Potentiometric studies of the complexes of chromium(VI), molybdenum(VI) and tungsten(VI) with some Azoxine S dyes

The equilibrium constants of the complexation reactions of Cr(VI), Mo(VI) and W(VI) with 8-hydroxyquinoline-5-sulphonic acid (OXS), 7-phenylazo-8-hydroxyquinoline-5-sulphonic acid (PAZOXS), 7-(4-sulphophenylazo)-8-hydroxyquinoline-5-sulphonic acid (SPAZOXS) and 7-(4-sulphonaphthylazo)-8-hydroxyquinoline-5-sulphonic acid (SNAZOXS) have been determined by potentiometric pH titration. The values in the case of chromate are different from those for molybdate and tungstate. The order of stabilities is OXS > PAZOXS > SPAZOXS > SNAZOXS.     

Oxo/sulfidotungstate(VI) as precursors to W(VI)O2, W(VI)OS, and W(VI)S2 complexes and W(IV)-dithiolene chelate rings

Synthetic models leading to oxosulfidotungsten(VI) groups and dithiolene chelate rings have been investigated. The heterogeneous reaction systems [WO4-nSn]2-/2Ph3SiCl/Me4phen (n = 0-2) in acetonitrile afford the complexes [WQ2(OSiPh3)2(Me4phen)] (1-3) in the indicated yields containing the groups W(VI)O2 (1; 86%), W(VI)O2 (2; 45%), and W(VI)S2 (3; 83%). In the crystalline state these complexes have imposed C2 symmetry, with cis-oxo/sulfido and trans-silyloxide ligands. 1H NMR spectra indicate that this stereochemistry is retained in solution. The colors of 2 (yellow, 367 nm) and 3 (orange, 451 nm) arise from LMCT absorptions at the indicated wavelengths. These results demonstrate that the silylation procedure previously introduced for the preparation of molecules with the Mo(VI)OS group (Thapper, et al. Inorg. Chem. 1999, 38, 4104) extends to tungsten. Methods for the formation of dithiolene chelate rings MS2C2R2 in reactions with sulfide-bound M = Mo or W precursors are summarized. In a known reaction type, 3 and activated acetylenes rapidly form [W(IV)(OSiPh3)2(Me4phen)(S2C2R2)] (R = CO2Me, 4, 83%, and Ph, 5, 98%). In a new reaction type not requiring the isolation of an intermediate, the systems [MO2S2]2-/2Ph3SiCl/Me4phen/PhC=CPh in acetonitrile afford 5 (68%) and [Mo(IV)(OSiPh3)2(Me4phen)(S2C2Ph2)] (6; 61%). Complexes 5 and 6 are isostructural, maintain the trans-silyloxide stereochemistry, and exhibit chelate ring dimensions indicative of ene- 1,2-dithiolate coordination. Reductions in the -1.4 to -1.7 V range are described as metal-centered. It remains to be seen whether the oxo/sulfidotungsten(VI) groups in 1-3 eventuate in the active sites of tungstoenzymes. (Me4phen = 3,4,7,8-tetramethyl-1,10-phenanthroline.)     

Uran(VI) und Plutonium(VI)

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EFFECT OF SUBSTITUTION POSITION OF HYDROXY GROUP AT BENZOIC ACID ON THE LUMINESCENT AND DEGRADATION PROPERTIES OF POLY[DI（CARBOXYPHENYL） SUCCINATE-co-SEBACIC ANHYDRIDE]S

In this work, two new diacids, di（m-carboxyphenyl） succinate （m-dCPS） and di（o-carboxyphenyl） succinate （o- dCPS）, were synthesized by reaction of m-, o-hydroxy benzoic acid with succinic chloride, respectively. Their corresponding copolymers with sebacic acid （SA）, P（m-dCPS：SA） and P（o-dCPS：SA）, were prepared by melt copolycondensation and characterized by NMR, UV and DSC methods. Compared with inherently fluorescent poly[di（p-carboxyphenyl） succinate- co-sebacic anhydride] （P（p-dCPS：SA））, P（m-dCPS：SA） and P（o-dCPS：SA） displayed different luminescent properties. P（m- dCPS：SA） could emit fluorescence under the excitation of both visible and UV light, while P（o-dCPS：SA） could only emit fluorescence when excited with UV light. Degradation rate of the two new copolyanhydrides increased with the increase of SA fraction in the copolymers. In addition, P（o-dCPS：SA） degraded more rapidly than P（m-dCPS：SA） with the same composition. Typical surface-degradation characteristics of these copolyanhydrides were observed.     

