[en] The complexes of Np(IV) and U(IV) with unsaturated heteropolyanion SiW₁₁O₃₉^8- have been prepared in single crystal form, their structures have been determined by X-ray structural analysis. Actinide atoms in [An(SiW₁₁O₃₉)₂]^12- complex anions are eight-coordinated. Their coordination polyhedra can be described as distorted square anti-prisms. The main distortion of the coordination polyhedron in both complexes is twisting of one base of the square anti-prism from its ideal position by about 9 angle around the fourfold inversion axis. (authors)

[en] The synthesis, crystal and molecular structure of the first representatives of polynuclear technetium clusters are described. The composition of these clusters is: [Tc₈Br₄μ-Br₈]Br · 2 H₂O; [H(H₂O)₂][Tc₈Br₄μ-Br₈]Br; [H(H₂O)₂]₂[Tc₈Br₄μ-Br₈]Br₂; [H₃O(H₂O)₃]₂[Tc₆Br₆μ₃-Br₅]; [(C₄H₉)₄N]₂[Tc₆Br₆μ₃-Br₅]; [H₃O(H₂O)₃]₂[Tc₆Br₆μ₃-Br₅] · 4 H₂O. It is shown that these clusters strongly differ in their structure from the known clusters of other d-elements. The crystal and molecular structure of hexabromotechnetium acid (H₃O)₂TcBr₆ is studied too. (author)

[en] The tendency of Pu(IV) to hydrolyze and form true solutions, colloid solutions, or insoluble precipitates has been known since the Manhattan Project. Since then, specific studies have been performed to examine in detail the equilibria of Pu(IV) hydrolytic reactions in various media. Great attention also has been paid to the preparation, structure, and properties of Pu(IV) polymers or colloids. These compounds found an important application in sol-gel technology for the preparation of nuclear fuel materials. A most important result of these works was the conclusion that Pu(IV) hydroxide, after some aging, consists of very small PuO₂ crystallites and should therefore be considered to be Pu(IV) hydrous oxide. However, studies of the properties and behavior of solid Pu(IV) hydroxide in complex heterogeneous systems are rare. The primary goal of this investigation was to obtain data on the composition and properties of Pu(IV) hydrous oxide or other compounds formed in alkaline media under different conditions. Such information is important to understand Pu(IV) behavior and the forms of its existence in the Hanford Site alkaline tank waste sludge. This knowledge then may be applied in assessing plutonium criticality hazards in the storage, retrieval, and treatment of Hanford Site tank wastes as well as in understanding its contribution to the transuranic waste inventory (threshold at 100 nCi/g or about 5 x 10^-6 M) of the separate solution and solid phases

No abstract available

[en] (NpO₂)₂SiO₄.2H₂O (I) and (PuO₂)₂SiO₄.2H₂O (II) have been prepared by hydrothermal synthesis technique. Chemical composition of (I) was attributed to the compound from its isostructurality with (UO₂)₂SiO₄.2H₂O; crystal unit cell parameters of (NpO₂)₂SiO₄.2H₂O have been refined as orthorhombic, a = 8.365(5) A, b = 11.089(5) A, c = 18.640(9) A with the space group Fddd. (PuO₂)₂SiO₄.2H₂O has not been found isostructural with uranyl(VI) and neptunyl(VI) analogues. Chemical composition of (II) was determined by chemical analysis and proved by the formula volume calculated from powder X-ray data. Indexing of X-ray powder pattern of the prepared compound gave the tetragonal unit cell with a = 6.912(3), c = 18.563(3) A, possible space group I4₁/amd. Visible-near IR and IR absorption spectra of the prepared compounds have been measured in NaCl and KBr. f-f absorption band of PuO₂²⁺ in the visible spectrum of crystal (PuO₂)₂SiO₄.2H₂O is not splitted but its maximum is essentially shifted (up to 858 nm) to the long wave region in comparison with hydrated PuO₂²⁺ ions. Visible-near IR absorption spectrum of crystal (NpO₂)₂SiO₄.2H₂O is close to that of aqueous neptunyl(VI) solution. Thermal behavior of synthesized compounds has been studied up to 800 C in air. (orig.)

