Journal of Inorganic and Nuclear Chemistry最新文献

The extraction of Eu(III) and Am(III) from lithium nitrate solution by several neutral phosphorus-based extractants has been studied as a function of temperature in the range of 0–50°C. From the variation of the distribution ratio with temperature the thermodynamic quantities ΔG, ΔH and ΔS have been calculated for these extractions. The results of this study indicate that these two metal ions behave quite similarly in respect to the basicity and the steric bulk of the extractant molecules. Extraction of these metals is enhanced significantly with increasing basicity of the extractant but is inhibited with increasing steric bulk of the phosphorus compounds.

The thermodynamics of the $\text{NO}{}_3{}^{\mathrm{-}}\text{Cl}{}^{\mathrm{-}}\text{,}\text{NO}{}_3{}^{\mathrm{-}}\text{Br}{}^{\mathrm{-}}$ and $\text{NO}{}_3{}^{\mathrm{-}}\text{SCN}{}^{\mathrm{-}}$ exchanges in hydrous ceria was studied. The $\text{NO}{}_3{}^{\mathrm{-}}\text{Cl}{}^{\mathrm{-}}$ and $\text{NO}{}_3{}^{\mathrm{-}}\text{SCN}{}^{\mathrm{-}}$ exchanges in this exchanger are enthalpy directed while the $\text{NO}{}_3{}^{\mathrm{-}}\text{Br}{}^{\mathrm{-}}$ exchange is entropy directed. Consideration of these results and other results on hydrous zirconia shows that although selectivity reversals of the “normal” selectivity sequence of monovalent anions do occur in the weak-base hydrous oxides, these reversals may be due to changes in the oxide entropy, which are ignored in the Eisenman model. Noncoulombic electrostatic interactions, which are also ignored in the model, are probably dominant in certain cases and seem to contribute considerably to the enthalpy and solid entropy changes. The Eisenman model seems to throw some light on the phenomena involved in anion exchanges on hydrous oxides.

A systematic study of the preparation of synthetic pollucite (CsAlSi₂O₆) by high temperature solid state reaction was performed. Eighteen different combinations of cesium oxide, alumina and silica sources and three firing temperatures were evaluated. The most effective methods of preparing phase-pure pollucite were identified and the chemical compositions of large batches of pollucite prepared by three of these methods were obtained. Reference X-ray powder diffraction data were obtained for the most nearly stoichiometric synthetic pollucite specimen.

The synthesis and crystal structure of the title compound are described. The complex crystallizes in the trigonal system, space group P31c with a = 16.053(12), $\text{c = 6.839(8)}\text{A}\text{̊}$ and Z = 2. The structure was solved by the heavy-atom method from 1252 counter reflections, and refined by least-squares methods to R 0.054. Six carboxylate oxygen atoms belonging to the three nearly planar p-amino-salicylate ions fill the equatorial region of the linear uranyl ion, giving the U atom an hexagonal-bipyramidal coordination overall. The hexagon is slightly puckered (± 0.05 Å), bond lengths and angles are as expected [U-O(apical) 1.78(e), U-O(eq) 2.47(2) Å]. The exact water content (and thereafter the Na⁺ coordination) is not entirely certain, but seems to approximate to 6H₂O. The intramolecular hydrogen bond between the phenolic and a carboxylate oxygen atom, present in the free acid, is not destroyed by coordination.

Values for the thermodynamic functions (enthalpy and entropy changes) were determined for the formation of mixed complexes of transition metals with uramildiacetic acid (UDA) and nitrilotriacetic acid (NTA) as “primary” ligand and glycine as secondary ligand, using the temperature coefficient method.

The mixed complexes are stabilized by the enthalpy changes in the reaction of MX with L; entropy changes are unfavourable to complex formation. There results were interpreted in terms of the covalent and electrostatic contributions of the metal-nitrogen and metal-carboxylate interactions as well as of structural modifications in the complexes to the overall enthalpy changes.

The results obtained were complemented by a spectrophotometric study of the complexes formed by cobalt, copper and nickel.

The ¹³C and ¹⁹F NMR of nine metal complexes contained perfluoroethylmonothio-β-diketonate ligands are recorded in chloroform-d. The complexes are of the type M[RC(S)CHC(O)C₂F₅]_n where M is of nickel, palladium or cobalt; n is 2 or 3 and R is 2′-thienyl, phenyl or 2′-naphthyl. The ¹³C-NMR data support a fac-octahedral geometry for the cobalt complex (n=3). The ¹⁹F NMR show the chemical shift of the difluoromethylene group to be metal dependent. Correlations between the chemical shifts of the respective carbon resonances are also presented and NMR data for the three corresponding β-diketones, RC(OH) = CHC(O)C₂F₅, are described.

A molybdenum anode can be oxidised electrochemically into acetonitrile/X₂ media (X = Cl, Br, I), with current efficiencies which are lower than for the analogous chromium system. The subsequent work-up of solutions prepared by this method yields products containing molybdenum in either + II or + V oxidation states. A tentative reaction scheme is presented. Tungsten could not be oxidised electrochemically under the conditions used.