Tetrabutylammonium hexafluorophosphate

Chemical Properties

Tetrabutylammonium hexafluorophosphate is a white powder, extremely soluble in polar organic solvents such as acetone and acetonitrile.

Uses

Tetrabutylammonium hexafluorophosphate can be used as a supporting electrolyte for the formation of cyclic disulfide moiety of 3,5-diimido-1,2-dithiolane derivatives by S-S coupling of dithioanilides.

Uses

Tetrabutylammonium hexafluorophosphate (TBAPF₆) or TBAHP can be used:

• As the supporting electrolyte in cyclic voltammetric studies.
• As a reactant in the synthesis of fluorescent nanofibrous sensing films for detecting nitro-explosive vapors.

General Description

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Hazard

Tetrabutylammonium hexafluorophosphate is harmful to humans and is an eye and skin irritant. It may cause severe eye irritation. It may also cause respiratory irritation. Harmful if ingested.

Synthesis

The general procedure for the synthesis of tetrabutylammonium hexafluorophosphate from tetrabutylammonium bromide was as follows: potassium hexafluorophosphate (K[PF6], 2.055 g, 11.2 mmol) was dissolved in 30 mL of deionized water. Tetrabutylammonium bromide ([(n-Bu4)N]Br, 3.601 g, 11.2 mmol) was dissolved in 30 mL of dichloromethane (CH2Cl2) and the resulting solution was subsequently added to the aqueous potassium hexafluorophosphate solution. After stirring the reaction mixture for 24 h at room temperature, phase separation was carried out. The organic phase was washed three times with 10 mL of deionized water, followed by drying with anhydrous sodium carbonate (Na2CO3) and filtration. The filtrate was concentrated by rotary evaporation to give a white solid product. The resulting solid was dried under vacuum at 80 °C for 18 h to give 3.822 g of tetrabutylammonium hexafluorophosphate ([(n-Bu4)N][PF6]) in 88% yield (9.87 mmol). The product characterization data are as follows: differential scanning calorimetry (DSC, 10 K/min): melting point (m.p.) = 250 °C, decomposition temperature (Tdec) = 388 °C. Calculated elemental analysis (measured values): C 49.60% (49.97%), H 9.37% (9.00%), N 3.61% (3.61%).1H NMR (25 °C, CD3CN, 300.13 MHz, δ ppm): 0.96 (t, 12H, CH3), 1.34 (m, 8H, CH3-CH2), 1.59 (m , 8H, CH2-CH2N), 3.06 (m, 8H, NCH2).19F NMR (25 °C, CD3CN, 300.13 MHz, δ ppm): -73.0 (d, 6F, PF6, JP-F = 706.7 Hz).31P NMR (25 °C, CD3CN, 300.13 MHz, δ ppm): - 144.6 (sept, 1P, PF6, JP-F = 706.7 Hz). Infrared spectrum (ATR, 32 scans, ν cm-1): 2966 (m), 2937 (w), 2879 (w), 1472 (m), 1404 (w), 1386 (w), 1360 (w), 1350 (w), 1319 (w), 1260 (w), 1242 (w), 1165 (w), 1109 (w), 1070 (w), 1035 (w), 931 (w), 880 (m), 829 (s), 738 (m), 555 (s).

Purification Methods

Recrystallise it from saturated EtOH/water and dry it for 10hours in a vacuum at 70o. Also recrystallise it three times from absolute EtOH and dry it for 2 days in a drying pistol under a vacuum at boiling toluene temperature [Bedard & Dahl J Am Chem Soc 108 5933 1986]. It is a stable supporting electrolyte in organic solvents [Baiser in Organic Electrochemitry M. Dekker NY p228 1973.]

References

[1] European Journal of Organic Chemistry, 2012, # 19, p. 3566 - 3569
[2] Patent: WO2014/167034, 2014, A2. Location in patent: Page/Page column 48; 49
[3] Angewandte Chemie - International Edition, 2015, vol. 54, # 15, p. 4474 - 4477
[4] Angew. Chem., 2015, vol. 127, # 15, p. 4556 - 4559,4
[5] Chemistry - A European Journal, 2016, vol. 22, # 12, p. 4175 - 4188