[en] A potentiometric study on the complex formation of Cu(II) and UO₂(II) with dimethyl diisoxazolone (RH) in (1:1) water-dioxan at a constant ionix strength (μ=0.5) at 31 +- 0.5deg, has been made. The successive formation constants K₁ and K₂ have been determined following Irving and Rossotti method. Log K₁ and log K₂ are computed by graphical methods and are found to be 1.72, 1.61; 1.61,1.23 for Cu(II) and UO₂(II) respectively. The acid dissociation constant ksup(*) of RH has also been determined in (1:1) water-dioxane as well as in (1:1) water-methanol are found to be pksup(*)=2.88 and 2.40 respectively. (author)

[en] The dimeric bis(imido) uranium complex ({U(NtBu)2(I)(tBu2bpy)}2) (see picture; U green, N blue, I red) has cation-cation interactions between (U(NR)2)+ ions. This f1-f1 system also displays f orbital communication between uranium(V) centers at low temperatures, and can be oxidized to generate uranium(VI) bis(imido) complexes.

[en] Voltammograms of uranocene in benzonitrile under an Ar atmosphere were recorded in studies to measure the controlled oxidation of the compound. The results indicated that cyclooctatetraene (COT) was librated during the electrolysis, and NMR data indicated that no more than ¹/₃ of all the COT ligand was librated as free COT. Combination of these data led to the conclusion that oxidation produced a dimeric or cluster product cation

[en] The [(UO₂)₂F₆-2H₂O]^2- ion has been observed in the Cs₂[(UO₂)2F₆-2H₂O] compound. It is similar to the (UO₂)₂F₈^4- ion already found in the Cs₄(UO₂)₂F₈-2H₂) and Rb₄(UO₂)₂F₈-2H₂O complexes in which two of the fluorine atoms are replaced by two water molecules. Because of the existence of hydrogen bonds, these ions group themselves together in this structure to form chains

[en] The Cp₃UR^- anions 1 react with organic halides R'X (R or R' = Me, nPr, iPr, nBu, allyl, Bz) to give the Cp₃UR and Cp₃UR' compounds. The product distribution indicates that the species Cp₃U(R)(R') should be intermediates in these oxidation reactions. 21 refs

[en] In this work, the PNP ligand ([2-(Ph₂P)C₆H₄]₂N) has been shown to be flexible, hemi-labile, and capable of stabilizing low- and high-valent uranium species. The bis(PNP) framework is then a valuable alternative to the (C₅Me₅) ligand set, offering distinct structures and reaction patterns. (O.M.)

[en] Redox behavior and spectroscopic properties of four heteropoly anions of uranium(IV) have been studied, namely: (a) dodecamolybdouranate(IV), [UMo₁₂O₄₂]^8-, (b) decatungstouranate(IV), [UW₁₀O₃₆]^8-, (c) bis-(undecatungstrophosphato)uranate(IV), [U(PW₁₁O₃₉)₂]^10- and (d) bis-(undecatungstosilicato)-uranate(IV), [U(SiW₁₁O₃₉)₂]^12-. Cyclic voltammetry of the anions in aqueous solutions showed that the complexes [UMo₁₂O₄₂]^8-, [U(PW₁₁O₃₉)₂]^10-, and [U(SiW₁₁O₃₉)₂]^12- were oxidizable to their U(V) analogues. The redox process was found to be pH dependent for [UMo₁₂-O₄₂]^8- and [U(SiW₁₁O₃₉)₂]^12-. The anions [UMo₁₂O₄₂]^8- and [U(PW₁₁O₃₉)₂]^10- can be oxidized electrolytically to stable U(V) isomorphs. The U(V) complexes can be reduced to their corresponding U(IV) species. The anion [U(PW₁₁O₃₉)₂]^10- was isolated as potassium-organic cation double salts which are soluble in a variety of organic solvents. In non-aqueous solutions, [U(PW₁₁O₃₉)₂]^10- can be readily oxidized to the U(V) complex and these solutions of the oxidized anion were found to be indefinitely stable. The electronic absorption spectra of the four heteropoly anions of U(IV) manifested clearly the crystal field effects on the U(IV) chromophore caused by the different site-symmetries provided by the heteropoly ligand. A square-anti-prismatic coordination of U(IV) in [U(PW₁₁O₃₉)₂]^10- and [U-(SiW₁₁O₃₉)₂]^12- was inferred from electronic absorption spectra. In non-aqueous media, the spectrum of [U(PW₁₁O₃₉)₂]^9- was characterized by a narrow absorption band at 6.51 kK which was assigned to the pure electronic transition of the U(V) chromophore

[en] A multisyringe flow injection analysis method for the determination of uranium in water samples was developed. The methodology was based on the complexation reaction of uranium with arsenazo (III) at pH 2.0. Uranium concentrations were spectrophotometrically detected at 649 nm using a light emitting diode. Under the optimized conditions, a linear dynamic range from 0.1 to 4.0 μg mL^-1, a 3σ detection limit of 0.04 μg mL^-1, and a 10σ quantification limit of 0.10 μg mL^-1 were obtained. The reproducibility (%) at 0.5, 2.5, and 4.0 μg mL^-1 was 2.5, 0.9, and 0.6%, respectively (n = 10). The interference effect of some ions was tested. The proposed method was successfully applied to the determination of uranium in water samples. (author)

[en] In clean, one-pot procedures, the uranium complex reductively cleaves azides and azo compounds to generate bis(imido) derivatives. This unusual reaction has not been observed previously in either the actinide series or with a metallocene complex. (orig.)

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