Silver(II) fluoride
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{{Chembox new
| Name = Silver(II) fluoride
| ImageFile = Silver(II)-fluoride-3D-ionic.png
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| ImageName = Silver(II) fluoride
| IUPACName = silver(II) fluoride
| OtherNames = silver difluoride
| Section1 = {{Chembox Identifiers
| CASNo = 7775-41-9
}}
| Section2 = {{Chembox Properties
| Formula = AgF<sub>2</sub>
| MolarMass = 145.865 g/mol
| Appearance = white or grey crystalline powder, [[hygroscopic]]
| Density = 4.58 g/cm<sup>3</sup>
| Solubility = Decomposes, violently
| MeltingPt = 690 °C (963 K)
| BoilingPt = decomposes at 700 °C (973 K)
}}
| Section3 = {{Chembox Structure
| MolShape = linear
| Coordination = tetragonally elongated<br />octahedral coordination
| CrystalStruct = orthorhombic
}}
| Section7 = {{Chembox Hazards
| ExternalMSDS = [http://newsearchch.chemexper.com/cheminfo/servlet/org.dbcreator.MainServlet?action=PowerSearch&query=msds._msdsID%3D19659&sort=&target=msds&from=0&realQuery=rn.value%3D%3D%227783-95-1%22&searchTemplate=rn.value%3D%3D%3F&searchValue=7783-95-1&history=off&options=brandqtyoffer&format=ccd MSDS]
| MainHazards = toxic, reacts violently<br />with water, powerful oxidizer
}}<!--
| Other silver(II) [[halide]]s
| no other AgX<sub>2</sub> stable<br />at room temp.
|-
-->
| Section8 = {{Chembox Related
| OtherCpds = [[Silver(I) fluoride|Silver(I) fluoride, AgF]]<br />[[Silver subfluoride|Silver subfluoride, Ag<sub>2</sub>F]]<br />[[Silver(II) oxide|Silver(II) oxide, AgO]]<br />[[Silver(I) oxide|Silver(I) oxide, Ag<sub>2</sub>O]]
}}
}}
'''Silver(II) fluoride''' is a [[chemical compound]] with the [[chemical formula|formula]] AgF<sub>2</sub>. It is a rare example of a silver(II) compound. Silver is usually present in its +1 [[oxidation state]]. It is used as a fluorinating agent.
==Preparation==
AgF<sub>2</sub> can be synthesized by fluorinating Ag<sub>2</sub>O with elemental [[fluorine]]. Also, at 200 °C (473 K) elemental fluorine will react with [[silver(I) fluoride|AgF]] or [[AgCl]] to produce AgF<sub>2</sub>.{{ref|IS}}{{ref|encyclo}}
As a strong fluorinating agent, AgF<sub>2</sub> should be stored in [[Teflon]], a passivated metal container, or a [[quartz]] tube. It is light sensitive.
AgF<sub>2</sub> can be purchased from various suppliers, the demand being less than 100 kg/year. While laboratory experiments find use for AgF<sub>2</sub>, it is too expensive for large scale industry use. In 1993, AgF<sub>2</sub> cost between 1000-1400 [[US dollar]]s per kg.
==Composition and structure==
AgF<sub>2</sub> is a white crystalline powder, but it is usually black/brown due to impurities. The F/Ag ratio for most samples is< 2, typically approaching 1.75 due to contamination with Ag and [[oxygen|oxides]] and [[carbon]]. {{ref|XPS}}
For some time, it was doubted silver was actually in the 2+ oxidation state rather in some combination of states such as Ag<sup>I</sup>[Ag<sup>III</sup>F<sub>4</sub>], which would be similar to [[silver oxide]]. [[Neutron diffraction]] studies, however, confirmed its description as silver(II). The Ag<sup>I</sup>[Ag<sup>III</sup>F<sub>4</sub>] was found to be present at high temperatures, but it was unstable with respect to AgF<sub>2</sub>.{{ref|structure}}
In the gas phase, AgF<sub>2</sub> is believed to have D<sub>∞h</sub> [[symmetry group|symmetry]].
