A Spectrophotometric Study of the Interaction of Uranyl Ions with Orthosilicic Acid and Polymeric Silicic Acids in Aqueous Solutions

The interaction of UO ₂ ²⁺ ions with orthosilicic acid Si(OH)₄ and polymeric silicic acids (PSAs) was studied spectrophotometrically. The equilibrium constant of the reaction UO ₂ ²⁺ + Si(OH)₄ = UO₂OSi(OH) ₃ ⁺ + H⁺ in solutions with the ionic strength I = 0.1–0.2 is log K = −2.56±0.09 (log K ⁰ = −2.29±0.09 recalculated to I = 0); the stability constant of the complex UO₂OSi(OH) ₃ ⁺ (I = 0) is log β⁰ = 7.52±0.09. Formation of small oligomers (degree of polymerization n ≤ 4) has virtually no effect on the apparent constant K. When high polymers are formed (n > 100), the apparent equilibrium constant decreases by a factor of 2–3, and the “true” equilibrium constant recalculated to the actual concentration of silanol groups increases by a factor of 3–4. The absorption spectrum of the complex UO₂OSi(OH) ₃ ⁺ was obtained by treatment of the experimental spectra; it has an absorption maximum in the visible range at 422.5 nm, ɛ_422.5 = 35±2 l mol⁻¹ cm^{− 1}. At pH higher than 5–6, complexes of UO ₂ ²⁺ with PSAs of the composition UO₂(≡SiO)₂(≡ SiOH) _{m − 2} are formed. The absorption spectrum of such a complex was obtained.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 315–321.Original Russian Text Copyright © 2005 by Yusov, Fedoseev.     

Complexation of Np(V) with Silicate Ions

It was shown that Np(V) forms complexes with anions of orthosilicic acid and other silicate ions at pH higher than 8–8.5. At pH < 9.5, the reaction is mainly described by the equation NpO ₂ ⁺ + OSi(OH) ₃ ⁻ ⇄ NpO₂OSi(OH)₃; the stability constant of the NpO₂OSi(OH)₃ complex is equal to log β₁ = 2.1 ± 0.3. Thus, interaction is weak and hardly significant under real conditions. Carbonate ions in equilibrium with air at pH > 8.5 are the substantially stronger ligands for NpO ₂ ⁺ , and in their presence it is impossible to reveal Np(V) complexation with silicate ions.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 39–43.Original Russian Text Copyright © 2005 by Yusov, Fedoseev, Isakova, Delegard.     

Oxidation of U(IV) in HNO<Subscript>3</Subscript> Solutions Containing Urea and Tc(VII)

The kinetics of U(IV) oxidation with nitric acid in aqueous solutions containing urea, catalyzed with technetium ions, were studied by sampling with subsequent colorimetric determination of the U(IV) concentration. At the constant ionic strength of the solution μ = 2 in the range of the initial concentrations of U(IV) from 2 × 10⁻³ to 1.28 × 10⁻², Tc(VII) from 5 × 10⁻⁵ to 1 × 10⁻³, urea from 0.01 to 0.1, and hydrogen ions from 0.4 to 1.96 M, the reaction rate is described by the equation -d[U(IV)]/dt = k ₁[U(IV)][Tc]^0.5[CO(NH₂)₂] × {[H⁺]² + β₁[H⁺] + β₂}⁻¹ - k ₂[U(IV)]₂[H⁺]^0.4[CO(NH₂)₂]^1.6{ [H⁺]² + β₁[H⁺]+ β₂}⁻², where k ₁ = 172 ± 10 mol^0.5 l^−0.5 min⁻¹ and k ₂ = (9.4±1.2)×10² mol l⁻¹ min⁻¹ at 25°C, β₁ and β₂ are the hydrolysis constants of U⁴⁺ ions. The activation energy is 63±2 kJ mol⁻¹. A reaction mechanism is proposed, in which in the slow stages the complex ion U(OH) ₂ ²⁺ ·CO(NH₂)₂ reacts with TcO²⁺ and TcO²⁺ · CO(NH₂)₂ ions.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 61–66.Original Russian Text Copyright © 2005 by Dvoeglazov, Marchenko, Koltunov.     

