Ferrocenium hexafluorophosphate

Ferrocenium hexafluorophosphate is an organometallic compound with the formula [Fe(C₅H₅)₂]PF₆. This salt is composed of the cation [Fe(C₅H₅)₂]⁺ and the hexafluorophosphate anion (PF⁻
₆). The related tetrafluoroborate is also a popular reagent with similar properties. The ferrocenium cation is often abbreviated Fc⁺ or Cp₂Fe⁺. The salt is deep blue in color and paramagnetic.

Ferrocenium hexafluorophosphate

Names
IUPAC name Ferrocenium hexafluorophosphate
Identifiers
CAS Number	11077-24-0[1]
3D model (JSmol)	Interactive image
ChemSpider	17340319
ECHA InfoCard	100.157.410
PubChem CID	16212479
InChI InChI=1S/2C5H5.F6P.Fe/c2*1-2-4-5-3-1;1-7(2,3,4,5)6;/h2*1-5H;;/q;;-1; Key: PCJFEGIXYOQEQD-UHFFFAOYSA-N
SMILES [CH-]1C=CC=C1.[Fe+3].[CH-]1C=CC=C1.F[P-](F)(F)(F)(F)F
Properties
Chemical formula	C10H10F6FeP
Molar mass	330.999 g·mol−1
Appearance	dark blue powder
Density	1.808 g/cm3
Melting point	(decomposes)
Solubility in acetonitrile	Soluble[citation needed]
Structure
Crystal structure	monoclinic
Space group	P21/c
Lattice constant	a = 13.429(3) Å, b = 9.547(2) Å, c = 9.547(2) Å α = 90°, β = 93.31(3)°, γ = 90°[2]
Lattice volume (V)	1215.8(5) Å3
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P261, P305+P351+P338
Safety data sheet (SDS)	External MSDS
Related compounds
Other anions	Ferrocenium tetrafluoroborate
Related compounds	Ferrocene
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Ferrocenium salts are one-electron oxidizing agents, and the reduced product, ferrocene, is relatively inert and readily separated from ionic products. The ferrocene–ferrocenium couple is often used as a reference in electrochemistry. In acetonitrile solution that is 0.1 M in NBu₄PF₆, the Fc⁺/Fc couple is +0.641 V with respect to the normal hydrogen electrode.^[3]

Preparation and structure

Commercially available, this compound may be prepared by oxidizing ferrocene with ferric salts followed by addition of hexafluorophosphoric acid.^[3]

The compound is monoclinic with well-separated cation and anion; the PF⁻
₆ may rotate freely. The average Fe-C bond length is 2.047 Å, which is virtually indistinguishable from the Fe-C distance in ferrocene.^[2]