Silver hexafluorophosphate

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; 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: :AgPF6 + Re(CO)5Br + CH3CN → AgBr + [Re(CO)5(CH3CN)]PF6

Ligands with tightly-bound halide atoms coordinate the silver, but do not themselves decompose: :AgPF6 + 2 XeF2 → [Ag(XeF2)2]PF6.

AgPF6 can act as an oxidant, forming silver metal as a by-product. For example, in solution in dichloromethane, ferrocene is oxidised to ferrocenium hexafluorophosphate:

:AgPF6 + Fe(C5H5)2 → Ag + [Fe(C5H5)2]PF6 (E = 0.65 V)

Related reagents

In terms of their properties and applications, silver tetrafluoroborate (AgBF4) and the hexafluoroantimonate (AgSbF6) are similar to AgPF6.

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 AgPF6, 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.

References

References

1. Grochala, Wojciech. (Oct 2007). "Atypical compounds of gases, which have been called 'noble'". Royal Society of Chemistry.
2. (1996). "Chemical Redox Agents for Organometallic Chemistry". [[Chem. Rev.]].