Silver(II) fluoride

{{chembox | Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 464391669 | Name = Silver(II) fluoride | ImageFile = Silver(II)-fluoride-3D-ionic.png | ImageName = Silver(II) fluoride | ImageFile2 = Silver(II) fluoride.jpg | IUPACName = silver(II) fluoride | OtherNames = silver difluoride |Section1={{Chembox Identifiers | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 10802085 | InChI = 1/Ag.2FH/h;2*1H/q+2;;/p-2 | InChIKey = KWVVTSALYXIJSS-NUQVWONBAP | SMILES = [Ag+2].[F-].[F-] | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/Ag.2FH/h;2*1H/q+2;;/p-2 | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = KWVVTSALYXIJSS-UHFFFAOYSA-L | CASNo_Ref = {{cascite|correct|CAS}} | CASNo = 7783-95-1 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = 372MAR8LH9 | PubChem = 82221 | EINECS = 232-037-5 }} |Section2={{Chembox Properties | Formula = AgF₂ | MolarMass = 145.865 g/mol | Appearance = white or grey crystalline powder, hygroscopic | Density = 4.58 g/cm³ | Solubility = Decomposes | MeltingPtC = 690 | BoilingPtC = 700 | BoilingPt_notes = (decomposes) }} |Section3={{Chembox Structure | MolShape = linear | Coordination = tetragonally elongated<br />octahedral coordination | CrystalStruct = orthorhombic }} |Section7={{Chembox Hazards | ExternalSDS = [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 | NFPA-F = 0 | NFPA-H = 3 | NFPA-R = 3 | NFPA-S = W+OX | GHSPictograms = {{GHS03}}{{GHS05}}{{GHS06}} | GHSSignalWord = Danger | HPhrases = {{H-phrases|272|301|302|311|312|314|331|332}} | PPhrases = {{P-phrases|210|220|221|260|261|264|270|271|280|301+310|301+312|301+330+331|302+352|303+361+353|304+312|304+340|305+351+338|310|311|312|321|322|330|361|363|370+378|403+233|405|501}} }} |Section8={{Chembox Related | OtherAnions = Silver(I,III) oxide <!-- no other AgX2 stable at room temp. --> | OtherCations = Copper(II) fluoride<br />Palladium(II) fluoride<br />Zinc fluoride<br />Cadmium(II) fluoride<br />Mercury(II) fluoride | OtherCompounds = Silver subfluoride<br />Silver(I) fluoride }} }}

'''Silver(II) fluoride''' is a chemical compound with the formula AgF₂. It is a rare example of a silver(II) compound - silver usually exists in its +1 oxidation state. It is used as a fluorinating agent.

==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>{{cite journal |author1=J.T. Wolan |author2=G.B. Hoflund | title = Surface Characterization Study of AgF and AgF₂ Powders Using XPS and ISS | journal = Applied Surface Science | volume = 125 | year = 1998 | doi = 10.1016/S0169-4332(97)00498-4 | pages = 251 | issue = 3–4|bibcode=1998ApSS..125..251W }}</ref>

For some time, it was doubted that silver was actually in the +2 oxidation state, rather than some combination of states such as Ag^I[Ag^IIIF₄], which would be similar to silver(I,III) 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>{{cite journal |author1=Hans-Christian Miller |author2=Axel Schultz |author3=Magdolna Hargittai |name-list-style=amp | doi = 10.1021/ja051442j | journal = J. Am. Chem. Soc. | volume = 127 | issue = 22 | year = 2005 | title = Structure and Bonding in Silver Halides. A Quantum Chemical Study of the Monomers: Ag2X, AgX, AgX2, and AgX3(X = F, Cl, Br, I) | pages = 8133–45 | pmid = 15926841 |bibcode=2005JAChS.127.8133M }}</ref>

In the gas phase, AgF₂ is believed to have D_∞h symmetry. Per single-crystal X-ray diffraction, the silver atoms are square planar-coordinated in the solid state.<ref>{{Cite journal |last1=Jesih |first1=A. |last2=Lutar |first2=K. |last3=Žemva |first3=B. |last4=Bachmann |first4=B. |last5=Becker |first5=St. |last6=Müller |first6=B. G. |last7=Hoppe |first7=R. |date=1990-01-22 |title=Einkristalluntersuchungen an AgF 2 |url=https://onlinelibrary.wiley.com/doi/10.1002/zaac.19905880110 |journal=Zeitschrift für anorganische und allgemeine Chemie |language=en |volume=588 |issue=1 |pages=77–83 |doi=10.1002/zaac.19905880110 |bibcode=1990ZAACh.588...77J |issn=0044-2313|url-access=subscription }}</ref>

Approximately 14 kcal/mol (59 kJ/mol; 0.61&nbsp;eV/f.u.) separate the ground and first excited states. The compound is paramagnetic, but it becomes ferromagnetic at temperatures below −110&nbsp;°C (163 K).

