[en] Elemental iodine is oxidized by molybdenum or uranium hexafluoride in acetonitrile at ambient temperature to give bis(acetonitrile) iodine(I) hexafluoromolybdate(V) or hexafluorouranate(V). The solids' vibrational spectra are consistent with linear co-ordination of MeCN to I⁺. Co-ordinated MeCN is readily displaced by pyridine (py) to give an [I(py)₂]⁺ salt. In MeCN solution the solvated I⁺ decomposes to give I₂ as one product, it iodinates benzene and its derivatives, and oxidizes the solvated copper(I) cation, NO, and thallium metal to give the solvated copper(II) cation, NO⁺, and a mixture of solvated cations of Tlsup(I) and Tlsup(III) respectively. The solvated thallium(III) cation oxidizes iodine ion in MeCN at room temperature giving I₂ or solvated I⁺ depending on the concentration ratio. Oxidation states of solvated thallium cations are conveniently identified by ²⁰⁵Tl n.m.r. spectroscopy. (author)

[en] The adsorption equilibrium of uranium from aqueous solutions containing tricarbonatouranate (V1) ions on a polymer bearing amidoxime groups was examined at pH 8-9. It is suggested that the adsorption proceeds by ligand exchange of three carbonate ions on the central uranyl (V1) ion with two amidoxime groups, accompanied by deprotonations. The uranyl (V1) complex formed with the polymer was found to be more stable than that with acetamidoxime as a ligand, suggesting that the amidoxime polymer has potential for the recovery of uranium from sea-water. (author)

[en] The single-crystal EPR spectra of γ-irradiated pure K₂[MoO(O₂)F₄]·H₂O and molybdenum-doped K₂[Nb(O₂)F₅]·H₂O, each giving rise to a set of resonances both at low and high fields relative to that of the free-electron g value, have been investigated. The high-field lines are similar for both complexes and are attributed to an electron-excess species [MoOF₄]^-, formed from [MoO(O₂)F₄]^2- by radiation damage followed by rearrangement due to the extra electron. The low-field lines of the Mo-doped niobium compound are due to a niobium hole species [Nb(O₂)F₅]^-, having the unpaired electron occupying the non-bonding orbital of the peroxo oxygen atoms. However, the low-field lines of the pure molybdenum complex are due to a hole species, [Mo(O₂)F₄]⁺. Further support for the assumed species comes from extended Huckel molecular orbital calculations. The crystal structure of the pure molybdenum complex was redetermined. (author)

[en] Six co-ordinate complexes of technetium(v) and rhenium(v) containing the M0³⁺ core with tri- and bi-dentate Schiff-base ligands were synthesized and characterized. The complexes with general formula [M0(L¹)L] [M = Tc or Re; L¹ = N-(2-oxidophenyl)salicylideneiminate; L = salicylideneiminate, N-methyl- and N-phenyl-salicylideneiminate, or 8-quinolinolate (quin)] were characterized by elemental analysis, i.r., ¹H n.m.r., and mass spectroscopy. The structure of [Tc0(L¹) (quin)] was also determined by X-ray analysis. The co-ordination around the metal is approximately octahedral. The phenolic oxygen of the quin ligand is trans to the Tc=0 group. The tridentate Schiff-base ligand lies on the equatorial plane with respect to Tc=0. The complex crystallizes in monoclinic space group P2₁/n with a = 15.496(8), b = 10.355(4), c 12.122(5) A, β 109.03(6)⁰, and Z = 4. The structure has been refined to R = 0.054 for 2 025 observed reflections. (author)

[en] The potentiometric titration technique has been used to study molybdenum (VI) equilibria in 1.0 mol dm^-3 sodium nitrate and at 25 ⁰C. Numerical treatment of the data indicates that the 'best' model includes the species [HMoO₄]^-, H₂MoO₄, [Mo₇O₂₄]^6-, [Mo₇O₂₃(OH)]^5-, [Mo₇O₂₂(OH)₂]^4-[Mo₇O₂₁(OH)₃]^3-, [Mo₈O₂₆]^4-, and [Mo₁₀O₃₄]^8-whose formation constants, log βsub(pq), are, respectively, 3.92, 8.09, 52.49, 57.57, 61.33, 64.96, 73.18, and 79.15. Evidence is given for the existence of a high-molecular-weight species even though computational limitations preclude its identification. A 'slow' region of equilibrium has also been found and its kinetics studied. The reaction mechanism is discussed; the rate constants of the forward and backward reaction, k₁ and ksub(-1), are 642 + - 300 dm⁶ mol-?² s^-1 and (2.51 + - 1.00) x 10^-5 s^-1, respectively. Further evidence for the co-ordination numbers of the protonated forms of the molybdate ion is given. (author)

