- Comments on reactions of oxide derivatives of uranium with hexachloropropene to give UCl4
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We report that U3O8, UO2(NO3)2·6H2O, and UO2Cl2 react with hexachloropropene (HCP) to give UCl4 in 60, 100, and 92% yields, respectively, and report a protocol to recycle the HCP. This renders the preparation of UCl4 more accessible and sustainable. 2,5-Dichlorohexachlorofulvene has been identified as a significant by-product from these reactions.
- Patel, Dipti,Wooles, Ashley J.,Hashem, Emtithal,Omorodion, Harrison,Baker, Robert J.,Liddle, Stephen T.
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- The Exceptional Diversity of Homoleptic Uranium–Methyl Complexes
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Homoleptic σ-bonded uranium–alkyl complexes have been a synthetic target since the Manhattan Project. The current study describes the synthesis and characterization of several unprecedented uranium–methyl complexes. Amongst these complexes, the first example of a homoleptic uranium–alkyl dimer, [Li(THF)4]2[U2(CH3)10], as well as a seven-coordinate uranium–methyl monomer, {Li(OEt2)Li(OEt2)2UMe7Li}n were both crystallographically identified. The diversity of complexes reported herein provides critical insight into the structural diversity, electronic structure and bonding in uranium–alkyl chemistry.
- Autschbach, Jochen,Baker, Tessa M.,Brennessel, William W.,Neidig, Michael L.,Sears, Jeffrey D.,Sergentu, Dumitru-Claudiu
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- Synthesis and structure of (Ph4P)2MCl6 (M = Ti, Zr, Hf, Th, U, Np, Pu)
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High-purity syntheses are reported for a series of first, second, and third row transition metal and actinide hexahalide compounds with equivalent, noncoordinating countercations: (Ph4P)2TiF6 (1) and (Ph4P)2MCl6 (M = Ti, Zr, Hf, Th, U, Np, Pu; 2-8). While a reaction between MCl4 (M = Zr, Hf, U) and 2 equiv of Ph4PCl provided 3, 4, and 6, syntheses for 1, 2, 5, 7, and 8 required multistep procedures. For example, a cation exchange reaction with Ph4PCl and (NH4)2TiF6 produced 1, which was used in a subsequent anion exchange reaction with Me3SiCl to synthesize 2. For 5, 7, and 8, synthetic routes starting with aqueous actinide precursors were developed that circumvented any need for anhydrous Th, Np, or Pu starting materials. The solid-state geometries, bond distances and angles for isolated ThCl62-, NpCl6 2-, and PuCl62- anions with noncoordinating counter cations were determined for the first time in the X-ray crystal structures of 5, 7, and 8. Solution phase and solid-state diffuse reflectance spectra were also used to characterize 7 and 8. Transition metal MCl 62- anions showed the anticipated increase in M-Cl bond distances when changing from M = Ti to Zr, and then a decrease from Zr to Hf. The M-Cl bond distances also decreased from M = Th to U, Np, and Pu. Ionic radii can be used to predict average M-Cl bond distances with reasonable accuracy, which supports a principally ionic model of bonding for each of the (Ph 4P)2MCl6 complexes.
- Minasian, Stefan G.,Boland, Kevin S.,Feller, Russell K.,Gaunt, Andrew J.,Kozimor, Stosh A.,May, Iain,Reilly, Sean D.,Scott, Brian L.,Shuh, David K.
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- Isolation of the large {actinide}38 poly-oxo cluster with uranium
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By controlling the water content, a new poly-oxo-metalate species containing 38 uranium centers has been solvothermally synthesized in the presence of benzoic acid in tetrahydrofuran (THF). The {U38} motif contains a distorted UO2 core of fluorite type, stabilized by benzoate and THF molecules. This compound is analogous to the {Pu38} motif and was characterized by X-ray photoelectron spectroscopy and magnetic analyses.
- Falaise, Clément,Volkringer, Christophe,Vigier, Jean-Fran?ois,Beaurain, Arnaud,Roussel, Pascal,Rabu, Pierre,Loiseau, Thierry
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- Coffinite, USiO4, Is Abundant in Nature: So Why Is It so Difficult to Synthesize?