Kinetics and Mechanism of Np(IV) Oxidation with Nitric Acid

Neptunium (IV) is oxidized to Np(V) with nitric acid in the presence of U(VI) under conditions of low acidity (<∼0.1 M). The reaction rate is described by the equation d[Np(V)]/dt = k ₁[Np(IV)]/[H⁺]² + k ₂[Np(IV)]²[U(VI)]/[H⁺]³, in which k ₁ = (2.0±0.3) × 10⁻⁵ mol² l⁻² min⁻¹ and k ₂ = (5.50±0.47) × 10⁻² mol l⁻¹ min⁻¹ at 50°C and solution ionic strength μ = 0.5. The activation energies of the two pathways are 148±31 and 122±12 kJ mol⁻¹. The reaction along the main pathway (with the rate constant k ₂) is limited by disproportionation of Np(IV) involving NpOH³⁺ and Np(OH)₂UO ₂ ⁴⁺ complex ions.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 228–233.Original Russian Text Copyright © 2005 by Koltunov, Taylor, Marchenko, Savilova, Dvoeglazov, Zhuravleva.     

Sorption of Iodine,Cesium, and Strontium Radionuclides on Alkaline-Earth Hydroxyphosphates from Aqueous Solutions

Sorption of ¹³¹I⁻, ¹³¹IO ₃ ⁻ , ¹³⁷Cs⁺, ⁸⁵Sr²⁺, and F⁻ ions on synthesized alkaline-earth (AE) (calcium, strontium, and barium) hydroxyphosphates was studied. These hydroxyphosphates were prepared by the reactions MCl₂ +Na₃PO₄ + NaOH = M₅(PO₄)₃OH; MCl₂ + NH₄OH + (NH₄)₂HPO₄ = M₅(PO₄)₃OH; and MCl₂ + NaOH + (NH₄)₂HPO₄ = M₅(PO₄)₃OH (M = Ca, Sr, Ba). All the tested AE hydroxyphosphates do not sorb ionic species of radioactive iodine from aqueous solutions. The highest sorption power with respect to fluoride ion is exhibited by calcium hydroxyphosphate. The degree of ¹³⁷Cs and ⁸⁵Sr sorption recovery from aqueous solutions upon their 120-min contact with AE hydroxyphosphates is ∼5–25 and ∼15–80%, respectively.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 80–84.Original Russian Text Copyright © 2005 by Kulyukhin, Krasavina, Mizina, Rumer, Tanashchuk, Konovalova.     

Crystallization of salts M3[NpO4(OH)2]·nH2O (M = Na, K, Rb, Cs) from concentrated alkali solutions at low temperatures. Synthesis and structure of a new Np(VII) compound, Na3[NpO4(OH)2]·6H2O

Precipitation of salts M₃[NpO₄(OH)₂]·nH₂O (M = Na, K, Rb, Cs) from concentrated alkali solutions at low temperatures (about ?10°C) was studied. From solutions with [OH^?] > 9.5 M, these compounds are isolated as coarse black crystals in high yield without impurity of other phases. The K, Rb, and Cs salts crystallize in the form of the previously studied compounds K₃[NpO₄(OH)₂]·2H₂O and M₃[NpO₄(OH)₂]·3H₂O (M = Rb, Cs). In the case of Na, a new hydrate Na₃[NpO₄(OH)₂]·6H₂O was obtained, and its crystal structure was determined. Crystals of the hexahydrate consist of centrosymmetrical tetragonal-bipyramidal anions [NpO₄(OH)₂]^3?, crystallographically independent Na(1) and Na(2) cations, and water molecules. The coordination surrounding of the Np atom is characterized by noticeable difference (Δ = 0.0203 Å) in the Np-O bond lengths in the equatorial plane of the bipyramid. The [NpO₄(OH)₂]^3? anions are combined with the Na(2) cations to form infinite chains [Na(2)NpO₄(OH)₂(H₂O)₂]^2? in such a manner that the lateral edges of the anion are simultaneously the lateral edges of the Na(2) coordination polyhedron. Incorporation of one of the two crystallographically independent O atoms of the NpO₄ group into the Na(2) coordination surrounding is responsible for a noticeable difference in the Np-O bond lengths in the equator of the [NpO₄(OH)₂]^3? anion. The types of hydrogen bonding in the structures of Na3[NpO₄(OH)₂]·nH₂O (n = 0, 2, 4, 6) are compared.     

