Vanadium pentafluoride explained

Vanadium(V) fluoride is the inorganic compound with the chemical formula VF₅. It is a colorless volatile liquid that freezes near room temperature. It is a highly reactive compound, as indicated by its ability to fluorinate organic substances.^[1]

Properties and structure

The compound is exclusively a monomer in the gas phase.^[2] In the gas phase it adopts D_3h symmetric trigonal bipyramidal geometry as indicated by electron diffraction.^[3] As a solid, VF₅ forms a polymeric structure with fluoride-bridged octahedral vanadium centers.^[4]

The formation enthalpy of VF₅ is -1429.4 ± 0.8 kJ/mol.^[5]

It is the only known pentahalide of vanadium.

Synthesis

Vanadium pentafluoride can be prepared by fluorination of vanadium metal:^{[6] [7] [9] [10]}

Characteristics and reactivity

Interest in this highly corrosive compound began in the fifties when there were extensive studies of its physicochemical properties.^[12] It is a powerful fluorinating and oxidizing agent. It oxidizes elemental sulfur to sulfur tetrafluoride:.

S + 4 VF₅ → 4 VF₄ + SF₄

Like other electrophilic metal halides, it hydrolyzes, first to the oxyhalide:

VF₅ + H₂O → VOF₃ + 2 HFThen to the binary oxide:

2 VOF₃ + 3 H₂O → V₂O₅ + 6 HFHydrolysis is accelerated in the presence of base. Despite its tendency to hydrolyze, it can be dissolved in alcohols.

It is a Lewis acid, as illustrated by its formation of the hexafluorovanadate:^{[13] [14] [15]}

VF₅ + KF → KVF₆

Vanadium pentafluoride is a weaker acid and mainly undergoes oxidative and fluorinating reactions.^[16]

The compound fluorinates unsaturated polyfluoroolefins into polyfluoroalkanes.

The compound dissolves without reaction in liquid Cl₂ and Br₂. VF₅ is moderately soluble in HF.

Other reading

• Arnold F. Holleman, Nils Wiberg: Lehrbuch der Anorganischen Chemie, 102. Auflage, de Gruyter, Berlin 2007, S. 1545, .

Notes and References

1. Canterford. J. H.. O'Donnell. Thomas A.. 1967-03-01. Reactivity of transition metal fluorides. IV. Oxidation-reduction reactions of vanadium pentafluoride. Inorganic Chemistry. 6. 3. 541–544. 10.1021/ic50049a025. 0020-1669.
2. Brownstein. S.. Latremouille. G.. 1974-06-15. Complex Fluoroanions in Solution. V. Vanadium Pentafluoride. Canadian Journal of Chemistry. 52. 12. 2236–2241. 10.1139/v74-323. 0008-4042. free.
3. Hagen. Kolbjoern.. Gilbert. Michael M.. Hedberg. Lise.. Hedberg. Kenneth.. 1982-07-01. Molecular structure of gaseous vanadium pentafluoride, VF5. Inorganic Chemistry. 21. 7. 2690–2693. 10.1021/ic00137a031. 0020-1669.
4. Brownstein. S.. 1980-06-01. The structure of VF5 in solution. Journal of Fluorine Chemistry. 15. 6. 539–540. 10.1016/S0022-1139(00)85231-8.
5. Nikitin. M. I.. Zbezhneva. S. G.. 2014-12-16. Thermochemistry of vanadium fluorides: The formation enthalpies of vanadium fluorides. High Temperature. en. 52. 6. 809–813. 10.1134/S0018151X14060108. 98343689. 0018-151X.
6. 10.1021/ja01576a023 . The Preparation and Properties of Vanadium Pentafluoride . 1957 . Trevorrow . L. E. . Fischer . J. . Steunenberg . R. K. . Journal of the American Chemical Society . 79 . 19 . 5167–5168.
7. 10.1002/cber.19110440379 . Vanadinfluoride . 1911 . Ruff . Otto . Otto Ruff. Lickfett . Herbert . Berichte der Deutschen Chemischen Gesellschaft . 44 . 3 . 2539–2549.

8. 2 V + 5 F₂ → 2 VF₅Alternatively, disproportionation of vanadium tetrafluoride yields equal amounts of the solid trifluoride and the volatile pentafluoride:^[7]

9. 10.1039/TF9635902706 . Thermochemistry of vanadium fluorides . 1963 . Cavell . R. G. . Clark . H. C. . Transactions of the Faraday Society . 59 . 2706.
10. Clark. H. C.. Emeléus. H. J.. 40. Chemical reactions with vanadium, niobium, and tantalum pentafluorides. J. Chem. Soc.. en. 190–195. 10.1039/jr9580000190. January 1958.

11. 2 VF₄ → VF₃ + VF₅This conversion is conducted at 650 °C. It can also be synthesized by using elemental fluorine to fluorinate industrial concentrates and raw materials so as to produce VF₅ on an industrial scale. VF₅ can be synthesized from the reaction of raw materials such as metallic Vanadium, ferrovanadium, vanadium (V) oxide and vanadium tetrafluoride with elemental fluorine.

    VF₅ ionises in the liquid state as reflected by the high values of Trouton's constant and electrical conductivities.^[10]

12. Krasil'nikov. V. A.. Andreev. G. G.. Karelin. A. I.. Guzeeva. T. I.. Furin. G. G.. Bardin. V. V.. Avramenko. A. A.. 1995-10-17. ChemInform Abstract: Synthesis and Use of Vanadium Pentafluoride.. ChemInform. en. 26. 42. no. 10.1002/chin.199542022. 1522-2667.
13. [Boris Nikolsky|Nikolsky, B. P.]
14. [Ivan Knunyants|Knunyants, I. L.]
15. Lidin, R. A. [Лидин Р.А.] et al (2000). Химические свойства неорганических веществ: Учеб. пособие для вузов [''Chemical Properties of Inorganic Substances: A University Textbook''] . 3^rd (corrected) ed. Мoscow: Khimiya.
16. Fowler. Brian R.. Moss. Kenneth C.. 1979-12-01. An N.M.R. study of the solution chemistry of vanadium pentafluoride. Journal of Fluorine Chemistry. 14. 6. 485–494. 10.1016/S0022-1139(00)82524-5.