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Coffinite, USiO4, is the second most abundant U4+ mineral on Earth, and its formation by the alteration of the UO2 in spent nuclear fuel in a geologic repository may control the release of radionuclides to the environment. Despite its abundance in nature, the synthesis and characterization of coffinite have eluded researchers for decades. On the basis of the recent synthesis of USiO4, we can now define the experimental conditions under which coffinite is most efficiently formed. Optimal formation conditions are defined for four parameters: pH, T, heating time, and U/Si molar ratio. The adjustment of pH between 10 and 12 leads probably to the formation of a uranium(IV) hydroxo-silicate complex that acts as a precursor of uranium(IV) silicate colloids and then of coffinite. Moreover, in this pH range, the largest yield of coffinite formation (as compared with those of the two competing byproduct phases, nanometer-scale UO2 and amorphous SiO2) is obtained for 250°C, 7 days, and 100% excess silica. (Figure Presented).
- Mesbah, Adel,Szenknect, Stephanie,Clavier, Nicolas,Lozano-Rodriguez, Janeth,Poinssot, Christophe,Den Auwer, Christophe,Ewing, Rodney C.,Dacheux, Nicolas
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- Facile syntheses of pure uranium halides: UCl4, UBr4 and UI4
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Herein we describe convenient lab scale syntheses of several uranium(iv) halides of high purity by reaction of AlX3 (X = Cl, Br and I) with UO2, which is readily available by reduction of uranyl salts like UO2(NO3/su
- Rudel, Stefan S.,Kraus, Florian
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- Convenient synthesis, structure, and reactivity of (C5Me5)U(CH2C6H5)3 : A simple strategy for the preparation of monopentamethylcyclopentadienyl uranium(IV) complexes
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A high-yield one-pot synthesis of (C5Me5)U(CH2C6H5)3 has been developed and applied to the synthesis of a new organouranium complex possessing a (pentamethylcyclopentadienyl)bis(cyclopentadienyl) ligand framework, (C5Me5)(C5H5)2U(CH2 C6H5). Both complexes have been structurally characterized. We also report herein an improved and safer synthesis for the popular uranium starting material UCU.
- Kiplinger, Jaqueline L.,Morris, David E.,Scott, Brian L.,Burns, Carol J.
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- Crystal structures of 2,2′:6′,2″-terpyridine uranyl chlorides molecular assemblies and their luminescence signatures
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A series of three compounds bearing uranyl cations and 2,2′:6′, 2″-terpyridine (terpy) has been hydrothermally synthesized from uranium tetrachloride aqueous solution. An oxidation process into the hexavalent state has been observed for uranium in these synthesis conditions, together with the crystallization of different phases, which have been characterized by single-crystal X-ray diffraction analysis. The tetrachloridodioxidouranate terpyridinium salts UO2Cl4·H 2terpy·H2O (1) and UO2Cl 4·(H2terpy)2·2Cl (2) consist of the molecular assemblies of tetrachloro-uranyl anions ([UO2Cl 4]2-, square plane bipyramidal environment), isolated to each other via the doubly protonated H2terpy molecules. The latter chelate either water (1) or chlorine anions (2). The addition of organic base such as pyridine favored the crystallization of the complex, UO 2Cl2(terpy) (3), with the neutral terpy moiety coordinating one uranyl center via the nitrogen atoms of the pyridyl rings. It resulted in one uranyl center bonded to three nitrogen and two terminal chlorine anions, located in a distorted equatorial plane and two terminal perpendicular uranyl oxygens in apical position of a pentagonal bipyramid ([UO 2Cl2N3]). Different π-π interactions between the pyridyl rings of neighboring terpy molecules also occur for these complexes. Fluorescence spectroscopy of these different complexes has been measured at room temperature and 77 K showing the various local environments of the emitting centers.
- Lhoste, Jér?me,Henry, Natacha,Loiseau, Thierry,Guyot, Yannick,Abraham, Francis
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- [UCl4(HCN)4]-a hydrogen cyanide complex of uranium tetrachloride
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The reaction of uranium tetrachloride with anhydrous liquid hydrogen cyanide yields a turquoise microcrystalline powder of tetrachloridotetraformonitrileuranium(iv), [UCl4(HCN)4]. We determined the crystal structure of this compound by powder neutron diffraction. The compound was further characterized by IR spectroscopy and thermogravimetric analysis as well as by magnetic measurements. The paramagnetic compound crystallizes in the tetragonal space group type I4. To the best of our knowledge this compound represents the first structurally elucidated uranium(iv) complex with HCN as a ligand.