Crystal Structure of a Double Oxalate of Np(V) and Co(NH3)

The crystal structure of a dioxalate complex Co(NH₃)₆NpO₂(C₂O₄)₂·1.5H₂O was studied. The structure consists of centrosymmetrical dimeric anions [NpO₂(C₂O₄)₂] ₂ ⁶⁻ , [Co(NH₃)₆]³⁺ cations, and water molecules of crystallization. The NpO ₂ ⁺ dioxocations have close Np-O bond lengths (average 1.824 Å) and are noticeably bent (ONpO angle 175.6°). Each dioxocation in the [NpO₂(C₂O₄)₂] ₂ ⁶⁻ anion is surrounded by five oxygen atoms of three C₂O ₄ ²⁻ anions; the Np coordination polyhedra are pentagonal bipyramids sharing a common edge. __________ Translated from Radiokhimiya, Vol. 47, No. 6, 2005, pp. 495–499. Original Russian Text Copyright ? 2005 by Charushnikova, Krot, Polyakova.     

Synthesis and crystal structure of K3[NpO4(OH)2]

Attempts were made to isolate anhydrous compounds of [NpO₄(OH)₂]^3? anions with heavy alkali metal cations (K, Rb, Cs) by crystallization at elevated temperatures, and the salt K₃[NpO₄(OH)₂] was isolated and studied. Crystals of K₃[NpO₄(OH)₂] consist of tetragonal bipyramidal [NpO₄(OH)₂]^3? anions and K⁺ cations. The [NpO₄(OH)₂]^3? anion occupies the position in the symmetry center. The Np-O distances in this anion are 1.8992(7) and 1.9100(7) Å in the equatorial plane of the bipyramid and 2.3231(8) Å with OH groups. The OH hydrogen atoms participate in weak H bonds [O?O 3.0250(11) Å] linking the anions in layers [NpO₄(OH)₂] _n ^3n? parallel to the (010) plane. In the interlayer space, there are two crystallographically different K atoms. Their coordination number (CN) can be considered to be equal to 7 and 8. Comparison with the structures of the known compounds Na₃[NpO₄(OH)₂] and K₃[NpO₄(OH)₂]·2H₂O was made. The structure of the latter compound was redetermined with higher accuracy. The failure of attempts to prepare the anhydrous rubidium and cesium compounds is probably due to large ionic radius of these cations, requiring high coordination number.     

Redox Reactions of Platinum Elements: XV. Kinetics of Rhodium(III) Oxidation with Xenon Difluoride in Nitric Acid Solutions

The rate of the reaction 2Rh(H₂O)₆ ^{3 +} + XeF₂ = 2Rh(OH)₃ ⁺ + Xe + 2HF + 4H⁺ + 6H₂O is described by the second-order equation -d[Rh(III)]/dt = k ₁[Rh(III)][XeF₂], where k ₁ = 15.4±0.8 l mol^-1 min^-1 at 17.8°C and the solution ionic strength = 2. The activation energy of the reaction is E ₁ = 60.6±1.0 kJ mol^-1. This reaction is complicated by the parallel hydrolysis reaction 2XeF₂ + 2H₂O = 2Xe + O₂ + 4HF. The reaction mechanism includes a slow stage of H atom transfer from Rh(H₂O)₆ ³⁺ to XeF₂ molecule with formation of XeF^. radical as an intermediate. The subsequent stages of Rh(H₂O)₅(OH)³⁺ hydrolysis and reduction of XeF^· radical to Xe proceed rapidly.     

New data on sodium salts of Np(VII) and Pu(VII)

A new Pu(VII) compound, Na₃[PuO₄(OH)₂]·2H₂O, was prepared by X-ray diffraction analysis, and its structure was studied. To reveal the character of actinide contraction in going from Np(VII) to Pu(VII), the geometric parameters of the tetragonal-bipyramidal surrounding of Pu(VII) in the [PuO₄(OH)₂]³⁻ anion were compared with those of Np(VII) in the previously studied isostructural compound Na₃[NpO₄(OH)₂]·2H₂O. To reveal the specific feature of hydrogen bonding in crystals of the general composition Na₃[NpO₄(OH)₂]·nH₂O (n = 0, 2, 4), the structure of the compound Na₃[NpO₄(OH)₂]·4H₂O studied previously by the photographic method was refined. The effect of hydrogen bonds on the geometric characteristics of the coordination polyhedra of the Np and Na atoms was considered.     

Kinetics of Np(VI) Reduction with Butanal Oxime

Reduction of Np(VI) to Np(V) with butanal oxime in the presence of excess reductant is presumably described by the equation 4NpO₂ ²⁺ + 2C₃H₇CHNOH + H₂O = 4NpO₂ ⁺ + 2C₃H₇CHO + N₂O + 4H⁺, and the reaction rate, by the equation -d[Np(VI)]/dt = k[Np(VI)][C₃H₇CHNOH]/[H⁺], with k = 230±15 min^-1 at 25°C and the ionic strength of the solution = 2. This equation holds for solutions with different values of the ionic strength and HNO₃ concentration. The activation energy is 69.4±12.4 kJ mol^-1.     

