Uranium hexachloride

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Uranium hexachloride
Uranium Hexachloride.png
Names
IUPAC name
Uranium(VI) chloride
Other names
Uranium hexachloride
Peruranic chloride
Identifiers
  • 161280-02-0
3D model (JSmol)
ChemSpider
PubChem CID
  • InChI=1S/6ClH.U/h6*1H;/p-6
    Key: XFCORTPUZRSUIZ-UHFFFAOYSA-H
  • [Cl-].[Cl-].[Cl-].[Cl-].[Cl-].[Cl-].[U]
Properties
UCl6
Molar mass 450.745 g/mol
Appearancedark green crystalline solid
Density 3600 kg/m3
Melting point 177 °C (351 °F; 450 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Uranium hexachloride (UCl6) is an inorganic chemical compound of uranium in the +6 oxidation state. [1] [2] UCl6 is a metal halide composed of uranium and chlorine. It is a multi-luminescent dark green crystalline solid with a vapor pressure between 1-3 mmHg at 373.15 K. [3] UCl6 is stable in a vacuum, dry air, nitrogen and helium at room temperature. It is soluble in carbon tetrachloride (CCl4). Compared to the other uranium halides, little is known about UCl6.

Contents

Structure and Bonding

Uranium hexachloride has an octahedral geometry, with point group Oh. Its lattice (dimensions: 10.95 ± 0.02 Å x 6.03 ± 0.01 Å) is hexagonal in shape with three molecules per cell; the average theoretical U-Cl bond is 2.472 Å long (the experimental U-Cl length found by X-ray diffraction is 2.42 Å), [4] and the distance between two adjacent chlorine atoms is 3.65 Å.

Chemical Properties

Uranium hexachloride is a highly hygroscopic compound and decomposes readily when exposed to ordinary atmospheric conditions. [5] therefore it should be handled in either a vacuum apparatus or in a dry box.

Thermal decomposition

UCl6 is stable up to temperatures between 120 °C and 150 °C. The decomposition of UCl6 results in a solid phase transition from one crystal form of UCl6 to another more stable form. [6] However, the decomposition of gaseous UCl6 produces UCl5. The activation energy for this reaction is about 40 kcal per mole.

2 UCl6 (g) → 2 UCl5 (s) + Cl2 (g)

Solubility

UCl6 is not a very soluble compound. It dissolves in CCl4 to give a brown solution. It is slightly soluble in isobutyl bromide and in fluorocarbon (C7F16). [7]

SolventsTemperature (°C)Grams of UCl6/100g of solution
CCl4 −182.64
CCl4 04.9
CCl4 207.8
6.6% Cl2  : 93.4% CCl4 −202.4
12.5% Cl2  : 87.5% CCl4 −202.23
12.5% Cl2  : 87.5% CCl4 03.98
Liquid Cl2 −332.20
CH3Cl −241.16
Benzene 80 Insoluble
Freon 113 451.83

Reaction with hydrogen fluoride

When UCl6 is reacted with purified anhydrous liquid hydrogen fluoride (HF) at room temperature produces UF5. [8]

2 UCl6+ 10 HF → 2 UF5 + 10 HCl + Cl2

Synthesis

Uranium hexachloride can be synthesized from the reaction of uranium trioxide (UO3) with a mixture of liquid CCl4 and hot chlorine (Cl2). The yield can be increased if the reaction carried out in the presence of UCl5. [9] The UO3 is converted to UCl5, which in turn reacts with the excess Cl2 to form UCl6. It requires a substantial amount of heat for the reaction to take place; the temperature range is from 65 °C to 170 °C depending on the amount of reactant (ideal temperature 100 °C - 125 °C). The reaction is carried out in a closed gas-tight vessel (for example a glovebox) that can withstand the pressure that builds up.

Step 1: 2 UO3 + 5 Cl2 → 2 UCl5 + 3 O2

Step 2: 2 UCl5 + Cl2 → 2 UCl6

Overall reaction: 2 UO3 + 6 Cl2 → 2 UCl6 + 3 O2

This metal hexahalide can also be synthesized by blowing Cl2 gas over sublimed UCl4 at 350 °C. [10]

Step 1: 2 UCl4 + Cl2 → 2 UCl5

Step 2: 2 UCl5 + Cl2 → 2 UCl6

Overall Reaction: UCl4 + Cl2 → UCl6

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Dichlorine monoxide Chemical compound

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Tantalum(V) chloride Chemical compound

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Hafnium tetrachloride Chemical compound

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Uranium trioxide Chemical compound

Uranium trioxide (UO3), also called uranyl oxide, uranium(VI) oxide, and uranic oxide, is the hexavalent oxide of uranium. The solid may be obtained by heating uranyl nitrate to 400 °C. Its most commonly encountered polymorph, γ-UO3, is a yellow-orange powder.