- Rudel,Pietzonka,Hoelzel,Kraus
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- Synthesis, structure, and characterization of uranium(IV) phenyl phosphonate, U(O3PC6H5)2, and uranium(IV) pyro phosphate, UP2O7
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Two tetravalent uranium compounds have been characterized. The structure of a new uranium(IV) phosphonate, U(O3PC6H5)2, has been solved from laboratory X-ray powder diffraction data by using ab initio methodology. U(O3PC6H5)2 crystallizes in the space group C2/m with a = 9.4559(7) A, b = 5.6769(5) A, c = 14.9687(12) A, β= 96.539(5) A, V = 798.3(1) A3, Z = 2. The reliability factors were RWP = 8.0%, RP = 6.04%, and RF = 3.0%. The structure is lamellar, and the framework of the U(O3P)2 layers is similar to that of the α-Zr(HPO4)2·H2O-type structure, although the symmetry of the phosphonate group is higher than that of the phosphate groups in α-Zr(HPO4)2·H2O and the phosphonate group in Zr(O3PC6H5)2. The phenyl groups are located in the interlamellar space, being inclined 10° to the c-axis. The phenyl rings are tilted out 53° from the ac plane, and they are disordered. We have also characterized this compound by UV-VIS-IR spectroscopies and thermal analysis. The thermal decomposition product is uranium(IV) pyro phosphate. This compound was identified through its X-ray powder diffraction pattern. UP2O7 crystallizes in the Pa3 space group (a = 8.6311(2) A, V = 642.99(4) A3, Z = 4). The structure belongs to the cubic ZrP2O7-type structure. The reliability factors were RWP = 11.7%, RP = 8.6%, and RF = 10.4%. Disorder has been found in the oxygen that bridges the pyrophosphate groups, leading to an angular P-O-P arrangement. The VIS-near-IR adsorption spectra revealed the uranium(IV) presence and the oxygen environment.
- Cabeza, Aurelio,Aranda, Miguel A. G.,Cantero, Fernando M.,Lozano, Diego,Martinez-Lara, Maria,Bruque, Sebastian
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- How to explain the difficulties in the coffinite synthesis from the study of uranothorite?
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The preparation of Th1-xUxSiO4 uranothorite solid solutions was successfully undertaken under hydrothermal conditions (T = 250 °C). From XRD and EDS characterization, the formation of a complete solid solution between x = 0 (thorite) and x = 0.8 was evidenced. Nevertheless, additional (Th,U)O2 dioxide and amorphous silica were systematically observed for the highest uranium mole loadings. The influence of kinetics parameters was then studied to avoid the formation of such side products. The variation of the synthesis duration allowed us to point out the initial formation of oxide phases then their evolution to a silicate phase through a dissolution/precipitation process close to that already described as coffinitization. Also, the uranium mole loading initially considered was found to significantly influence the kinetics of reaction, as this latter strongly slows down for x > 0.3. Under these conditions, the difficulties frequently reported in the literature for the synthesis of pure USiO4 coffinite were assigned to a kinetic hindering associated with the coffinitization reaction.
- Costin,Mesbah,Clavier,Dacheux,Poinssot,Szenknect,Ravaux
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- Near-infraredC-term MCD spectroscopy of octahedral uranium(v) complexes
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C-term magnetic circular dichroism (MCD) spectroscopy is a powerful method for probing d-d and f-f transitions in paramagnetic metal complexes. However, this technique remains underdeveloped both experimentally and theoretically for studies of U(v) complexes ofOhsymmetry, which have been of longstanding interest for probing electronic structure, bonding, and covalency in 5f systems. In this study,C-term NIR MCD of the Laporte forbidden f-f transitions of [UCl6]?and [UF6]?are reported, demonstrating the significant fine structure resolution possible with this technique including for the low energy Γ7→ Γ8transitions in [UF6]?. The experimental NIR MCD studies were further extended to [U(OC6F5)6]?, [U(CH2SiMe3)6]?, and [U(NC(tBu)(Ph))6]?to evaluate the effects of ligand-type on the f-f MCD fine structure features. Theoretical calculations were conducted to determine the Laporte forbidden f-f transitions and their MCD intensity experimentally observed in the NIR spectra of the U(v) hexahalide complexes,viathe inclusion of vibronic coupling, to better understand the underlying spectral fine structure features for these complexes. These spectra and simulations provide an important platform for the application of MCD spectroscopy to this widely studied class of U(v) complexes and identify areas for continued theoretical development.
