Uranium pentafluoride

β form
3D model (JSmol)
ECHA InfoCard 100.033.991 Edit this at Wikidata
EC Number
  • 237-405-9
  • InChI=1S/5FH.U/h5*1H;/q;;;;; 5/p-5 ☒N
  • InChI=1/5FH.U/h5*1H;/q;;;;;+2/p-5
  • [U+5].[F-].[F-].[F-].[F-].[F-]
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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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.

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]

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]

Structure of molecular UF5.


  1. ^ Gordon W. Halstead, P. Gary Eller "Uranium(V) Fluorides and Alkoxides" Inorganic Syntheses 1982, volume 21, 162. doi:10.1002/9780470132524.ch35
  2. ^ Eller, P. G.; Larson, A. C.; Peterson, J. R.; Ensor, D. D.; Young, J. P. (1979). "Crystal Structures of α-UF5 and U2F9 and Spectral Characterization of U2F9". Inorganica Chimica Acta. 37 (2): 129–133. doi:10.1016/S0020-1693(00)95530-0.
  3. ^ a b Howard, C. J.; Taylor, J. C.; Waugh, A. B. (1982). "Crystallographic Parameters in α-UF5 and U2F9 by Multiphase Refinement of High-Resolution Neutron Powder Data". Journal of Solid State Chemistry. 45 (3): 396–398. Bibcode:1982JSSCh..45..396H. doi:10.1016/0022-4596(82)90185-2.
  4. ^ Taylor, J. C.; Waugh, A. B. (1980). "Neutron Diffraction Study of β-Uranium Pentafluoride Between 77 and 403 K". Journal of Solid State Chemistry. 35 (2): 137–147. Bibcode:1980JSSCh..35..137T. doi:10.1016/0022-4596(80)90485-5.
  5. ^ Onoe, J.; Nakamatsu, H.; Mukoyama, T.; Sekine, R.; Adachi, H.; Takeuchi, K. (1997). "Structure and Bond Nature of the UF5 Monomer". Inorg. Chem. 36 (9): 1934–1938. doi:10.1021/ic961237s. PMID 11669800.