Vanadium pentafluoride

The compound is exclusively a monomer in the gas phase.{{Cite journal|last1=Brownstein|first1=S.|last2=Latremouille|first2=G.|date=1974-06-15|title=Complex Fluoroanions in Solution. V. Vanadium Pentafluoride|journal=Canadian Journal of Chemistry|volume=52|issue=12|pages=2236–2241|doi=10.1139/v74-323|issn=0008-4042|doi-access=free}} In the gas phase it adopts D_3h symmetric trigonal bipyramidal geometry as indicated by electron diffraction.{{Cite journal|last1=Hagen|first1=Kolbjoern.|last2=Gilbert|first2=Michael M.|last3=Hedberg|first3=Lise.|last4=Hedberg|first4=Kenneth.|date=1982-07-01|title=Molecular structure of gaseous vanadium pentafluoride, VF5|journal=Inorganic Chemistry|volume=21|issue=7|pages=2690–2693|doi=10.1021/ic00137a031|issn=0020-1669}} As a solid, VF₅ forms a polymeric structure with fluoride-bridged octahedral vanadium centers.{{Cite journal|last=Brownstein|first=S.|date=1980-06-01|title=The structure of VF5 in solution|journal=Journal of Fluorine Chemistry|volume=15|issue=6|pages=539–540|doi=10.1016/S0022-1139(00)85231-8}}

The formation enthalpy of VF₅ is -1429.4 ± 0.8 kJ/mol.{{Cite journal|last1=Nikitin|first1=M. I.|last2=Zbezhneva|first2=S. G.|date=2014-12-16|title=Thermochemistry of vanadium fluorides: The formation enthalpies of vanadium fluorides|journal=High Temperature|language=en|volume=52|issue=6|pages=809–813|doi=10.1134/S0018151X14060108|s2cid=98343689|issn=0018-151X}}

It is the only known pentahalide of vanadium.

Vanadium pentafluoride can be prepared by fluorination of vanadium metal:{{cite journal | doi = 10.1021/ja01576a023 | title = The Preparation and Properties of Vanadium Pentafluoride | year = 1957 | last1 = Trevorrow | first1 = L. E. | last2 = Fischer | first2 = J. | last3 = Steunenberg | first3 = R. K. | journal = Journal of the American Chemical Society | volume = 79 | issue = 19 | pages = 5167–5168}}

: 2 V + 5 F₂ → 2 VF₅

Alternatively, disproportionation of vanadium tetrafluoride yields equal amounts of the solid trifluoride and the volatile pentafluoride:{{cite journal | doi =10.1002/cber.19110440379 | title =Vanadinfluoride | year =1911 | last1 =Ruff | first1 =Otto |authorlink1=Otto Ruff| last2 =Lickfett | first2 =Herbert | journal =Berichte der Deutschen Chemischen Gesellschaft | volume =44 | issue =3 | pages =2539–2549| url =https://zenodo.org/record/1426465 }}{{cite journal | doi =10.1039/TF9635902706 | title =Thermochemistry of vanadium fluorides | year =1963 | last1 =Cavell | first1 =R. G. | last2 =Clark | first2 =H. C. | journal =Transactions of the Faraday Society | volume =59 | pages =2706}}

:2 VF₄ → VF₃ + VF₅

This 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.{{Cite journal|last1=Clark|first1=H. C.|last2=Emeléus|first2=H. J.|title=40. Chemical reactions with vanadium, niobium, and tantalum pentafluorides|journal=J. Chem. Soc.|language=en|pages=190–195| doi=10.1039/jr9580000190|date=January 1958}}

Interest in this highly corrosive compound began in the fifties when there were extensive studies of its physicochemical properties.{{Cite journal|last1=Krasil'nikov|first1=V. A.|last2=Andreev|first2=G. G.|last3=Karelin|first3=A. I.|last4=Guzeeva|first4=T. I.|last5=Furin|first5=G. G.|last6=Bardin|first6=V. V.|last7=Avramenko|first7=A. A.|date=1995-10-17|title=ChemInform Abstract: Synthesis and Use of Vanadium Pentafluoride.|journal=ChemInform|language=en|volume=26|issue=42|pages=no|doi=10.1002/chin.199542022|issn=1522-2667}} 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 HF

Then to the binary oxide:

:2 VOF₃ + 3 H₂O → V₂O₅ + 6 HF

Hydrolysis 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:Nikolsky, B. P. [Никольский, Б.П.] et al, eds. (1971). Справочник химика [The Chemist's Handbook] {{in lang|ru}}. 3rd (corrected) ed. Leningrad: Khimiya.Knunyants, I. L. [Кнунянц, И.Л.] et al, eds. (1995). Химическая энциклопедия [A Chemical Encyclopedia] {{in lang|ru}}. Moscow: Soviet Encyclopedias. {{ISBN|978-5-85270-092-6}}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] {{in lang|ru}}. 3rd (corrected) ed. Мoscow: Khimiya. {{ISBN|978-5-7245-1163-6}}

:VF₅ + KF → KVF₆

Vanadium pentafluoride is a weaker acid and mainly undergoes oxidative and fluorinating reactions.{{Cite journal|last1=Fowler|first1=Brian R.|last2=Moss|first2=Kenneth C.|date=1979-12-01|title=An N.M.R. study of the solution chemistry of vanadium pentafluoride|journal=Journal of Fluorine Chemistry|volume=14|issue=6|pages=485–494|doi=10.1016/S0022-1139(00)82524-5}}

The compound fluorinates unsaturated polyfluoroolefins into polyfluoroalkanes.

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

{{reflist}}

• Arnold F. Holleman, Nils Wiberg: Lehrbuch der Anorganischen Chemie, 102. Auflage, de Gruyter, Berlin 2007, S. 1545, {{ISBN|978-3-11-017770-1}}.

{{Vanadium compounds}}

{{fluorides}}

Category:Vanadium(V) compounds

Category:Fluorides

Category:Metal halides

Category:Fluorinating agents

Category:Inorganic polymers

Category:Coordination polymers