- Autschbach, Jochen,Cary, Samantha K.,Curran, Daniel J.,Ganguly, Gaurab,Heit, Yonaton N.,Kozimor, Stosh A.,L?ble, Matthias W.,Minasian, Stefan G.,Neidig, Michael L.,Wolford, Nikki J.
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- Homoleptic Aryl Complexes of Uranium (IV)
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The synthesis and characterization of sterically unencumbered homoleptic organouranium aryl complexes containing U?C σ-bonds has been of interest to the chemical community for over 70 years. Reported herein are the first structurally characterized, steric
- Wolford, Nikki J.,Sergentu, Dumitru-Claudiu,Brennessel, William W.,Autschbach, Jochen,Neidig, Michael L.
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- Solution and Solid State Structural Chemistry of Th(IV) and U(IV) 4-Hydroxybenzoates
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Organic ligands with carboxylate functionalities have been shown to affect the solubility, speciation, and overall chemical behavior of tetravalent metal ions. While many reports have focused on actinide complexation by relatively simple monocarboxylates such as amino acids, in this work we examined Th(IV) and U(IV) complexation by 4-hydroxybenzoic acid in water with the aim of understanding the impact that the organic backbone has on the solution and solid state structural chemistry of thorium(IV) and uranium(IV) complexes. Two compounds of the general formula [An6O4(OH)4(H2O)6(4-HB)12]·nH2O [An = Th (Th-1) and U (U-1); 4-HB = 4-hydroxybenzoate] were synthesized via room-temperature reactions of AnCl4 and 4-hydroxybenzoic acid in water. Solid state structures were determined by single-crystal X-ray diffraction, and the compounds were further characterized by Raman, infrared, and optical spectroscopies and thermogravimetry. The magnetism of U-1 was also examined. The structures of the Th and U compounds are isomorphous and are built from ligand-decorated oxo/hydroxo-bridged hexanuclear units. The relationship between the building units observed in the solid state structure of U-1 and those that exist in solution prior to crystallization as well as upon dissolution of U-1 in nonaqueous solvents was investigated using small-angle X-ray scattering, ultraviolet-visible optical spectroscopy, and dynamic light scattering. The evolution of U solution speciation as a function of reaction time and temperature was examined. Such effects as well as the impact of the ligand on the formation and evolution of hexanuclear U(IV) clusters to UO2 nanoparticles compared to prior reported monocarboxylate ligand systems are discussed. Unlike prior reported syntheses of Th and U(IV) hexamers where the pH was adjusted to ~2 and 3, respectively, to drive hydrolysis, hexamer formation with the HB ligand appears to be promoted only by the ligand.
- Vanagas, Nicole A.,Wacker, Jennifer N.,Rom, Christopher L.,Glass, Elliot N.,Colliard, Ian,Qiao, Yusen,Bertke, Jeffery A.,Van Keuren, Edward,Schelter, Eric J.,Nyman, May,Knope, Karah E.
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- Formation of a sol of mixed U(IV) ? U(VI) hydroxide in aqueous solutions with pH 1.5-4
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Addition of a Cs2UCI6 sample to solutions with pH 1.5 - 4, saturated with argon and containing 1 × 10-4-0.1 MUO 2(CIO4)2' results in the appearance of U(V), so that U(IV), U(V), and U(VI) occur in an equilibrium. However, after a certain induction period, black colloidal particles containing U(IV) polymer start to form. With an increase in pH from 1.5 to 4 or in temperature, the induction period becomes shorter. Under anaerobic conditions, the colloidal solution is stable for more than a month. Centrifugation at 8000 rpm (5500g) allows separation of the colloidal particles from the liquid phase. The colloid slowly dissolves in mineral acids saturated with argon or in a K2CO 3 solution, whereas precipitates of individual freshly prepared U(IV) and U(VI) hydroxides dissolve rapidly. Short UV irradia-of a UO 2(ClO4)2 solution saturated with argon and containing ethanol (pH 2.5) results in the appearance of U(V) which then disproportionates, and U(IV) forms with U(VI) a black colloid similar to that arising on mixing U(IV) and U(VI) solutions.
