Silver hexafluorophosphate
# Silver hexafluorophosphate

Silver hexafluorophosphate, sometimes referred to "silver PF-6," is an inorganic compound with the chemical formula $AgPF_6.$

## Uses and reactions

Silver hexafluorophosphate is a commonly encountered reagent in inorganic and organometallic chemistry. It is commonly used to replace halide ligands with the weakly coordinating hexafluorophosphate anion; the abstraction of the halide is driven by the precipitation of the appropriate silver halide.

Illustrative is the preparation of acetonitrile complexes from a metal bromide, a reaction that would typically be conducted in a solution of acetonitrile:

    $AgPF_6$ + $Re(CO)_5Br$ + $CH_3CN$ → AgBr + $[Re(CO)_5(CH_3CN)]PF_6$

$AgPF_6$ can act as an oxidant, forming silver metal as a by-product. For example, in solution in dichloromethane, ferrocene is oxidised to ferrocenium hexafluorophosphate:

    $AgPF_6$ + $Fe(C_5H_5)_2$ → Ag + $[Fe(C_5H_5)_2]PF_6$ (E = 0.65 V)

## Related reagents

In terms of their properties and applications, silver tetrafluoroborate $(AgBF_4)$ and the hexafluoroantimonate $(AgSbF_6)$ are similar to $AgPF_6.$

### Comparison with silver nitrate

Silver nitrate is a traditional and less expensive halide abstraction reagent, as indicated by its widespread use in qualitative tests for halides.

Relative to $AgPF_6,$ however, silver nitrate is poorly soluble in weakly basic solvents: the nitrate anion is Lewis basic and presents an interfering ligand that precludes its use in stringent applications.

