Silver(II) fluoride

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.

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.

For some time, it was doubted silver was actually in the 2+ oxidation state rather in some combination of states such as AgI[AgIIIF4], which would be similar to silver 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.

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.

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):
 * Fluoronation and preparation of organic perfluorocompounds
 * 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:
 * C6H6 +  2 AgF2  →  C6H5F  +  2 AgF  +  HF


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


 * AgF2 oxidizes carbon monoxide to carbonyl fluoride.