Complexation and Disproportionation of Np(V) in K10P2W17O61 Solutions

Complexation of NpO₂ ⁺ and NpO₂ ^{2 +} with unsaturated K _n P₂W₁₇O₆₁ ^{n - 1 0} (L ^x-) heteropolyanion and disproportionation of Np(V) in the presence of L ^x- were studied spectrophotometrically. The logarithms (logK) of the formation constants of NpO₂ ^VL and NpO₂ ^{V I}L are 3 and 7, respectively. The K⁺ and Na⁺ cations bind the L ^x- anions, thus decreasing the yield of the complexes. Neptunium(V) disproportionation in K₁₀P₂W₁₇O₆₁ solutions containing 1 M (HClO₄ + NaClO₄) (pH from 0 to 4) and free from NaClO₄ (pH 2-6.5) was studied. The disproportionation rate is described by the equation -d[Np(V)]/dt = k[Np(V)][L ^x-]. The pH dependence of the rate constant passes through a maximum at pH 1. The rate constant decreases with increasing [Na⁺]. The reaction is inhibited by its product, Np(IV). The Np(V) complex is not involved in disproportionation; the reactive species is NpO₂ ⁺ aqua ion, which is probably converted into NpO^{3 +}L ^x-. Then NpO^{3 +}L ^x- rapidly reacts with NpO₂ ⁺, which occurs simultaneously with, or is preceded by release of the second oxygen atom.     

Cation-cation interaction in mixed-valent An(IV)/Np(V) tribromoacetates [An(NpO2)(H2O)3(CBr3COO)5]·CBr3COOH·nH2O,An = Th(IV), Np(IV)

The structure of new mixed-valent An(IV)/Np(V) compounds [An(NpO₂)(H₂O)₃(CBr₃COO)₅]·CBr₃COOH·nH₂O, where An(IV) = Th and Np, was studied. Two independent Np(V) atoms have the coordination surrounding in the form of pentagonal bipyramids with the O atoms of NpO ₂ ⁺ dioxocations in apical positions; the equatorial planes of the bipyramids are constituted by the O atoms of five CBr₃COO^? ions. Two independent An(IV) atoms have the oxygen surrounding in the form of distorted tricapped trigonal prisms (CN = 9) constituted by the O atoms of four CBr₃COO^? ions, two NpO ₂ ⁺ cations, and three water molecules. Eight of ten independent CBr₃COO^? anions link the An⁴⁺ and NpO ₂ ⁺ cations in the bidentate bridging fashion into electrically neutral chains [An(NpO₂)(H₂O)₃(CBr₃COO)₅]n, and two CBr₃COO^? anions interact with two independent NpO ₂ ⁺ dioxocations in the monodentate fashion. CBr₃COOH and water molecules are located between the layers. In the [An(NpO₂)(H₂O)₃(CBr₃COO)₅]n chains, NpO ₂ ⁺ cations alternate with An⁴⁺ cations, and mixed-valent An(IV)/Np(V) cation-cation interaction arises, in which each NpO ₂ ⁺ cation acts as a bidentate ligand and An⁴⁺ acts as coordination center for two dioxocations. [Th(NpO₂)(H₂O)₃(CBr₃COO)₅]·CBr₃COOH·2H₂O is the first example of a Th(IV) compound in which cation-cation bonds with the NpO ₂ ⁺ ions are present.     

Synthesis,Crystal Structure,and Spectral Characteristics of the Np(V) Complex with Triphenylphosphine Oxide [NpO2(PO(C6H5)3)4]ClO4

