- Lewis Acidic Behavior of MoOF4 towards the Alkali Metal Fluorides in Anhydrous Hydrogen Fluoride Solutions
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Previous studies performed on samples of MoOF4 dissolved in anhydrous hydrogen fluoride (aHF) solutions have indicated the presence of the [Mo2O2F9]– anion. Building upon this earlier work, MoOF4, and MF (M = Li–Cs) were dissolved in aHF solutions to produce M[Mo2O2F9] (M = Li–Cs) salts. Structural analysis of the obtained compounds was performed using single-crystal X-ray diffraction. This study provides the first single crystal structures for the [MoVI 2O2F9]– anion. Additionally, IR and Raman spectroscopy were used to characterize each salt. These spectra were compared to calculated ones for the solid-state structure of each salt using the DFT-PBE0 density functional method. The calculated spectra were used to give band assignments in the experimentally obtained spectra.
- Stene, Riane E.,Scheibe, Benjamin,Karttunen, Antti J.,Petry, Winfried,Kraus, Florian
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- Reductive photo-chemical separation of the hexafluorides of uranium and molybdenum
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Two new techniques are described for the separation of molybdenum hexafluoride (MoF6) from uranium hexafluoride (UF6). Both separation techniques utilize the differences displayed by the hexafluorides in their ability to absorb light in the near UV region. Because UF6 absorbs light in the near UV region and MoF6 does not, this observation was used to selectively reduce UF6 to uranium pentafluoride (UF5) through irradiation with 395 nm light in the presence of a suitable reducing agent. Two reducing agents were chosen for this study: gaseous, liquid, or super-critical carbon monoxide (CO) and liquid sulfur dioxide (SO2). Since MoF6 is not reduced under the reaction conditions described here, it may be removed via distillation from the uranium-containing sample after complete reduction of UF6 to solid UF5. The molybdenum- and uranium-containing samples were measured for purity through elemental analysis using microwave plasma atomic emission spectroscopy (MP-AES). Elemental analysis showed more than 98.8 % of the Mo had been removed from the U-containing samples. Further analyses of the samples were performed by X-ray powder diffraction and IR spectroscopy.
- Chemnitz, Tobias,Kraus, Florian,Petry, Winfried,Stene, Riane E.
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supporting information
(2020/10/18)
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- The Molybdenum(V) and Tungsten(VI) Oxoazides [MoO(N3)3], [MoO(N3)3·2 CH3CN], [(bipy)MoO(N3)3], [MoO(N3)5]2-, [WO(N3)4], and [WO(N3)4·CH3CN]
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A series of novel molybdenum(V) and tungsten(VI) oxoazides was prepared starting from [MOF4] (M=Mo, W) and Me3SiN3. While [WO(N3)4] was formed through fluoride-azide exchange in the reaction of Me3SiN3 with WOF4 in SO2 solution, the reaction with MoOF4 resulted in a reduction of MoVI to MoV and formation of [MoO(N3)3]. Carried out in acetonitrile solution, these reactions resulted in the isolation of the corresponding adducts [MoO(N3)3·2 CH3CN] and [WO(N3)4·CH3CN]. Subsequent reactions of [MoO(N3)3] with 2,2′-bipyridine and [PPh4][N3] resulted in the formation and isolation of [(bipy)MoO(N3)3] and [PPh4]2[MoO(N3)5], respectively. Most molybdenum(V) and tungsten(VI) oxoazides were fully characterized by their vibrational spectra, impact, friction and thermal sensitivity data and, in the case of [WO(N3)4·CH3CN], [(bipy)MoO(N3)3], and [PPh4]2[MoO(N3)5], by their X-ray crystal structures.
- Haiges, Ralf,Skotnitzki, Juri,Fang, Zongtang,Dixon, David A.,Christe, Karl O.
