Silver(II) fluoride

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.

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.

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

For some time, it was doubted that silver was actually in the +2 oxidation state, rather than some combination of states such as AgI[AgIIIF4], which would be similar to silver(I,III) oxide. Neutron diffraction studies, however, confirmed its description as silver(II). The AgI[AgIIIF4] was found to be present at high temperatures, but it was unstable with respect to AgF2.

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.

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

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 , the blue-violet , and .{{cite book

It is used in the fluorination and preparation of organic perfluorocompounds. 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.

is also used in the fluorination of aromatic compounds, although selective monofluorinations are more difficult:

:C6H6 + 2 AgF2 → C6H5F + 2 AgF + HF

oxidises xenon to xenon difluoride in anhydrous HF solutions.

: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:

:4 AgF2 + 4 H2O → 2 Ag2O + 8 HF + O2

can be used to selectively fluorinate pyridine at the ortho position under mild conditions.

Safety

is a very strong oxidizer that reacts violently with water,{{cite book

References

References

1. Priest, H. F.. (1950). "Inorganic Syntheses".
2. ''Encyclopedia of Chemical Technology.'' Kirk-Othermer. Vol.11, 4th Ed. ('''1991''')
3. (1998). "Surface Characterization Study of AgF and AgF₂ Powders Using XPS and ISS". Applied Surface Science.
4. (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.]].
5. (1990-01-22). "Einkristalluntersuchungen an AgF 2". Zeitschrift für anorganische und allgemeine Chemie.
6. (1963). "The Addition of Fluorine to Halogenated Olefins by Means of Metal Fluorides". [[J. Org. Chem.]].
7. (1980). "New Methods for Selective Monofluorination of Aromatics Using Silver Difluoride". [[J. Org. Chem.]].
8. (1974). "On the Reaction Between Xenon and Fluorine". Journal of Inorganic and Nuclear Chemistry.
9. (2013). "Selective C-H Fluorination of Pyridines and Diazines Inspired by a Classic Amination Reaction". Science.