- Gogolev,Shilov,Peretrukhin,Yusov,Fedoseev
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- Synthesis and characterization of uranium (IV) phosphate-hydrogenphosphate hydrate and cerium (IV) phosphate-hydrogenphosphate hydrate
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A new uranium (IV) phosphate of proposed formula U2(PO 4)2HPO4·H2O, i.e. uranium phosphate-hydrogenphosphate hydrate (UPHPH), was synthesized in autoclave and/or in polytetrafluoroethylene closed containers at 150 °C by three ways: from uranium (IV) hydrochloric solution and phosphoric acid, from uranium dioxide and phosphoric acid and by transformation of the uranium hydrogenphosphate hydrate U(HPO4)2·nH2O. The new product appears similar to the previously published thorium phosphate-hydrogenphosphate hydrate Th2(PO4)2HPO4·H2O (TPHPH). From preliminary studies, it was found that UPHPH crystallizes in monoclinic system (a=2.1148(7)nm, b=0.6611(2)nm, c=0.6990(3)nm, β=91.67(3)° and V=0.9768(10)nm3). Heated under inert atmosphere, this compound is decomposed above 400 °C into uranium phosphate-triphosphate U2(PO4)P3O10, uranium diphosphate α-UP2O7 and diuranium oxide phosphate U 2O(PO4)2. Crystallized cerium (IV) phosphate-hydrogenphosphate hydrate Ce2(PO4) 2HPO4·H2O (CePHPH) was also synthesized from (NH4)2Ce(NO3)6 and phosphoric acid solutions by the same method (monoclinic system: a=2.1045(5)nm, b=0.6561(2)nm, c=0.6949(2)nm, β=91.98(1)° and V=0.9588(9)nm3). When heating above 600 °C, cerium (IV) is reduced into Ce (III) and forms a mixture of CePO4 (monazite structure) and CeP3O 9.
- Brandel,Clavier,Dacheux
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- Spectroscopic speciation and structural characterisation of uranyl(VI) interaction with pyridine carboxylic acid N-oxide derivatives
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Spectroscopic speciation of U(VI) solutions holding pyridine carboxylic acid N-oxides in a range pH 2.3-4.5 results in the single component spectrum of the U(VI) isonicotinic acid N-oxide complex. The molar absorption is 14 ± 2 L mol-1 cm-1 at 415.4 nm. The formation constant lg KUL = 2.1 ± 0.2 (k = 2) is derived from solution modelling and by multivariate chemometric analysis. The first crystal structure analysis of a U(VI) pyridine carboxylic acid N-oxide revealed a sheet-like structure where the isonicotinic acid N-oxide binds to the uranyl(VI) both bidentately by the carboxylate group and monodentately by the N-O group. The single component spectrum of the [UO2L]+ (where L- is isonicotinate N-oxide) is compared to the small number of other U(VI) single ligand species. The comparison revealed the possible pitfalls of U(VI) spectroscopic speciation close to the pH region where U(VI) hydrolysis starts to interfere. On basis of the results for U(VI)-L coordination and physicochemical properties of the pyridine carboxylic acid N-oxides some conclusions could be drawn on the likely behaviour of nicotinic acid N-oxide and picolinic acid N-oxide. For the former, complex formation in a narrow range of pH and U(VI) concentrations close to the hydrolysis range of U(VI) might reveal thermodynamic data. In the case of picolinic acid N-oxide, additional experimental evidence is required to characterize suitable conditions.
- Lis, Stefan,Meinrath, Guenther,Glatty, Zbigniew,Kubicki, MacIej
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- Syntheses, structures, and magnetic and optical properties of the compounds [Hg3Te2][UCl6] and [Hg4As2][UCl6]
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Two new quaternary salts, [Hg3Te2][UCl6] and [Hg4As2][UCl6], have been synthesized and their structures determined by single-crystal X-ray diffraction analysis. [Hg3Te2][UCl6] is the product of a reaction involving UCl4, HgCl2, and HgTe at 873 K. The compound crystallizes in space group P21/c of the monoclinic system. [Hg4As2][UCl6] results from the reaction of U, Hg2Cl2, and As at 788 K. It crystallizes in space group Pbca of the orthorhombic system. [Hg3Te2][UCl6] has a two-dimensional framework of ∞2 [Hg3 Te22 +] layers, whereas [Hg4As2][UCl6] has a three-dimensional framework of ∞2 [Hg3 As2] layers interconnected by Hg atoms linearly bonded to As atoms. Both framework structures contain discrete [UCl6]2- anions between the layers. [Hg3Te2][UCl6] exhibits temperature-independent paramagnetism. The optical absorption spectra of these compounds display f-f transitions.