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supporting information
p. 15550 - 15555
(2016/01/26)
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- Separation of metallic residues from the dissolution of a high-burnup BWR fuel using nitrogen trifluoride
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Nitrogen trifluoride (NF3) was used to fluorinate the metallic residue from the dissolution of a high burnup, boiling water reactor fuel (~70 MWd/kgU). The washed residue included the noble-metal phase (containing ruthenium, rhodium, palladium, technetium, and molybdenum), smaller amounts of zirconium, selenium, tellurium, and silver, along with trace quantities of plutonium, uranium, cesium, cobalt, europium, and americium, likely as their oxides. Exposing the noble metal phase to 10% NF3 in argon, between 400 and 550 °C, removed molybdenum and technetium near 400 °C as their volatile fluorides, and ruthenium near 500 °C as its volatile fluoride. The events were thermally and temporally distinct and the conditions specified provide a recipe to separate these transition metals from each other and from the nonvolatile residue. Depletion of the volatile fluorides resulted in substantial exothermicity. Thermal excursion behavior was recorded with the thermal gravimetric instrument operated in a non-adiabatic, isothermal mode; conditions that typically minimize heat release. Physical characterization of the noble-metal phase and its thermal behavior are consistent with high kinetic velocity reactions encouraged by the nanoparticulate phase or perhaps catalytic influences of the mixed platinum metals with nearly pure phase structure. Post-fluorination, only two products were present in the residual nonvolatile fraction. These were identified as a nano-crystalline, metallic palladium cubic phase and a hexagonal rhodium trifluoride (RhF3) phase. The two phases were distinct as the sub-μm crystallites of metallic palladium were in contrast to the RhF3 phase, which grew from the parent, nano-crystalline noble-metal phase during fluorination, to acicular crystals exceeding 20-μm in length.
- McNamara, Bruce K.,Buck, Edgar C.,Soderquist, Chuck Z.,Smith, Frances N.,Mausolf, Edward J.,Scheele, Randall D.
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supporting information
p. 1 - 8
(2014/05/06)
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- Chemical interaction of fluoropolymers with transition metals
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Chemical interaction of transition metals (Mo, W, Ta, Nb, and Ti) with a tetrafluoroethylene-vinylidene fluoride (TFE-VDF) copolymer (21 mol % TFE + 79 mol % VDF) has been studied by differential scanning calorimetry (DSC) and mass spectrometry. The DSC c
- Tarasov,Alikhanian,Arkhangel'Skii
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p. 809 - 813
(2009/12/01)
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- Infrared spectra of the products of interaction of tungsten and Molybdenum with fluorine isolated in solid argon
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The IR spectra of the products formed when molecular fluorine passed over molybdenum and tungsten (heated to 100-1100°C) and isolated in inert matrices at 12 K were recorded. In the W + F2 system, the major product was tungsten hexafluoride. For the Mo + F2 system, bands of MoF6, MoOF4, (MoF5)3, MoF5, MoF4, and, possibly, MoF3 were identified. The spectra were interpreted with the use of thermodynamic calculations of the equilibrium composition of the gas phase at various temperatures. The structure of metal fluorides of different compositions is discussed.
- Osin,Davlyatshin,Ogden
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p. 237 - 245
(2007/10/03)
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- Controlled hydrolysis of the hexafluorides of molybdenum, tungsten, and rhenium: Structure of oxonium (μ-fluoro)bis(tetrafluorooxotungstate(VI))
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The controlled hydrolysis reactions of the hexafluorides of molybdenum, tungsten, and rhenium in anhydrous hydrogen fluoride are reported. Vibrational spectra indicate that the hydrolysis of MoF6 yields solely MoOF4, as previously believed. Hydrolysis of ReF6 yields a mixture of ReOF4 and H3O+Re2O2F9-, while WF6 hydrolyzes to give only H3O+W2O2F9-, even with excess WF6. These reactions suggest that WOF4 is a stronger Lewis acid than MoOF4. H3O+W2O2F9- crystallizes in the monoclinc space group P2/n (a nonstandard setting of P2/c, No. 13). At 293 K, a = 14.818 (3) ?, b = 5.198 (1) ?, c = 5.576 (1) ?, β = 94.41 (1)°, V = 428.2 ?3, and Z = 2. Refinement converged with R = 0.090, and Rw = 0.098 for 784 independent observed X-ray diffraction reflections. The structure consists of discrete ions with a fluorine-bridged W2O2F9- anion. The angle at the bridge is 144 (2)° with the bridging W-F distance being 2.13 (1) ?. The average terminal W-F distance is 1.86 (2) ?, and W=O, being trans to the bridge, is 1.57 (3) ?. The fluorine and oxygen atoms are approximately hexagonally close packed.
- Hoskins, Bernard F.,Linden, Anthony,O'Donnell, Thomas A.
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p. 2223 - 2228
(2008/10/08)
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