Loading AI tools
Chemical compound From Wikipedia, the free encyclopedia
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.
Names | |
---|---|
IUPAC name
Uranium(VI) chloride | |
Other names
Uranium hexachloride Peruranic chloride | |
Identifiers | |
3D model (JSmol) |
|
ChemSpider | |
PubChem CID |
|
| |
| |
Properties | |
UCl6 | |
Molar mass | 450.745 g/mol |
Appearance | dark green crystalline solid |
Density | 3.6 g/cm3 |
Melting point | 177 °C (351 °F; 450 K) |
Related compounds | |
Other anions |
Uranium hexafluoride |
Other cations |
Tungsten hexachloride |
Related uranium chlorides |
|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|
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.
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.
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.
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).[6]
When UCl6 is reacted with purified anhydrous liquid hydrogen fluoride (HF) at room temperature produces UF5.[6]
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.[7] 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.[8]
Step 1: 2 UCl4 + Cl2 → 2 UCl5
Step 2: 2 UCl5 + Cl2 → 2 UCl6
Overall Reaction: UCl4 + Cl2 → UCl6
Seamless Wikipedia browsing. On steroids.
Every time you click a link to Wikipedia, Wiktionary or Wikiquote in your browser's search results, it will show the modern Wikiwand interface.
Wikiwand extension is a five stars, simple, with minimum permission required to keep your browsing private, safe and transparent.