[en] The substitution reaction of [1-B₁₀H₉(N₂)]^- with N,N-dimethylthioformamide and the acid-catalyzed nucleophilic substitution of [B₁₀H₁₀]^2- with tetramethylthiourea gave [1-B₁₀H₉(SCH=NMe₂)]^- and [2-B₁₀H₉braceSC(NMe₂)₂brace]^-, respectively. The basic hydrolysis of these thioamide complexes yielded the 1- and 2-isomers of [B₁₀H₉(SH)]^2-respectively. Their stereochemistry was determined by ¹H n.m.r. spectroscopy from the S-Me chemical shift values of their S-methyl derivatives. (author)

[en] Infrared spectra of uranyl(VI) species adsorbed from aqeuous [UO₂(CO₃)₃]^4- solutions on to a polymer having amidoxime groups were examined in order to obtain information on the adsorption mechanism. The subtraction spectra in a region of 500-1 500 cm^-1 exhibit only a distinct band at 886 cm^-1 ascribed to the v₃ mode of the O=U=O moiety and no band assigned to carbonato ligands, suggesting the existence of a carbonato-free uranyl(VI) complex; this is consistent with the adsorption equilibrium reported previously. (author)

[en] The evolution in air of four different neodymia samples, two of them with hexagonal structure and the other two cubic, has been studied. Upon exposure to air the four samples become heavily hydrated. Likewise, carbonation, though much less intense, does affect the bulk oxides. The behaviour of the hexagonal samples on the one hand, and that of the cubic oxides on the other, was found to be quite different. Dissimilarities were observed in the rates of the aging processes, being much faster for the cubic oxides, in the nature of the carbonated phases, and in the thermal evolution of samples stabilized in air. In the case of the cubic neodymium oxides, a crystalline carbonate hydroxide-like phase, isostructural with that observed for cubic samaria and europia samples aged in air, was found. By contrast, the carbonated phase of the hexagonal neodymias seems to be similar to those detected for hexagonal lanthana, as well as for a monoclinic sample of samaria. The results, in addition to showing that the behaviour in air of the rare-earth-metal oxides is much more complex than presumed earlier, give further support to the tentative classification of these oxides into three groups. (author)

[en] The reaction of oxalic acid (H₂ox) with [AsPh₄][TcNCl₄] and [NBu₄][TcOCl₄] in aqueous acetone yields crystals of [AsPh₄]₄[Tc₄N₄O₂(ox)₆] (1) and, after precipitation with AsPh₄Cl, [AsPh₄]₂[TcO(ox)₂(Hox)]·3H₂O (2) respectively. Complex (1) crystallises in the monoclinic space group P2₁/n with cell parameters a = 14.433(1), b 13.229(1), c = 27.020(1) A, β 92.90(1)⁰, and Z = 4. Refinement with data measured with Cu-Ksub(α) radiation converged at R = 0.069 for 3 076 observed reflections. The anion in (1) is a cyclic tetranuclear complex, [Tc₄N₄O₂(ox)₆]^4-, with Csub(i) point symmetry. Each technetium (VI) atom is co-ordinated by five oxygen atoms and one nitrogen atom to give a distorted octahedron. In each half of the anion, a quadridentate oxalato ligand forms a bridge between the two octahedra, each of which is also linked to an adjacent octahedron by the corner sharing of an oxo ligand. Two oxygen atoms of a bidentate oxalato ligand and a nitrido nitrogen complete the octahedral co-ordination in each polyhedron. The Tc....Tc spacings of 3.586(2) and 5.756(3) A preclude any Tc-Tc bonding. The monoclinic crystals of complex (2) belong to the space group P2₁/c with a 16.495(3), b = 14.802(2), c = 21.805(4) A, β = 98.76(1)⁰, and Z = 4. Refinement with 5 099 observed data measured with Mo-Ksub(α) radiation converged at R = 0.059. The technetium(V) atom is co-ordinated by six oxygen atoms to give a distorted octahedron. The structure of the anion is unusual in that it contains a protonated unidentate oxalato ligand and that there is no appreciable lengthening of the Tc-O bond trans to the oxo ligand. (author)

[en] When thorium or uranium tetrachlorides are isolated in neon matrices, the spectra can be interpreted in terms of a T_d molecule with a small site effect. Spectra obtained using sputtering techniques to generate ThCl₄ in argon matrices agreed with those obtained previously using conventional vaporisation techniques. Detailed calculations of the i.r. spectra of isotopically enriched and natural abundance Th^35/37Cl₄ show that in krypton ThCl₄ is not tetrahedral. (author)