Uranium pentafluoride

Uranium pentafluoride
Identifiers
β form
CAS Number	13775-07-0^Y
3D model (JSmol)	Interactive image
ChemSpider	75545^Y
ECHA InfoCard	100.033.991
EC Number	237-405-9
PubChem CID	83723
UNII	VG7WW26FTQ^Y
CompTox Dashboard (EPA)	DTXSID7065625
InChI InChI=1S/5FH.U/h51H;/q;;;;; 5/p-5^N Key: JNVYCANIFQDNST-UHFFFAOYSA-I^N InChI=1/5FH.U/h51H;/q;;;;;+2/p-5 Key: YKLDBRIIJYAXGS-AACRGIKGAA
SMILES [U+5].[F-].[F-].[F-].[F-].[F-]
Properties
Chemical formula	UF₅
Molar mass	333.02 g/mol
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). N verify (what is ^YN ?) Infobox references

Chemical compound

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]

References

^ Gordon W. Halstead, P. Gary Eller "Uranium(V) Fluorides and Alkoxides" Inorganic Syntheses 1982, volume 21, 162. doi:10.1002/9780470132524.ch35
^ 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.
^ ^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.
^ 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.
^ 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.