Single crystals of [NpO₂(PO(C₆H₅)₃)₄]ClO₄ were grown and the structure of this compound was studied (CAD4 diffractometer, MoK ; triclinic unit cell: a = 9.140(2), b = 13.528(3), c = 13.918(3) Å, = 97.14(3)°, = 108.17(3)°, = 91.75(3)°, space group P-1, Z = 1, V = 1618.0 ų, d _{c a l c} = 1.521 g cm^-3; R ₁ = 0.0245 for 5342 observed reflections with F ₀ > 4(F ₀), wR ₂ = 0.0677 for 5601 unique reflections, 419 refined parameters). [NpO₂(PO(C₆H₅)₃)₄]ClO₄ consists of complex cations [NpO₂(PO(C₆H₅)₃)₄]⁺ and disordered ClO_4- anions. The Np(V) atom has tetragonal-bipyramidal oxygen surrounding with coordination number (CN) 6. The NpO₂ group is linear, the O = Np = O bond angle is 180.0°, and the Np = O bond length is 1.797(2) Å. The equatorial coordination plane of the bipyramid is formed by oxygen atoms of four triphenylphosphine oxide (TPPO) molecules. The Np-O_eq bond lengths vary from 2.434(2) to 2.442(2) Å (average 2.438 Å). The O_eq-Np-O_eq bond angle is close to the right angle (88.98°). The average bond lengths in TPPO ligands are P-O 1.498, P-C 1.798, and C-C 1.376 Å; the average bond angles are O-P-O 111.12°, C-P-C 107.78°, P-C-C 120.2, and C-C-C 120.0°. The electronic absorption spectra (Shimadzu UV-3100, 900-1050 nm) and IR spectra (Specord-M80, 400-4000 cm^{- 1}) of crystalline [NpO₂(PO(C₆H₅)₃)₄] were measured in an NaCl matrix. The absence of the main characteristic absorption band of the NpO₂ ⁺ dioxocation (980 nm) in the electronic absorption spectrum suggests centrosymmetrical equatorial surrounding of the Np(V) atom. The narrow absorption band ta_{a s}(NpO₂ ⁺) in the IR spectra in the region of 860 cm^-1 suggests the absence of cation-cation interaction, and its position is consistent with a short Np-O bond length in neptunyl(V) groups.     

Oxidation of Urea with Nitrous Acid in Nitric Acid Solutions

The kinetics of the reaction between urea and HNO₂ in nitric acid solution was studied spectrophotometrically. It was found that, at a constant ionic strength of the solution μ = 2, in the range of the initial concentrations of urea from 0.01 to 0.1 M, HNO₂, from 0.003 to 0.012 M, and hydrogen ions, from 0.1 to 1.5 M, the rate constant of the reaction is described by the equation -d[HNO₂]/dt = k[HNO₂][CO(NH₂)₂][H⁺] · K([H⁺]K +1)⁻¹, where the rate constant k = 15.6±0.3 l mol⁻¹ min⁻¹ and the protonation constant of urea K = 1.38 l mol⁻¹ at 15°C. From the temperature dependence of the reaction rate in the range of 15–35°C, the activation energy was determined to be 61±5 kJ mol⁻¹. The reaction mechanism involving the reaction of nondissociated HNO₂ molecules and protonated urea species NH₂CONH ₃ ⁺ was suggested.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 57–60.Original Russian Text Copyright © 2005 by Dvoeglazov, Marchenko.     

First Observation of the Cation-Cation Interaction of Actinides in Melts: NpO2 +-UO2 2+ System

Study of the absorption spectra of the NpO ₂ ⁺ ion in a CsCl melt containing 2 M UO ₂ ²⁺ , as well as in K₂UO₂Cl₄ and Cs₂UO₂Cl₄ melts (T = 700°C), allowed the first detection of the cation-cation interaction of actinides in melts. In all the molten salts studied, the cation-cation interaction of NpO ₂ ⁺ and UO ₂ ²⁺ is manifested most clearly (via appearance of an additional band) in the ³ H ₅ ³ H ₄ magnetic-dipole transition of the 5f ² configuration of the NpO₂ ⁺ ion (D _4h symmetry) near 1.6 m: Along with a sharp peak of unbound neptunyl(V) at 1660 nm, there is an equally sharp peak at 1633 nm belonging to the cation-cation complex. The intensity ratio for the peaks at 1633 and 1660 nm increases in the series of melts (UO ₂ ²⁺ in CsCl) < K₂UO₂Cl₄ < Cs₂UO₂Cl₄ by two orders of magnitude.     