Ab initioMO calculations for the oxides,oxyacids, and oxyanions of S(IV) and S(VI)

Ab initio molecular orbital (MO ) calculations for two series of sulfur–oxygen compounds are reported: the S(IV ) system of SO₂, H₂SO₃, HSO, and SO, and the S(VI ) system of SO₃, H₂SO₄, HSO, and SO. Geometries about the sulfur atoms were optimized using the STO -3G* basis set; energies at these geometries were computed by the STO ?3G and 44-31G basis sets both with and without five Gaussian d orbitals on S. The sulfur–oxygen bond lengths and the angles about the central atoms agree fairly well with experiment. The stabilization energy associated with the addition of the d orbitals was found to be a constant amount per bond (ca. 54 and 28 kcal mole^?1 in the minimal and extended bases, respectively) in hypervalent compounds. The isomer HSO was predicted to be more stable than SO₂(OH)^?, but the reverse was true for HSO₂(OH) compared to SO(OH)₂. The deprotonation energies for the acids and the hydration energies for the oxides also were computed and discussed with reference to experimental data.     

Sulphate and fluoride complexing of U(VI), Np(VI) and Pu(VI)

The complex formation of U(VI), Np(VI) and Pu(VI) with sulphate and fluoride ions was studied in HClO₄H₂SO₄ and HClO₄HF solutions respectively at an ionic strength of 2·0 and [H⁺] = 2·0 M by the distribution method employing the liquid cation exchanger dinonyl naphthalene sulphonic acid as the extractant. An attempt was made to explain the order of the stability constant values obtained.     

Aminobis(phenolate)s of imidomolybdenum(VI) and -tungsten(VI)

The reactions of trans-[MoO(ONO^Me)Cl₂] 1 (ONO^Me = methylamino-N,N-bis(2-methylene-4,6-dimethylphenolate) dianion) and trans-[MoO(ONO^tBu)Cl₂] 2 (ONO^tBu = methylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenolate) dianion) with PhNCO afforded new imido molybdenum complexes trans-[Mo(NPh)(ONO^Me)Cl₂] 3 and trans-[Mo(NPh)(ONO^tBu)Cl₂] 4, respectively. As analogous oxotungsten starting materials did not show similar reactivity, corresponding imido tungsten complexes were prepared by the reaction between [W(NPh)Cl₄] with aminobis(phenol)s. These reactions yielded cis- and trans-isomers of dichloro complexes [W(NPh)(ONO^Me)Cl₂] 5 and [W(NPh)(ONO^tBu)Cl₂] 6, respectively. The molecular structures of 4, cis-6 and trans-6 were verified by X-ray crystallography. Organosubstituted imido tungsten(VI) complex cis-[W(NPh)(ONO^tBu)Me₂] 7 was prepared by the transmetallation reaction of 6 (either cis or trans isomer) with methyl magnesium iodide.     

Anderson-type heteropolyanions of molybdenum(VI) and tungsten(VI)

The previously reported preparation of some Anderson-type molybdopolyanions containing divalent metal ions (Zn, Cu, Co or Mn) as a heteroatom has been reinvestigated. The molybdopolyanions of Zn(II) and Cu(II) were confirmed, although the Cu(II) polyanion was not stable and could not be recrystallized. On the other hand, the polyanions of Co(II) and Mn(II) could not be reproduced. Another type of heteropoly compound, [X(H₂O)_6-x(Mo₇O₂₄)]⁴⁻ [X = Cu(II), Co(II) or Mn(II)], was isolated as solids, which are not stable thermally. The mixed-type Anderson polyanions, [Ni(II)Mo_6-xW_x,O₂₄H₆]⁴⁻, which have been questioned as mixtures of species with different x values, were also reinvestigated using IR, UV absorption and MCD spectra. They are single species, but not mixtures, although some positional isomers may be present for the compounds where x = 2-4. The possibility of oxidation of the heteroatom with the Anderson structure maintained was examined. The oxidation of [Ni(II)Mo₆O₂₄H₆]⁴⁻ by the S₂O²⁻₈ ion in aqueous solution gave the Waugh-type [Ni(IV)Mo₉O₃₂]⁶⁻ polyanion, whereas the oxidation of [Ni(II)W₆O₂₄H₆]⁴⁻ gave no heteropoly compound.     

Uran(VI)

Ohne Zusammenfassung     

Uran (VI)

Ohne Zusammenfassung     

Nitrosyl-pentafluorotellurat(VI)

Nitrosyl pentafluorotellurate(VI) . NO+OTeF₅^? is prepared from NOCl and Hg(OTeF₅)₂. It is ionic NO+OTeF₅^? in the solid state and in acetonitrile solution, in the gaseous state however a covalent molecule ON–OTeF₅.     

Wolfram(VI)-fluorid-pentafluorotellurate(VI): WFn(OTeF5)6-n

Tungsten(VI) Fluoride Pentafluorotellurates(VI): WF_n(OTeF₅)_6-n In WF₆ fluorine can be replaced by F₅TeO groups by means of B(OTeF₅)₃ to form WF_n(OTeF₅)_6-n. Isolation was achieved for WF₅OTeF₅ and cis-WF₄ (OTeF₅)₂. Compounds with n > 2 have been identified by ¹⁹F-nmr spectroscopy. The ligand behaviour of the F₅TeO group is compared to OMe and OPh.     

