Potassium Hexafluorophosphate


[17084-13-8]  · F6KP  · Potassium Hexafluorophosphate  · (MW 184.07)

(production of diaryliodonium and alkylaryliodonium hexafluorophosphates and triarylsulfonium hexafluorophosphates used as photoinitiators for cationic polymerization; used for the preparation of organic hexafluorophosphates; used to produce catalysts for peptide coupling reactions)

Physical Data: mp 575 °C; d 2.55 g cm-3.

Solubility: sol water (9.3 g/100 ml at 25 °C and 20.6 at 50 °C), sol diglyme (40 g/100 ml at 25 °C).

Form Supplied in: white powder; commercially available.

Analysis of Reagent Purity: volumetric method for determination of total fluoride;1,2 ion selective electrode for determination of soluble fluoride (KF) impurity;3 gravimetric method of analysis for determination of PF6 by using tetraphenylarsonium chloride.4

Handling, Storage, and Precautions: stable at ambient temperature. This material can be stored in polyethylene, Teflon® or metal containers. The OSHA permissible exposure limit5 and American Conference of Governmental Industrial Hygienists (ACGIH) established Threshold Limit Value6 (TLV) as a time-weighted average for fluorides is 2.5 mg (as fluoride) per cubic meter of air.

Diaryliodonium Hexafluorophosphates.

Diaryliodonium hexafluorophosphates are prepared by the metathesis reaction of diaryliodonium bisulfates and potassium hexafluorophosphate. There are many methods reported in the literature for the synthesis of diaryliodonium bisulfates.7-10 Aromatic substrates bearing electron-withdrawing groups such as NO2, halogens, CO2H, or MeSO2 are best coupled by the method used by Masson and co-workers7 employing iodyl sulfate to produce symmetrical diaryliodonium bisulfate (eq 1).

Diaryliodonium bisulfates having electron-donating groups on the aromatic ring are readily prepared by the direct coupling of their aromatic precursor compounds using an alkali iodate in a mixture of acetic acid, acetic anhydride, and sulfuric acid (eq 2).8,9

Unsymmetrical iodonium bisulfates can be prepared by the direct coupling of an aromatic compound with an iodoso compound in the presence of a strong protonic acid (eq 3).10

Diaryliodonium hexafluorophosphates are efficient photoinitiators for the cationic polymerization of a variety of monomers (eqs 4-6). The 4,4-dimethyldiphenyliodonium hexafluorophosphate, bis(4-t-butylphenyliodonium) hexafluorophosphate, and diphenyliodonium hexafluorophosphate can be prepared by using Crivello and Lam's method.11-13

Diphenyliodium hexafluorophosphate is used in copper(I or II) catalyzed polymerization (eq 7).14

Diaryliodium hexafluorophosphates are used to prepare trialkylsulfonium hexafluorophosphate (eqs 8 and 9).15,16

Diaryliodium hexafluorophosphates are also used in polymerization, where ring opening of the monomer takes place (eq 10).17

Triarylsulfonium Hexafluorophosphates.

To a solution of 21.5 g (0.05 mol) of tris(3,5-dimethyl-4-hydroxyphenyl)sulfonium chloride in hot ethanol was added 9.2 g (0.05 mol) of potassium hexafluorophosphate. About 100 mL of water was added and crystallization of the sulfonium hexafluorophosphate took place. The salt was filtered, washed thoroughly with water, then with ether, and dried (eqs 11 and 12).

Triarylsulfonium hexafluorophosphates are used in photoinitiated cationic polymerization (eqs 13-15).18

Peptide Coupling Reaction.

Potassium hexafluorophosphate is used to produce azidotris(dialkylamino)phosphonium salts as reagents for peptide coupling (eqs 16 and 17).19

1. Cady, G. H. Anal. Chem. 1976, 48, 655.
2. Willard, H. H.; Winter, O. B. Ind. Eng. Chem., Anal. Ed. 1933, 5, 7.
3. Analytical Procedures for Fluoride Analyses; Orion Research: Boston, MA, 1993.
4. Affsprung, H. E.; Archer, V. S. Anal. Chem. 1963, 35, 1912.
5. Code of Federal Regulations 29, Part 1910.1000.
6. Threshold Limit Values for Chemical Substances and Physical Agents, 1993-1994. The American Conference of Governmental Industrial Hygienists: Cincinnati, OH.
7. Masson, I. Nature 1957, 139, 150. Masson, I.; Race, E. JCS 1937, 1718; Masson, I.; Hamby, W. E. JCS 1937, 1699; Masson, I.; Arugurment, C. JCS 1938, 1702.
8. Berry, D. A.; et al. 12th IUPAC Congress, New York, Sept. 1980; Abstr. p 486.
9. Beringer, F. M.; Falk, R. A.; Karniol, M.; Lillien, I.; Masullo, G.; Mausner, M.; Sommer, E. JACS 1959, 81, 342.
10. Beringer, F. M.; Bachofner, H. E.; Falk, R. A.; Leff, M. JACS 1958, 80, 4279.
11. Crivello, J. V.; Lam, J. H. W. J. Polym. Sci., Polym. Symp. 1976, 56, 383.
12. Crivello, J. V.; Lam, J. H. W. Macromolecules 1977, 10, 1307.
13. Crivello, J. V.; Lam, J. H. W. JOC 1978, 43, 3055.
14. Crivello, J. V.; et al. U.S. Patent 4 450 360, 1984.
15. Crivello, J. V.; Lockhart, T. P.; Lee, J. E. J. Polym. Sci., Polym. Chem. Ed. 1983, 21, 97.
16. Crivello, J. V.; Lam, J. H. W. SC 1979, 9, 151.
17. Crivello, J. V. Chemtech. 1980, 624.
18. Crivello, J. V.; Lam, J. H. W. J. Polym. Sci., Polym. Chem. Ed. 1979, 17, 977.
19. Castro, B.; Dormoy, J. R. Fr. Patent 2 234 310, 1975.

Tariq Mahmood

Ozark-Mahoning Company, Tulsa, OK, USA

Copyright 1995-2000 by John Wiley & Sons, Ltd. All rights reserved.