- Bugaris, Daniel E.,Ibers, James A.
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- Facile Syntheses of pure Uranium(III) Halides: UF3, UCl3, UBr3, and UI3
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Herein we describe a convenient lab scale synthesis for pure and solvent-free binary uranium(III) halides UCl3, UBr3, and UI3. This is achieved by the reduction of the respective uranium(IV) halides with elemental silicon in borosilicate ampoules at moderate temperature. The silicon tetrahalides SiX4 formed as a side product are utilized for the removal of excess starting material via a chemical vapor transport reaction. The syntheses introduced herein avoid the need for pure metallic uranium and are based on uranium(IV) halides synthesized from UO2 and the respective aluminum halides and purified by chemical vapor transport. These uranium(III) halides are obtained in single crystalline form. A similar reaction yields UF3 as a microcrystalline powder. However, no beneficial transport reaction occurs with this halide. Also, a higher temperature has to be applied and steel ampoules have to be used. The identities and purity of the products were checked by powder X-ray diffraction as well as IR spectroscopy. The synthesis of UI3 enabled its crystal structure determination on single crystals for the first time. UI3 crystallizes in the PuBr3 structure type with space group type Cmcm and a = 4.3208(9), b = 13.923(3), c = 9.923(2) ?, V = 596.9(2) ?3, and Z = 4 at T = 100 K.
- Rudel, Stefan S.,Deubner, H. Lars,Scheibe, Benjamin,Conrad, Matthias,Kraus, Florian
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- Three-dimensional MOF-type architectures with tetravalent uranium hexanuclear motifs (U6O8)
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Four metal-organic frameworks (MOF) with tetravalent uranium have been solvothermally synthesized by treating UCl4 with rigid dicarboxylate linkers in N,N-dimethylfomamide (DMF). The use of the ditopic ligands 4,4′-biphenyldicarboxylate (1), 2,6-naphthalenedicarboxylate (2), terephthalate (3), and fumarate (4) resulted in the formation of three-dimensional networks based on the hexanuclear uranium-centered motif [U6O4(OH)4(H2O)6]. This motif corresponds to an octahedral configuration of uranium nodes and is also known for thorium in crystalline solids. The atomic arrangement of this specific building unit with organic linkers is similar to that found in the zirconium-based porous compounds of the UiO-66/67 series. The structure of [U6O4(OH)4(H2O)6(L) 6]·X (L=dicarboxylate ligand; X=DMF) shows the inorganic hexamers connected in a face-centered cubic manner through the ditopic linkers to build up a three-dimensional framework that delimits octahedral (from 5.4A for 4 up to 14.0A for 1) and tetrahedral cavities. The four compounds have been characterized by using single-crystal X-ray diffraction analysis (or powder diffraction analysis for 4). The tetravalent state of uranium has been examined by using XPS and solid-state UV/Vis analyses. The measurement of the Brunauer-Emmett-Teller surface area indicated very low values (Langmuir 2 g-1 for 1, 2 g-1 for 2-4) and showed that the structures are quite unstable upon removal of the encapsulated DMF solvent. Copyright
- Falaise, Clement,Volkringer, Christophe,Vigier, Jean-Francois,Henry, Natacha,Beaurain, Arnaud,Loiseau, Thierry
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- Stabilization of Tetravalent 4f (Ce), 5d (Hf), or 5f (Th, U) Clusters by the [α-SiW9O34]10- Polyoxometalate
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The reaction of Na10[α-SiW9O34] with tetravalent metallic cations such as 4f ((NH4)2Ce(NO3)6), 5d (HfCl4), or 5f (UCl4 and Th(NO3)4) i
- Duval, Sylvain,Béghin, Sébastien,Falaise, Clément,Trivelli, Xavier,Rabu, Pierre,Loiseau, Thierry
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- Electrochemical behaviour of uranium (IV) in DMF at vitreous carbon
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The electrochemical behaviour of UCl4 (0.01 mol L-1 up to 0.05 mol L-1) in 0.1 mol L-1 TBAPF6/DMF solution at vitreous carbon was studied, at room temperature, by cyclic voltammetry and potentiostatic
- Afonso,Gomes,Carvalho,Alves,Wastin,Gon?alves
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- A U(V) chalcogenide: Synthesis, structure, and characterization of K 2Cu3US5
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The compound K2Cu3US5 was obtained by the reaction of K2S, UCl4, CuCl, and S at 973 K. K 2Cu3US5 crystallizes in a new structure type in space group Cmcm of the orthorhombic system in a cell of dimensions a = 3.9374(6) A, b = 13.813(2) A, c = 17.500(3) A, and V = 951.8(2) A3 at 153 K. The structure comprises ∞2[UCu3S52-] slabs separated by K+ cations. The slabs are built from CuS4 tetrahedra and US6 octahedra. Their connectivity differs from other known octahedral/tetrahedral packing patterns. In the temperature range 130-300 K the compound exhibits Curie-Weiss magnetic behavior with μeff = 2.45(8) μB. This result together with both the bond distances and bond valence calculations and the absence of a Cu2+ ESR signal support the formulation of the above compound as K+ 2Cu+3U5+S2-5.
