Crystal structure of complexes of Np(VI) and Pu(VI) perchlorates with triphenylphosphine oxide, [NpO2(OP(C6H5)3)4](ClO4)2 and [PuO2(OP(C6H5)3)4](ClO4)2

Single crystals of [NpO₂(TPPO)₄](ClO₄)₂ and [PuO₂(TPPO)₄](ClO₄)₂ isostructural to the complex [UO₂(TPPO)₄](ClO₄)₂ [TPPO = OP(C₆H₅)₃] studied previously were prepared, and the structures of these compounds were determined. The coordination polyhedron of these compounds is a tetragonal bipyramid. The geometric characteristics of the tetragonal bipyramids in the compounds are practically the same despite the actinide contraction of the central atoms, whereas the unit cell volume decreases in the series U-Np-Pu. The equality of the volumes of the coordination polyhedra of the U, Np, and Pu atoms is attributed to the influence of TPPO containing phenyl radicals with negative effective charge. Original Russian Text ? I.A. Charushnikova, N.N. Krot, Z.A. Starikova, I.N. Polyakova, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 5, pp. 407–411.     

Synthesis and characteristics of double Np(VI) and Pu(VI) phthalates of the composition M2AnO2(C8H4O4)2· n H2O (M = NH4, K, and Cs)

Double salts of o-phthalic acid of the general composition M₂AnO₂(C₈H₄O₄)₂ nH₂O (M = NH₄, K, Cs and An = Pu, Np) were isolated from neutral aqueous solutions. The composition was determined by chemical analysis. The compounds were characterized by powder X-ray diffraction, and unit cell parameters of some salts were determined from the powder X-ray patterns. The optical absorption spectra of the crystal-line plutonium compounds were measured. Thermal behavior in heating to 800°C in air was studied. The differences in the behavior of U, Np, and Pu compounds under similar conditions were noted. Original Russian Text N.N. Krot, I.A. Charushnikova, A.A. Bessonov, M.S. Grigor’ev, 2007, published in Radiokhimiya, 2007, Vol. 49, No. 3, pp. 202–206.     

Complexes of Np(VI) with Cyclobutanecarboxylic Acid Anions and Single-Charged Cations in the Outer Sphere: [NH4][NpO2(cbc)3], [C(NH2)3][NpO2(cbc)3], and [N(CH3)4][NpO2(cbc)3]

Radiochemistry - Three new Np(VI) complexes with cyclobutanecarboxylic acid anions and single-charged outer-sphere anions: ammonium, [NH4][NpO2(cbc)3] (I), guanidinium, [C(NH2)3][NpO2(cbc)3] (II),...     

Crystal Structure of An(VI) Complexes with Succinate Anions, [PuO2(C4H4O4)(H2O)] and Cs2[(AnO2)2(C4H4O4)3]·H2O (An = U,Np, Pu)

Radiochemistry - Actinide(VI) complexes with succinate anions [PuO2(succ)(H2O)] and Cs2[(AnO2)2(succ)3]·H2O (An = U, Np, Pu), where succ = [C4H4O4]2 ?, were synthesized and studied by...     

Synthesis and crystal structure of americium(V) dichromate, Cs3AmO2(Cr2O7)2·H2O

A new Am(V) chromate complex with outer-sphere cesium cation, Cs₃AmO₂(Cr₂O₇)₂·H₂O, was prepared from aqueous solution. Its composition and structure were determined by single crystal X-ray diffraction. The Am(V) atom has coordination surrounding in the form of a distorted pentagonal bipyramid with the O atoms of the AmO ₂ ⁺ group in apical positions. The equator of the bipyramid is formed by the O atoms of four dichromate groups and of the water molecule. The mean bond lengths (Å) are as follows: Am=O 1.802(5), Am-O(Cr₂O₇) 2.443(6), and Am-O_w 2.519(6). The Am(V) pentagonal bipyramids are combined via bidentate bridging Cr₂O ₇ ^2? anions into infinite chains [AmO₂(Cr₂O₇)₂H₂O] _n ^3? arranged in layers parallel to the series of diagonal planes (111). A system of hydrogen bonds links the chains in a layer and the layers with each other. The Cs cations are arranged between the layers, forming cationic interlayers.     

