Tetrabutylammonium hexafluorophosphate

Tetrabutylammonium hexafluorophosphate

Names
IUPAC name Tetrabutylammonium hexafluorophosphate
Other names 1-Butanaminium, N,N,N-tributyl-, hexafluorophosphate(1-)
Identifiers
CAS Number	3109-63-5
3D model (JSmol)	Interactive image
ChemSpider	144722
ECHA InfoCard	100.019.520
PubChem CID	165075
CompTox Dashboard (EPA)	DTXSID0074344
InChI InChI=1S/C16H36N.F6P/c1-5-9-13-17(14-10-6-2,15-11-7-3)16-12-8-4;1-7(2,3,4,5)6/h5-16H2,1-4H3;/q+1;-1 Key: BKBKEFQIOUYLBC-UHFFFAOYSA-N InChI=1/C16H36N.F6P/c1-5-9-13-17(14-10-6-2,15-11-7-3)16-12-8-4;1-7(2,3,4,5)6/h5-16H2,1-4H3;/q+1;-1 Key: BKBKEFQIOUYLBC-UHFFFAOYAC
SMILES CCCC[N+](CCCC)(CCCC)CCCC.F[P-](F)(F)(F)(F)F
Properties
Chemical formula	C16H36F6NP
Molar mass	387.4279 g·mol−1
Appearance	white powder
Melting point	244–246 °C (471–475 °F; 517–519 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Tetrabutylammonium hexafluorophosphate is a salt with the formula NBu₄PF₆. It is a white powder that is used as an electrolyte in nonaqueous electrochemistry. It is highly soluble in polar organic solvents such as acetone and acetonitrile.

The salt consists of a positively charged tetrabutylammonium, a quaternary ammonia cation and a weakly basic hexafluorophosphate anion. These species are chemically inert, which allows the salt to serve as an inert electrolyte over a wide potential range.

Preparation

This salt can be prepared by the reaction of tetrabutylammonium bromide and potassium hexafluorophosphate in aqueous solution. ^[1]

(C₄H₉)₄NBr + KPF₆ → (C₄H₉)₄NPF₆ + KBr

Given the sensitivity of electrochemical experiments, this salt is usually further purified, e.g., by recrystallization from aqueous or absolute ethanol. ^[2]

Use

This salt is used as a supporting electrolyte in electroanalysis as well as electrolytic growth methods (electrocrystallization). For instance, in the presence of this salt, the electrochemical oxidation of tetramethyltetraselenafulvalene (TMTSF) yields single crystals of (TMTSF)₂PF₆. This material is the first organic superconductor (T_c = 0.9 K at 12 kbar) reported by Klaus Bechgaard and Denis Jérome in 1980. ^[3]

References

1. Eliassaf, Jehudah; Fuoss, Raymond M.; Lind Jr., John E. (1963). "Conductance of Quaternary Ammonium Hexafluorophosphates in acetonitrile". The Journal of Physical Chemistry. 67 (9): 1941–1942. doi:10.1021/j100803a519.
2. Zoski, Cynthia G. (2007). Handbook of Electrochemistry (1st ed.). Amsterdam: Elsevier.
3. Jérome, D.; Mazaud, A.; Ribault, M.; Bechgaard, K. (1980). "Superconductivity in a synthetic organic conductor (TMTSF)₂PF₆". Journal de Physique Lettres. 41: 95–98. doi:10.1051/jphyslet:0198000410409500.