- Gray, Danielle L.,Backus, Lisa A.,Von Nidda, Hans-Albrecht Krug,Skanthakumar,Loidl, Alois,Soderholm,Ibers, James A.
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- ELECTRON DIFFRACTION BY URANIUM TETRACHLORIDE
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Vapor electron diffraction has been applied to the molecular structure of uranium tetrachloride.The molecule is a distorted tetrahedron (symmetry group C2v) having internuclear distances rg in angstroem r(UCl1) = 2.475(15), r(UCl2) = 2.558(18), r(Cl1-Cl2) = 3.612(6), r(Cl1Cl1') = 3.312(12), r(Cl2Cl2') = 4.178(12).The Cli and Cli' lie in the same plane.The vibrational frequencies have been calculated.
- Ezhov, Yu. S.,Komarov, S. A.,Mikulinskaya, N. M.
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- Energetics of a uranothorite (Th1-xUxSiO4) solid solution
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High-temperature oxide melt solution calorimetric measurements were completed to determine the enthalpies of formation of the uranothorite, (USiO4)x-(ThSiO4)1-x, solid solution. Phase-pure samples with x values of 0, 0.11, 0.21, 0.35, 0.71, and 0.84 were prepared, purified, and characterized by powder X-ray diffraction, electron probe microanalysis, thermogravimetric analysis and differential scanning calorimetry coupled with in situ mass spectrometry, and high-temperature oxide melt solution calorimetry. This work confirms the energetic metastability of coffinite, USiO4, and U-rich intermediate silicate phases with respect to a mixture of binary oxides. However, variations in unit cell parameters and negative excess volumes of mixing, coupled with strongly exothermic enthalpies of mixing in the solid solution, suggest short-range cation ordering that can stabilize intermediate compositions, especially near x = 0.5.
- Guo, Xiaofeng,Szenknect, Stéphanie,Mesbah, Adel,Clavier, Nicolas,Poinssot, Christophe,Wu, Di,Xu, Hongwu,Dacheux, Nicolas,Ewing, Rodney C.,Navrotsky, Alexandra
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p. 7117 - 7124
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- Electrochemical behavior and some thermodynamic properties of UCl 4 and UCl3 dissolved in a LiCl-KCl eutectic melt
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The electrochemical behavior of UCl4, and UCl3 in LiCl-KCl eutectic melt was studied at 723-823 K by different electrochemical methods. Electroreduction of U(IV) in LiCl-KCl melt occurs via two successive steps involving transfer of one and three electrons. The diffusion coefficients of U(IV) and U(III) were determined by linear sweep voltammetry, chronopotentiometry, and chronoamperometry. The values found by these methods are in a good agreement with each other. The standard rate constants for the redox reaction U(IV) + e- → U(III) were calculated from cyclic voltammetry data and for the discharge process U(III) + 3e- → U by using the impedance spectroscopy method. The values of constants testify that the redox process proceeds quasireversibly, mostly under diffusion control, while electrodeposition is mainly controlled by the rate of charge transfer. The formal standard potentials of EU(IV)/U(III)*, E U(IV)/U*, and EU(III)/U* were determined by different electrochemical methods and some thermodynamic properties of UCl 4 and UCl3 dissolved in a LiCl-KCl eutectic melt were calculated. The influence of oxide ions on the electrochemical behavior of the LiCl-KCl-UCl4 melt was studied.