Selective Recovery of Chromium from Precipitates Containing d Elements and Actinides: II. Effect of H2O2

Oxidation of various Cr(III) hydroxides and mixed Cr(III)-Ni(II) and Cr(III)-Fe(III) hydroxides with hydrogen peroxide was studied. The initial reaction rate increases as the Cr(III) content in the suspension and H₂O₂ concentration are increased and nonmonotonicaly decreases with increasing NaOH concentration within the 0.2-2.0 M range. The activation energy in 0.5 M NaOH is equal to 82 kJ mol^{- 1} (30-90°C). The oxidant consumption substantially exceeds the stoichiometry.     

Synthesis and study of new complex Pu(V) and Np(V) acetates

Double Pu(V) and Np(V) acetates of the compositions BaPuO₂Ac₃·2H₂O and SrAnO₂Ac₃·3H₂O with An = Pu and Np were synthesized in a well-crystallized form. In the dry state the compounds are stable in prolonged storage and are not hygroscopic. The plutonyl(V) and neptunyl(V) salts of the similar composition are isostructural. The IR spectra of the compounds were measured, and their behavior in heating was studied.     

Behavior of uranyl malonate in concentrated acetic acid under hydrothermal conditions

Prolonged heating of the malonate UO₂(OOC)₂CH₂·3H₂O at 165°C under a layer of concentrated acetic acid yields the acetate [UO₂(OOCCH₃)₂·HOOCCH₃]₂ (I). In electrically neutral dimer I, the U atom (coordination number 7) is surrounded by chelating acetate ion [average U-O bond length 2.452(3) Å], an HOOCCH₃ molecule [U-O bond length 2.391(3) Å], and a bidentate-bridging acetate ion [average U-O bond length 2.326(3) Å]. An essential difference of I from the previously studied dimier of the similar composition consists in a turn of the HOOCCH₃ molecule, so that a two-dimensional network of strong hydrogen bonds, linking the dimers in layers perpendicular to the [100] direction, is formed in the crystal.     

Structure of the double formate KNpO<Subscript>2</Subscript>(OOCH)<Subscript>2</Subscript>

KNpO₂(OOCH)₂ was isolated from neutral Np(V) solutions with a high concentration of potassium formate. The crystal structure of this compound was determined. The structure consists of infinite anionic chains [NpO₂(OOCH)₂] _n ^n? . Potassium cations are located between these chains. The Np coordination polyhedron is a hexagonal bipyramid whose equatorial plane is formed by the oxygen atoms of four HCOO^? ions. The Np bipyramids in the chains are bound via common equatorial edges. The anionic chains in the structures of KNpO₂(OOCH)₂ and NH₄NpO₂(OOCH)₂ studied previously have similar composition but different structure.     

Double Np(V) Malonates with Co(NH3)6 3 + in the Outer Sphere

Light yellow crystalline products of the general formula Co(NH₃)₆(NpO₂L)₂A·xH₂O, where A = Cl, NO₃, or ClO₄, are precipitated with Co(NH₃)₆ ^{3 +} ions from weakly acidic chloride, nitrate, and perchlorate solutions of Np(V), containing up to 0.3 M CH₂(COO)₂ ^{2 -} (L^{2 -}). When only malonate ions are present in the solution, Np(V) precipitates in the form of Co(NH₃)₆(NpO₂L)₂HL·H₂O. These compounds are virtually insoluble in water and have similar X-ray patterns. Unlike oxalate and phthalate solutions, complex neptunyl(V) ion NpO₂L₂ ^{3 -} is not precipitated with Co(NH₃)₆ ^{3 +} ions from malonate media of the above composition.