Silver(II) fluoride

Chembox new
Name = Silver(II) fluoride
ImageFile = Silver(II)-fluoride-3D-ionic.png ImageName = Silver(II) fluoride
IUPACName = silver(II) fluoride
OtherNames = silver difluoride
Section1 = Chembox Identifiers
CASNo = 7775-41-9
Section2 = Chembox Properties
Formula = AgF₂
MolarMass = 145.865 g/mol
Appearance = white or grey crystalline powder, hygroscopic
Density = 4.58 g/cm³
Solubility = Decomposes, violently
MeltingPt = 690 °C (963 K)
BoilingPt = decomposes at 700 °C (973 K)
Section3 = Chembox Structure
MolShape = linear
Coordination = tetragonally elongated
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
with water, powerful oxidizer
Section8 = Chembox Related
OtherCpds = Silver(I) fluoride, AgF
Silver subfluoride, Ag₂F
Silver(I,III) oxide, AgO
Silver(I) oxide, Ag₂O

Silver(II) fluoride is a chemical compound with the formula AgF₂. 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

AgF₂ can be synthesized by fluorinating Ag₂O with elemental fluorine. Also, at 200 °C (473 K) elemental fluorine will react with AgF or AgCl to produce AgF₂.ref|ISref|encyclo

As a strong fluorinating agent, AgF₂ should be stored in Teflon, a passivated metal container, or a quartz tube. It is light sensitive.

AgF₂ can be purchased from various suppliers, the demand being less than 100 kg/year. While laboratory experiments find use for AgF₂, it is too expensive for large scale industry use. In 1993, AgF₂ cost between 1000-1400 US dollars per kg.

Composition and structure

AgF₂ 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 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^I [Ag^IIIF₄] , which would be similar to silver oxide. Neutron diffraction studies, however, confirmed its description as silver(II). The Ag^I [Ag^IIIF₄] was found to be present at high temperatures, but it was unstable with respect to AgF₂.ref|structure

In the gas phase, AgF₂ is believed to have D_∞h symmetry.

Approximately 14 kcal/mol (59 kJ/mol) separate the ground and first states. The compound is paramagnetic, but it becomes ferromagnetic at temperatures below −110 °C (163 K).

Uses

AgF₂ is a strong fluorinating and oxidation agent. Illustrative applications are listed below.

* Fluoronation and preparation of organic perfluorocompounds ref|rxnsThis 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) CZ₃H + 2 AgF₂ → CZ₃F +HF + 2 AgF:2) CZ₃X + 2AgF₂ → CZ₃F +X₂ + 2 AgF:3) Z₂C=CZ₂ + 2 AgF₂ → Z₂CFCFZ₂ + 2 AgF Similar transformations can also be effected using other high valence metallic fluorides such as CoF₃, MnF₃, CeF₄, and PbF₄.

* Fluorinations of aromatic compounds is readily achieved, but selective monofluorinations are more difficult:ref|monof:C₆H₆ + 2 AgF₂ → C₆H₅F + 2 AgF + HF

*Oxidation of xenon ref|Xenon. This reaction, which can be explosive, proceeds in anhydrous HF solutions producing XeF₂.

*AgF₂ oxidizes carbon monoxide to carbonyl fluoride.

References

# Priest, H. F. “Anhydrous Metal Fluorides” Inorganic Syntheses McGraw-Hill: New York, 1950; Vol. 3, pages 171-183.
# "Encyclopedia of Chemical Technology." Kirk-Othermer. Vol.11, 4th Ed. (1991)
# J.T. Wolan, G.B. Hoflund. "Surface Characterization Study of AgF and AgF₂ Powders Using XPS and ISS," "Applied Surface Science." 125, (1998).
# 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).
# 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).
# Zweig, A.; Fischer, R. G.; Lancaster, J. "New Methods for Selective Monofluorination of Aromatics Using Silver Difluoride," Journal of Organic Chemistry volume 45, (1980).
# 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]