Zirconium(IV) chloride Chemical compound

Zirconium(IV) chloride, also known as zirconium tetrachloride, (ZrCl4) is an inorganic compound frequently used as a precursor to other compounds of zirconium. This white high-melting solid hydrolyzes rapidly in humid air.

Uranyl chloride Chemical compound

Uranyl chloride refers to inorganic compounds with the formula UO2Cl2(H2O)n where n = 0, 1, or 3. These are yellow-colored solids.

Uranium tetrachloride Chemical compound

Uranium tetrachloride is the inorganic compound with the formula UCl4. It is a hygroscopic olive-green solid. It was used in the electromagnetic isotope separation (EMIS) process of uranium enrichment. It is one of the main starting materials for organouranium chemistry.

Uranium(III) chloride Chemical compound

Uranium(III) chloride, UCl3, is a chemical compound that contains the earth metal uranium and chlorine. UCl3 is used mostly to reprocess spent nuclear fuel. Uranium(III) chloride is synthesized in various ways from uranium(IV) chloride; however, UCl3 is less stable than UCl4.

Molybdenum(V) chloride Chemical compound

Molybdenum(V) chloride is the inorganic compound with the formula [MoCl5]2. This dark volatile solid is used in research to prepare other molybdenum compounds. It is moisture-sensitive and soluble in chlorinated solvents. Usually called molybdenum pentachloride, it is in fact a dimer with the formula Mo2Cl10.

Tungsten hexachloride is the chemical compound of tungsten and chlorine with the formula WCl6. This dark violet blue species exists as a volatile solid under standard conditions. It is an important starting reagent in the preparation of tungsten compounds. Other examples of charge-neutral hexachlorides are ReCl6 and MoCl6. The highly volatile WF6 is also known.

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Thorium(IV) chloride Chemical compound

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Uranium nitride Chemical compound

Uranium nitride is any of a family of several ceramic materials: uranium mononitride (UN), uranium sesquinitride (U2N3) and uranium dinitride (UN2). The word nitride refers to the −3 oxidation state of the nitrogen bound to the uranium.

Metal halides

Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. Covalently bonded metal halides may be discrete molecules, such as uranium hexafluoride, or they may form polymeric structures, such as palladium chloride.

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Uranium pentachloride is an inorganic chemical compound composed of uranium in the +5 oxidation state and five chlorine atoms.

References

  1. Zachariasen, W. H. (1948). "Crystal chemical studies of the 5f-series of elements. V. The crystal structure of uranium hexachloride". Acta Crystallographica. 1 (6): 285–287. doi:10.1107/S0365110X48000788.
  2. Taylor, J. C.; Wilson, P. W. (1974). "Neutron and X-ray powder diffraction studies of the structure of uranium hexachloride". Acta Crystallographica Section B. 30 (6): 1481. doi:10.1107/S0567740874005115.
  3. Van Dyke, R. E.; Evers, E. C. (1955). "Preparation of Uranium Hexachloride". Google Patents: 2.
  4. Batista, E. R.; Martin, R. L.; Hay, P. J. (2004). "Density Functional Investigations of the Properties and Thermodynamics of UFn and UCln (n=1,...,6)". J. Chem. Phys. 121 (22): 11104–11. doi:10.1063/1.1811607. PMID   15634063.
  5. Lipkin, D.; Wessman, S. (1955). "Process and Apparatus for protecting Uranium hexachloride from Deterioration and Contamination". Google Patents: 2.
  6. Katz, J.J.; Rabinowitch,E. (1951). The Chemistry of Uranium. Ann Arbor: The McGraw-Hill Book Company.
  7. Katz,J.J; Rabinowitch,E. (1951). The Chemistry of Uranium. Ann Arbor: The McGraw-Hill Book Company.
  8. Katz,J.J; Rabinowitch,E. (1951). The Chemistry of Uranium. Ann Arbor: The McGraw-Hill Book Company.
  9. Van Dyke, R. E.; Evers, E. C. (1955). "Preparation of Uranium Hexachloride". Google Patents: 2.
  10. Thornton, G.; Edelstein, N.; Rösch, N.; Woodwark, D.R.; Edgell, R.G. (1979). "The Electronic Structure of UCl6: Photoelectron Spectra and Scattered Wave Xα Calculations". J. Chem. Phys. 70 (11): 6. Bibcode:1979JChPh..70.5218T. doi:10.1063/1.437313.