar 4n

First uranyl methacrylate complexes: Synthesis and structure

3d, and Z = 16 (II). In I and II, as in all uranyl triacetates studied earlier, the coordination polyhedron of the uranium atom is a hexagonal bipyramid whose vertices are occupied by the oxygen atoms of the uranyl and three acetate groups. The uranium-containing group belongs to the AB301 (A = UO22+, B01 = CH3COO−) crystal chemical group of uranyl complexes. It was found that compound II is isostructural to the (Rb0.50Ba0.25)[UO2(CH3COO)3] studied earlier.