- Kuznetsov,Hayashi,Minato,Gaune-Escard
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p. C203-C212
(2008/10/09)
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- Cyclopentadienyl uranium(IV) β-diketonates and alkoxides
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Cyclopentadienyl (Cp) complexes of uranium(IV) with fluorinated ligands (L), where L=CH3COCHCOCF-3 (TFAA), C4H3SCOCHCOCF3 (TTA), CF3COCHCOCF-3 (HFAA), C3HF6O- (HFP) and C3H3F4O- (TFP) have been prepared and char
- Gill, M. S.,Sagoria, V. S.
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p. 997 - 999
(2007/10/03)
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- Matrix IR spectra of the products from F2, ClF, and Cl2 reactions with pulsed-laser evaporated uranium atoms
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Pulsed Nd:YAG laser ablated uranium atoms were codeposited with F2 and excess Ar onto a CsI window at 12 K. Infrared spectra revealed the presence of several uranium fluorides including the previously characterized UF4, UF5, and UF6. Lower laser energy favored new absorptions at 400, 446, 496, and 561 cm-1. These product absorptions increased stepwise during annealings which permitted diffusion and reaction of the fluorine. Similar studies with ClF produced the above absorptions plus a new band at 554 cm-1 which is tentatively assigned to ClF2-. The first bands appearing at 400 and 446 cm-1 are assigned to UF and UF2, respectively. The 496- and 561-cm-1 bands are tentatively assigned to UF3 and F3-, respectively. Finally, uranium atoms were reacted with Cl2. In addition to several absorptions due to UCl4, a new doublet at 312 and 308 cm-1 is assigned to UCl2.
- Hunt, Rodney D.,Thompson, Craig,Hassanzadeh, Parviz,Andrews, Lester
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p. 388 - 391
(2008/10/08)
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- The uranocene half-sandwich: ([8]Annulene)uranium(IV) dichloride and some derivatives
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A facile synthesis of ([8]annulene)uranium(IV) dichloride (i) has been developed via the reduction of cyclooctatetraene (COT) by UCl3 or through reaction of UCl4, COT, and NaH. The activation parameters for the coordination of trimet
- Boussie, Thomas R.,Moore Jr., Robert M.,Streitwieser, Andrew,Zalkin, Alan,Brennan, John,Smith, Kennith A.
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p. 2010 - 2016
(2008/10/08)
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- FACILE SYNTHESIS OF UCl4 AND ThCl4, METALLOTHERMIC REDUCTIONS OF UCl4 WITH ALKALI METALS AND CRYSTAL STRUCTURE REFINEMENTS OF UCl3, UCl4 AND Cs2UCl6.
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Uranium and thorium tetrachloride (UCl//4 and ThCl//4) were obtained via the ammonium chloride route from UH//3 and thorium metal respectively, with the ternary chlorides (NH//4)//2ICl//6 and (NH//4)//2ThCl//6 acting as intermediates. The crystal structur
- Schleid,Meyer,Morss
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- Thermochemical studies of the gaseous uranium chlorides
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The gaseous uranium halides UCl, UCl2, UCl3, UCl4, and UCl5 were generated under equilibrium conditions using several types of effusive beam sources, and were identified and characterized thermochemically by mass spectrometry.Five independent gaseous equi
- Lau, K. H.,Hildenbrand, D. L.
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p. 1312 - 1317
(2007/10/02)
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- Standard enthalpies of formation of uranium compounds. VIII. UCl3, UCl5, and UCl6
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Enthalpies of solution of UCl3 in H2SO4(aq) have been measured calorimetrically.In the same way enthalpies of solution of UCl5 and UCl6 have been measured in (HCl + FeCl3)(aq) and HCl(aq), respectively.Together with data for the auxiliary reactions, the s
- Cordfunke, E. H. P.,Ouweltjes, W.,Prins, G.
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p. 495 - 502
(2007/10/02)
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- Reactivity of transition metal fluorides. II. Uranium hexafluoride
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Reactions have been studied between uranium hexafluoride and a series of lower fluorides of other elements. The study has also included reaction with a wide range of covalent chlorides. The reactivity of uranium hexafluoride is compared with that of the higher fluorides of d-transition elements, chromium, molybdenum, and tungsten, and considered in the light of uranium as an f-transition element.
- O'Donnell,Stewart,Wilson
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p. 1438 - 1441
(2008/10/08)
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