==Preparation== AgF₂ can be synthesized by fluorinating Ag₂O with elemental fluorine. Also, at 200&nbsp;°C (473 K) elemental fluorine will react with AgF or AgCl to produce AgF₂.<ref>{{cite book | author = Priest, H. F. | year = 1950 | volume = 3 | pages = 171–183 | doi = 10.1002/9780470132340.ch47 | last2 = Swinehert | first2 = Carl F. | title = Inorganic Syntheses | chapter = Anhydrous Metal Fluorides | isbn = 978-0-470-13234-0}}</ref><ref>''Encyclopedia of Chemical Technology.'' Kirk-Othermer. Vol.11, 4th Ed. ('''1991''')</ref>

==Uses== AgF₂ is a strong fluorinating and oxidising agent. It is formed as an intermediate in the catalysis of gaseous reactions with fluorine by silver. With fluoride ions, it forms complex ions such as {{chem|AgF|3|-}}, the blue-violet {{chem|AgF|4|2-}}, and {{chem|AgF|6|4-}}.<ref name="wiberg_holleman">{{cite book | title = Inorganic chemistry | author1 = Egon Wiberg | author2 = Nils Wiberg | author3 = Arnold Frederick Holleman | publisher = Academic Press | year = 2001 | isbn = 0-12-352651-5 | pages = 1272–1273 }}</ref>

It is used in the fluorination and preparation of organic perfluorocompounds.<ref>{{cite journal |author1=Rausch, D. |author2=Davis, r. |author3=Osborne, D. W. | title = The Addition of Fluorine to Halogenated Olefins by Means of Metal Fluorides | journal = J. Org. Chem. | volume = 28 | pages = 494–497 | year = 1963 | doi = 10.1021/jo01037a055 | issue = 2}}</ref> 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): # CZ₃H + 2 AgF₂ → CZ₃F + HF + 2 AgF # CZ₃X + 2AgF₂ → CZ₃F + X₂ + 2 AgF # 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.

{{chem|AgF|2}} is also used in the fluorination of aromatic compounds, although selective monofluorinations are more difficult:<ref>{{cite journal |author1=Zweig, A. |author2=Fischer, R. G. |author3=Lancaster, J. | title = New Methods for Selective Monofluorination of Aromatics Using Silver Difluoride | journal = J. Org. Chem. | volume = 45 | year = 1980 | doi = 10.1021/jo01306a011 | pages = 3597 | issue = 18}}</ref>

:C₆H₆ + 2 AgF₂ → C₆H₅F + 2 AgF + HF

{{chem|AgF|2}} oxidises xenon to xenon difluoride in anhydrous HF solutions.<ref>{{cite journal |author1=Levec, J. |author2=Slivnik, J. |author3=Zemva, B. | title = On the Reaction Between Xenon and Fluorine | journal = Journal of Inorganic and Nuclear Chemistry | volume = 36 | year = 1974 | doi =10.1016/0022-1902(74)80203-4 | pages = 997 | issue = 5}}</ref>

:2 AgF₂ + Xe → 2 AgF + XeF₂

It also oxidises carbon monoxide to carbonyl fluoride.

:2 AgF₂ + CO → 2 AgF + COF₂

It reacts with water to form oxygen gas:{{citation needed|date=May 2010}}

:4 AgF₂ + 4 H₂O → 2 Ag₂O + 8 HF + O₂

{{chem|AgF|2}} can be used to selectively fluorinate pyridine at the ortho position under mild conditions.<ref>{{cite journal |author1=Fier, P. S. |author2=Hartwig, J. F. | title = Selective C-H Fluorination of Pyridines and Diazines Inspired by a Classic Amination Reaction | journal = Science | volume = 342 | year = 2013 |issue=6161 | doi =10.1126/science.1243759 | pages = 956–960 | pmid=24264986|bibcode=2013Sci...342..956F |s2cid=6584890 }}</ref>

==Safety== {{chem|AgF|2}} is a very strong oxidizer that reacts violently with water,<ref name="perry">{{cite book | title = Handbook of inorganic compounds | author1 = Dale L. Perry | author2 = Sidney L. Phillips | publisher = CRC Press | year = 1995 | isbn = 0-8493-8671-3 | page = 352 }}</ref> reacts with dilute acids to produce ozone, oxidizes iodide to iodine,<ref name="perry" /><ref name="armarego">{{cite book | title = Purification of Laboratory Chemicals | publisher = Butterworth-Heinemann | author1 = W. L. F. Armarego | author2 = Christina Li Lin Chai | edition = 6th | year = 2009 | isbn = 978-1-85617-567-8 | page = 490 }}</ref> and upon contact with acetylene forms the contact explosive silver acetylide.<ref name="pohanish">{{cite book | title = Wiley Guide to Chemical Incompatibilities | author1 = Richard P. Pohanish | author2 = Stanley A. Greene | edition = 3rd | publisher = John Wiley and Sons | year = 2009 | isbn = 978-0-470-38763-4 | page = 93 }}</ref> It is light-sensitive,<ref name="perry" /> very hygroscopic and corrosive. It decomposes violently on contact with hydrogen peroxide, releasing oxygen gas.<ref name="pohanish" /> It also liberates HF, {{chem|F|2}}, and elemental silver.<ref name="armarego" />

== References == {{Reflist}}

==External links== {{Commons category|Silver(II) fluoride}} * [https://web.archive.org/web/20060116134617/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] {{Webarchive|url=https://web.archive.org/web/20160303165537/http://www.chem.ox.ac.uk/inorganicchemistry3/Ag/AgF2.html |date=2016-03-03 }}

{{Silver compounds}} {{fluorides}}

{{DEFAULTSORT:Silver(Ii) Fluoride}} Category:Fluorides Category:Silver compounds Category:Metal halides Category:Fluorinating agents