Synthesis and Structure of the Np(VII) Complex with Guanidinium,Li[C(NH<Subscript>2</Subscript>)<Subscript>3</Subscript>]<Subscript>2</Subscript>[NpO<Subscript>4</Subscript>(OH)<Subscript>2</Subscript>]·6H<Subscript>2</Subscript>O

The previously unknown Np(VII) compound Li[C(NH₂)₃]₂[NpO₄(OH)₂]·6H₂O (I), containing organic cations, was synthesized and studied by single crystal X-ray diffraction. In contrast to the relatively numerous structurally characterized salts of [NpO₄(OH)₂]^3– anions with Na⁺, K⁺, Rb⁺, and Cs⁺ cations, which were prepared only from strongly alkaline media, crystals of I were isolated from solutions with a very low concentration of OH^– ions (about 0.1 M). The compound is relatively stable in storage in the dry form, but is strongly hygroscopic. In the structure of I, there are two independent Np(VII) atoms with the oxygen surrounding in the form of tetragonal bipyramids. In contrast to the other salts of the [NpO₄(OH)₂]^3– anions with singlecharged alkali metal cations, the C(NH₂) ₃ ⁺ ions and hydrated Li⁺ ions in I interact with the oxygen surrounding of Np(VII) only via hydrogen bonds of types O_w–H···O and N–H···O with the formation of a three-dimensional H-bond network.     

Manifestation of Nd ions on the structure,Raman and IR spectra of (TeO<Subscript>2</Subscript>-MoO-Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>) glasses

The structure of [80TeO₂ + (20–x)MoO + xNd₂O₃] glasses, with x = 0, 4, 6, 10 and 12 mol%, is studied in this work. Raman scattering in the spectral range (−2000 to 3500 cm⁻¹) and IR absorption spectra have been measured for crystalline TeO₂ and glasses, and their assignments were discussed and compared. Many vibrational modes were found active in both Raman and IR and their assignments for crystalline TeO₂ and for the glasses were discussed in relation to the tetragonal structure of crystalline α -TeO₂. Nd₂O₃ was found to completely eliminate diffuse scattering and enhance the Raman scattering intensity. Anti-stokes Raman bands in the range −1460 cm^{− 1} to −1975 cm^{− 1} were observed for both (30Li₂O + 70B₂O₃+ xNd₂O₃) glasses and [80TeO₂ + (20−x)MoO + xNd₂O₃] glasses and were attributed to some emission processes due to the doping of the glasses with Nd₂O₃.     

Extraction of Lanthanide(III) Nitrates from Aqueous Solutions with Mixtures n-Octanol-Decane, Tri-n-butyl Phosphate-n-Octanol, and Diisoamyl Methylphosphonate-n-Octanol

Extraction of lanthanide(III) (La-Eu) nitrates from aqueous solutions with 3.15 M solution of octanol (ROH) in n-decane (extractant 1), 2.02 M solution of diisoamyl methylphosphonate (S = DIAMP) in n-octanol (extractant 2), and 1.83 M solution of tri-n-butyl phosphate (S = TBP) in n-octanol (extractant 3) was studied at T = 298.15 K. The extraction of lanthanide(III) nitrates with extractant 1 at C(aq) > 0.6 M is described by the equation of the heterogeneous reaction Ln³⁺(aq) + 3NO ₃ ⁻ (aq) + 4ROH(o) = [Ln(NO₃)₃ ⋅ (ROH)₄](o). The extraction of Ln(III) nitrates with extractants 2 and 3 involves the reaction described above in combination with the heterogeneous reaction Ln³⁺(aq) + 3NO ₃ ⁻ (aq) + 3S(o) = [Ln(NO₃)₃(S)₃](o) and the homogeneous reaction ROH(o) + S(o) = [ROH ⋅ S](o), where S is DIAMP or TBP. The electronic absorption and IR spectra of Nd(III) and Pr(III) nitrates in n-octanol and n-octanol-TBP mixtures were analyzed.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 245–251.Original Russian Text Copyright © 2005 by Kudrova, Keskinov, Pyartman.     

Crystal Structure of Double Co(NH3)6 3 + Np(V) Malonates Co(NH3)6(NpO2C3H2O4)2A·H2O (A = OH and NO3)

X-ray diffraction analysis of Co(NH₃)₆(NpO₂C₃H₂O₄)₂NO₃·H₂O (I) and Co(NH₃)₆(NpO₂· C₃H₂O₄)₂OH·H₂O (II) showed that they consist of [NpO₂C₃H₂O₄] _n ^{n -} infinite anionic chains, [Co(NH₃)₆]^{3 +} cations, NO₃ ^- (I) and OH^- (II) anions, and molecules of crystallization water. The anionic chain structure is similar to that in the known compound Co(NH₃)₆(NpO₂C₃H₂O₄)₂C₃H₃O₄. Neptunium(V) atoms occur in hexagonal-bipyramidal environment. The coordination capacity of malonate anions is 6, and they simultaneously coordinate three neptunyl(V) cations NpO₂ ⁺ in the chain.