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Silver(II) fluoride
IUPAC name	silver(II) fluoride
Other names	silver difluoride
Identifiers
CAS number	7775-41-9
Properties
Molecular formula	AgF2
Molar mass	145.865 g/mol
Appearance	white or grey crystalline powder, hygroscopic
Density	4.58 g/cm3
Melting point	690 °C (963 K)
Boiling point	decomposes at 700 °C (973 K)
Solubility in water	Decomposes, violently
Structure
Crystal structure	orthorhombic
Coordination; geometry	tetragonally elongated; octahedral coordination
Molecular shape	linear
Hazards
MSDS	MSDS
Main hazards	toxic, reacts violently; with water, powerful oxidizer
Related compounds
Other anions	silver(I,III) oxide
Other cations	copper(II) fluoride, palladium(II) fluoride, cadmium(II) fluoride
Related compounds	silver(I) fluoride
	Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
	Infobox references

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.

[edit] 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.^[1]^[2]

As a strong fluorinating agent, AgF₂ should be stored in Teflon or a passivated metal container. 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.

[edit] 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. ^[3]

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.^[4]

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).

[edit] Uses

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

Fluoronation and preparation of organic perfluorocompounds ^[5]

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) 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:^[6]

C₆H₆ + 2 AgF₂ → C₆H₅F + 2 AgF + HF

Oxidation of xenon ^[7]. This reaction, which can be explosive, proceeds in anhydrous HF solutions producing XeF₂.

AgF₂ oxidizes carbon monoxide to carbonyl fluoride.

[edit] References

^ Priest, H. F.; Swinehert, Carl F. (1950). "Anhydrous Metal Fluorides". Inorg. Synth. 3: 171–183. doi:10.1002/9780470132340.ch47.
^ Encyclopedia of Chemical Technology. Kirk-Othermer. Vol.11, 4th Ed. (1991)
^ J.T. Wolan, G.B. Hoflund (1998). "Surface Characterization Study of AgF and AgF₂ Powders Using XPS and ISS". Applied Surface Science 125: 251. doi:10.1016/S0169-4332(97)00498-4.
^ Hans-Christian Miller, Axel Schultz, and Magdolna Hargittai (2005). "Structure and Bonding in Silver Halides. A Quantum Chemical Study of the Monomers: Ag2X, AgX, AgX2, and AgX3(X = F, Cl, Br, I)". J. Am. Chem. Soc. 127 (22): 8133. doi:10.1021/ja051442j.
^ Rausch, D.; Davis, r.; Osborne, D. W. (1962). "The Addition of Fluorine to Halogenated Olefins by Means of Metal Fluorides". J. Org. Chem. 28: 494–497. doi:10.1021/jo01037a055.
^ Zweig, A.; Fischer, R. G.; Lancaster, J. (1980). "New Methods for Selective Monofluorination of Aromatics Using Silver Difluoride". J. Org. Chem. 45: 3597. doi:10.1021/jo01306a011.
^ Levec, J.; Slivnik, J.; Zemva, B. (1974). "On the Reaction Between Xenon and Fluorine". Journal of Inorganic Nuclear Chemistry 36: 997. doi:10.1016/0022-1902(74)80203-4.

[edit] External links

[0] Priest, H. F.; Swinehert, Carl F. (1950). "Anhydrous Metal Fluorides". Inorg. Synth. 3: 171–183. doi:10.1002/9780470132340.ch47.

[1] Encyclopedia of Chemical Technology. Kirk-Othermer. Vol.11, 4th Ed. (1991)

[2] J.T. Wolan, G.B. Hoflund (1998). "Surface Characterization Study of AgF and AgF₂ Powders Using XPS and ISS". Applied Surface Science 125: 251. doi:10.1016/S0169-4332(97)00498-4.

[3] Hans-Christian Miller, Axel Schultz, and Magdolna Hargittai (2005). "Structure and Bonding in Silver Halides. A Quantum Chemical Study of the Monomers: Ag2X, AgX, AgX2, and AgX3(X = F, Cl, Br, I)". J. Am. Chem. Soc. 127 (22): 8133. doi:10.1021/ja051442j.

[4] Rausch, D.; Davis, r.; Osborne, D. W. (1962). "The Addition of Fluorine to Halogenated Olefins by Means of Metal Fluorides". J. Org. Chem. 28: 494–497. doi:10.1021/jo01037a055.

[5] Zweig, A.; Fischer, R. G.; Lancaster, J. (1980). "New Methods for Selective Monofluorination of Aromatics Using Silver Difluoride". J. Org. Chem. 45: 3597. doi:10.1021/jo01306a011.

[6] Levec, J.; Slivnik, J.; Zemva, B. (1974). "On the Reaction Between Xenon and Fluorine". Journal of Inorganic Nuclear Chemistry 36: 997. doi:10.1016/0022-1902(74)80203-4.

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Contents

[edit] Preparation

[edit] Composition and structure

[edit] Uses

[edit] References

[edit] External links