Syntheses,Characterization and Stereochemistry of S - and R,S -Hydrogenmalato Dioxotungsten(VI)

Cis -dioxo hydrogenmalato tungstates(VI) j -Na 2 [WO 2 ( S -Hmal) 2 ]·4H 2 O 1 , and Na 2 [WO 2 ( R , S -Hmal) 2 ] 2 (H 3 mal = malic acid) have been prepared from the reactions of excess S- malic acid and R , S -malic acid respectively, with sodium tungstate at ambient temperature. Both complexes were characterized by elemental analyses, conductivity measurement, optical rotation, UV-Vis, IR and NMR spectroscopy. Complex 1 was obtained with predetermined helical chirality at the metal center for a j - cis -configuration, which is established by single crystal X-ray diffraction. The crystal is orthorhombic, space group P 2 1 2 1 2 1 , with unit cell parameters: a = 7.9545(6), b = 10.7440(8), c = 21.045(2)Å, V = 1798.6(2)Å 3 , Z = 4, D c = 2.215 g cm m 3 , F (000) = 1152, R = 0.031, R w = 0.034. Single crystal X-ray diffraction reveals that the cis- dioxo tungstate 1 is octahedrally coordinated by the S -malate through the deprotonated f -hydroxy and f -carboxylate groups, while the g -carboxylic acid groups remain uncomplexed.     

Syntheses and vibrational spectra of xenon(VI) fluorogallate,xenon(VI) fluoroaluminate and xenon(VI) fluoroindate

Liquid xenon difluoride at 140°C does not react with aluminium, gallium, and indium trifluorides, neither does liquid xenon hexafluoride at 60°C. Therefore the reactions between the corresponding hydrazinium fluorometalates (N₂H₆AlF₅, N₂H₆GaF₅ and N₂H₅InF₄) and XeF₂ and XeF₆ were carried out. N₂H₆AlF₅, N₂H₆GaF₅ and N₂H₅InF₄ react with XeF₂ at 60°C (at 25°C in the case of indium) yielding only the corresponding trifluorides, while the reaction with XeF₆ proceeds at room temperature (at - 25°C in the case of indium) yielding XeF₆.2AlF₃, XeF₆.GaF₃ and xenon(VI) fluoroindate(III) contaminated with indium trifluoride. Spectroscopic evidence suggests that these compounds are salts of the XeF⁺₅ cation squashed between polymeric anions of the type (M₂F₇)^x-_x or (MF₄)^x-_x.     

Vibrational spectra of hepta- and octafluorocomplexes of molybdenum(VI), tungsten(VI) and rhenium(VI)

The alkali salts of the seven- and eight-coordinated fluoro-complexes of Mo, W and Re have been prepared. Their vibrational spectra were recorded. The spectra of all ElF^n-₈ are consistent with a square antiprismatic arrangement of the fluorine ligands. The spectra of Cs ElF₇ (El = Mo, W, Re) and Rb ReF₇ are similar to those known for ReF₇ and JF₇ and can be interpreted on the basis of pentagonal bipyramid (D_5h). If Cs⁺ is replaced by lighter alkali ions in Me ElF₇ (El = Mo and W), a lowering of symmetry is apparent from the number of bands observed in the vibrational spectra.     

Kinetic-spectrophotometric determination of molybdenum (VI) and tungsten (VI) in mixtures

A simple kinetic-spectrophotometric method is described for the determination of molybdenum(VI) and tungsten(VI) in mixtures, without prior separation. The method is based on the catalytic effect of molybdenum(VI) and tungsten(VI) on the oxidation of 2,4-diaminophenol dihydrochloride (DAP) by hydrogen peroxide in acidic medium. The reaction was followed spectrophotometrically by measuring the rate of change in absorbance with time at 500 nm. A partial inhibition in the catalytic activity of each catalyst, when the other one is present, at all ratios of Mo(VI) W(VI) mixtures studied was observed. On the other hand, the catalytic activity of tungsten(VI) dropped to zero whilst that of molybdenum(VI) decreased slightly, in the presence of citrate ions. Two sets of experiments were carried out, the first in the absence and the other in the presence of citrate, and the resolution of Mo(VI)/W(VI) mixtures was achieved by solving two simultaneous equations. Various molar ratios of Mo(VI) W(VI), at the 10^–6 M level, from 0.2 1 to 5 1 can be determined with satisfactory precision and accuracy. The selectivity of the method was investigated and the method was applied successfully to the determination of molybdenum and tungsten in each other's presence in steel.     

Das Ionenaustauschverhalten von Wolfram (VI) und Molybd?n (VI)

Ohne Zusammenfassung