[en] Single crystals of [AnO₂(bipy)(OOCC₆H₄NO₂)-(H₂O)].0.5bipy (An=Np, Pu, bipy=2,2^'-bipyridine) have been synthesized and their structures have been determined by X-ray analysis. The compounds are isomorphous and contain electroneutral complexes [AnO₂(bipy)(OOCC₆H₄NO₂)(H₂O)] and solvate bipy molecules. Actinide atoms in both compounds are seven coordinated. Actinide contraction results in a shortening of all bonds in the coordination spheres at the transition from Np to Pu. The structures are compared with those of other An(V) benzoate compounds. In contrast to earlier structurally characterized An(V) benzoates, cation-cation interaction in [AnO₂(bipy)(OOCC₆H₄NO₂)(H₂O)] complexes is absent. Lower complexing ability of m-nitrobenzoate is compensated by engagement of water molecule into the coordination sphere of An(V). This is accompanied by formation of strong H-bonds between AnO₂⁺ cations and coordinated water molecules. (orig.)

[en] This work presents our latest results on the coordination polyhedron of the tetranitrate lanthanide complexes with aza and carboxy ligands. Structures in the solid state have been determined by X-ray single crystal diffraction and solution studies have been carried out by X-ray Absorption Spectroscopy at the cation L_III edge. Comparison is made with the Am cation. (authors)

No abstract available

[en] Full text of publication follows: Carbonic acids are essential components of numerous natural liquids. Therefore, the study of their interaction with actinides is an important issue for general understanding of migration processes of transuranium elements in the environment. Here we present the results of our recent work on complexing reactions between AnO₂ⁿ⁺ (An Np, Pu; n = 1, 2) and anions of malonic acid (CH₂(COO)₂^2- L_mlnt^2-) and ortho-phthalic acid (C₆H₄(COO)₂^2- = L_phthl^2-). Np(VI) and Pu(VI) reduction by these organics has also been in the focus of the study. Based on the obtained data on the stability of solutions and on complex formation data in neutral media, the conditions of solid phase isolation have been determined. The crystal compound PuO₂L_mlnt.3H₂O was prepared and found to be isostructural to the known UO₂L_mlnt.3H₂O. It was impossible to isolate the NpO₂²⁺ analogue due to its rapid reduction to pentavalent state by malonate ions. Under the same conditions, the PuO₂²⁺ reduction rate was found to be several times lower. Novel plutonium(V) compounds MPuO₂L_mlnt.nH₂O (M = Na, NH₄ and Cs) have been synthesized. It has been shown that the mono-phthalate complex compounds of Np(VI) and Pu(VI) can be isolated - AnO₂L_phthl.2H₂O and AnO₂L_phthl.1.33H₂O (the latter from hot solution). Neptunium and plutonium di-hydrates have different structures: NpO₂L_phthl.2H₂O crystallizes in triclinic and PuO₂L_phthl.2H₂O in monoclinic modification. The AnO₂L_phthl.1.33H₂O compounds were found to be isostructural. Hydrogen peroxide addition to a neutral plutonyl(VI) phthalate solution stabilizes plutonium in pentavalent oxidation state. Plutonium(V) bi-phthalate complex can be precipitated as [Co(NH₃)₆][PuO₂L_phthl2].2H₂O isostructural with its Np analogue. All novel crystalline solids have been characterized by XRD, TG/DTA methods, IR and UV-Vis absorption spectroscopy. (authors)

[en] The results of X-ray structural investigations are presented for several Tc coordination compounds investigated recently: [Tc₂(μ-CH₃COO)₄][TcO₄]₂, [Fe(C₅H₅)₂][TcO₄], [Fe(C₅H₅)₂]₄-(H₁₁O₅)₂[TcCl₆]₃, [Fe(C₅H₅)₂]₃[Tc₆I₁₄], [Tc(CO)₃Cl]₄ and [Tc(CO)₃Br^.uen]. The electronic structure and bonding (from EHT calculations) of [Tc₂(μ-CH₃COO)₄][TcO₄]₂, [Tc(CO)₃Cl]₄, [Tc(CO)₃Br^.uen] and of some hypothetical Tc compounds with similar structures are also discussed. (orig.)