Uranium pentafluoride
Chemical compound
From Wikipedia, the free encyclopedia
Uranium pentafluoride is the inorganic compound with the chemical formula UF5. It is a pale yellow paramagnetic solid. The compound has attracted interest because it is related to uranium hexafluoride, which is widely used to produce uranium fuel. It crystallizes in two polymorphs, called α- and β-UF5.
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3D model (JSmol) |
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| ECHA InfoCard | 100.033.991 |
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CompTox Dashboard (EPA) |
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| Properties | |
| UF5 | |
| Molar mass | 333.02 g/mol |
| Appearance | Pale yellow crystalline solid |
| Density | 5.823 g/cm3 (alpha polymorph) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Synthesis and structure
Uranium pentafluoride is an intermediate in the conversion of uranium tetrafluoride to volatile UF6:
- 2 UF4 + F2 → 2 UF5
- 2 UF5 + F2 → 2 UF6
It can be produced by reduction of the hexafluoride with carbon monoxide at elevated temperatures.[1]
- 2 UF6 + CO → 2 UF5 + COF2
Other reducing agents have been examined.[2]
It can also be produced by various molecular laser isotope separation methods.
The α form is a linear coordination polymer consisting of chains of octahedral uranium centers in which one of the five fluoride anion forms a bridge to the next uranium atom.[3] The structure is reminiscent of that for vanadium pentafluoride.
In the β form, the uranium centers adopt a square antiprismatic structure.[4] The β polymorph gradually converts to α at 130 °C.[3]
Monomeric UF5
Of theoretical interest, molecular UF5 can be generated as a transient monomer by UV-photolysis of uranium hexafluoride. It is thought to adopt a square pyramidal geometry.[5]