Approximately 14 [[kilocalorie|kcal]]/[[mole (unit)|mol]] (59 [[kilojoule|kJ]]/mol) separate the [[ground state|ground]] and first [[excited state|state]]s. The compound is [[paramagnetic]], but it becomes [[ferromagnetic]] at temperatures below −110 °C (163 K).
==Uses==
AgF<sub>2</sub> is a strong fluorinating and oxidation agent. Illustrative applications are listed below.
* Fluoronation and preparation of organic perfluorocompounds {{ref|rxns}}
This type of reaction can occur in three different ways (here Z refers to any element or group attached to carbon, X is a [[halogen]]):
:1) CZ<sub>3</sub>H + 2 AgF<sub>2</sub> → CZ<sub>3</sub>F +HF + 2 AgF
:2) CZ<sub>3</sub>X + 2AgF<sub>2</sub> → CZ<sub>3</sub>F +X<sub>2</sub> + 2 AgF
:3) Z<sub>2</sub>C=CZ<sub>2</sub> + 2 AgF<sub>2</sub> → Z<sub>2</sub>CFCFZ<sub>2</sub> + 2 AgF
Similar transformations can also be effected using other high [[Valence (chemistry)|valence]] metallic fluorides such as [[cobalt(III) fluoride|CoF<sub>3</sub>]], MnF<sub>3</sub>, CeF<sub>4</sub>, and PbF<sub>4</sub>.
* [[Fluorination]]s of [[aromatic]] compounds is readily achieved, but selective monofluorinations are more difficult:{{ref|monof}}
:C<sub>6</sub>H<sub>6</sub> + 2 AgF<sub>2</sub> → C<sub>6</sub>H<sub>5</sub>F + 2 AgF + HF
*[[Oxidation]] of [[xenon]] {{ref|Xenon}}. This reaction, which can be explosive, proceeds in [[anhydrous]] HF solutions producing XeF<sub>2</sub>.
*AgF<sub>2</sub> oxidizes [[carbon monoxide]] to [[carbonyl fluoride]].
==References==
{{Citationstyle|date=September 2007}}
{{reflist}}
#{{note|IS}} Priest, H. F. “Anhydrous Metal Fluorides” Inorganic Syntheses McGraw-Hill: New York, 1950; Vol. 3, pages 171-183.
#{{note|encyclo}} ''Encyclopedia of Chemical Technology.'' Kirk-Othermer. Vol.11, 4th Ed. ('''1991''')
#{{note|XPS}} J.T. Wolan, G.B. Hoflund. "Surface Characterization Study of AgF and AgF<sub>2</sub> Powders Using XPS and ISS," ''Applied Surface Science.'' 125, ('''1998''').
#{{note|structure}} Hans-Christian Miller, Axel Schultz, and Magdolna Hargittai. "Structure and Bonding in Silver Halides: A Quantum...X=F, Cl, Br, I," [[Journal of the American Chemical Society]] 127(22), ('''2005''').
# {{note|rxns}} Rausch, D.; Davis, r.; Osborne, D. W. "The Addition of Fluorine to Halogenated Olefins by Means of Metal Fluorides," [[Journal of Organic Chemistry]] volume 28, pp. 494-497, Jul. ('''1962''').
#{{note|monof}} Zweig, A.; Fischer, R. G.; Lancaster, J. "New Methods for Selective Monofluorination of Aromatics Using Silver Difluoride," [[Journal of Organic Chemistry]] volume 45, ('''1980''').
# {{note|Xenon}} Levec, J.; Slivnik, J.; Zemva, B. "On the Reaction Between Xenon and Fluorine," ''Journal of Inorganic Nuclear Chemistry'' Volume 36, ('''1974''').
==External links==
*[http://www.npi.gov.au/database/substance-info/profiles/44.html National Pollutant Inventory Fluoride and compounds fact sheet]
*[http://www.webelements.com/webelements/compounds/text/Ag/Ag1F2-7783951.html WebElements Silver(II) Fluoride]
*[http://www.chem.ox.ac.uk/inorganicchemistry3/Ag/AgF2.html Structure graphic]
[[Category:Fluorides]]
[[Category:Silver compounds]]
[[Category:Metal halides]]
[[de:Silber(II)-fluorid]]
[[fr:Difluorure d'argent]]
[[zh:二氟化银]]