Tetramethylammonium fluoride

Tetramethylammonium fluoride
Names
	IUPAC name tetramethylazanium;fluoride
Identifiers
CAS Number	373-68-2;
3D model (JSmol)	Interactive image;
ChemSpider	61120;
EC Number	206-769-0
PubChem CID	67803;
	InChI InChI=1S/C4H12N.FH/c1-5(2,3)4;/h1-4H3;1H/q+1;/p-1 Key: GTDKXDWWMOMSFL-UHFFFAOYSA-M;
	SMILES C[N+](C)(C)C.[F-];
Properties
Chemical formula	C4H12FN
Molar mass	93.15 g·mol−1
Appearance	white solid
Hazards
GHS pictograms
GHS signal word	Warning
GHS hazard statements	H302, H312, H315, H319, H332, H335
GHS precautionary statements	P261, P264, P270, P271, P280, P301+312, P302+352, P304+312, P304+340, P305+351+338, P312, P321, P322, P330, P332+313, P337+313, P362, P363, P403+233, P405, P501
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
	Infobox references

Tetramethylammonium fluoride is the quaternary ammonium salt with the formula (CH₃)₄NF. This colorless solid is a source of “naked fluoride", that is fluoride ions not connected to a metal atom in a complex. Most other soluble salts of fluoride are in fact bifluorides, HF₂^–. Tetramethylammonium fluoride is produced by combining tetramethylammonium hydroxide and hydrogen fluoride in isopropanol. Due to the high basicity of the fluoride anion, the salt reacts slowly with acetonitrile, inducing its dimerization to CH₃C(NH₂)=CHCN, which co-crystallizes.^[1]

Related salts

Tetramethylphosphonium fluoride (CH₃)₄PF forms stable solutions in acetonitrile. It is prepared by reaction of the ylide with potassium bifluoride:

(CH₃)₃P=CH₂ + KHF₂ → (CH₃)₄PF + KF

In the gas phase, tetramethylphosphonium fluoride exists as the phosphorane, but in acetonitrile solution, it dissociates into ions.^[2]

A more elaborate phosphazenium salt ([(CH₃)₂N)₃P]₂N⁺F⁻) is also known.^[3]
Tetrabutylammonium fluoride has been prepared by the reaction of hexafluorobenzene and tetrabutylammonium cyanide. This salt was once suspected of being unstable owing to Hofmann degradation.^[4]

References

↑ Christe, K. O.; Wilson, W. W.; Wilson, R. D.; Bau, R.; Feng, J. A. (1990). "Syntheses, Properties, and Structures of Anhydrous Tetramethylammonium Fluoride and Its 1:1 Adduct with trans-3-Amino-2-butenenitrile". Journal of the American Chemical Society. 112: 7619–7625. doi:10.1021/ja00177a025.
↑ Kornath, Andreas; Neumann, F.; Oberhammer, H. (2003). "Tetramethylphosphonium Fluoride: "Naked" Fluoride and Phosphorane". Inorganic Chemistry. 42: 2894–2901. doi:10.1021/ic020663c.
↑ Schwesinger, Reinhard (2001). "1,1,1,3,3,3-Hexakis(dimethylamino)-1λ5,3λ5-diphosphazenium Fluoride". e-EROS Encyclopedia of Reagents for Organic Synthesis. pp. 1–2. doi:10.1002/047084289X.rh014m.
↑ Haoran Sun & Stephen G. DiMagno (2005). "Anhydrous Tetrabutylammonium Fluoride". Journal of the American Chemical Society. 127 (7): 2050–1. doi:10.1021/ja0440497. PMID 15713075.

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[1] Christe, K. O.; Wilson, W. W.; Wilson, R. D.; Bau, R.; Feng, J. A. (1990). "Syntheses, Properties, and Structures of Anhydrous Tetramethylammonium Fluoride and Its 1:1 Adduct with trans-3-Amino-2-butenenitrile". Journal of the American Chemical Society. 112: 7619–7625. doi:10.1021/ja00177a025.

[2] Kornath, Andreas; Neumann, F.; Oberhammer, H. (2003). "Tetramethylphosphonium Fluoride: "Naked" Fluoride and Phosphorane". Inorganic Chemistry. 42: 2894–2901. doi:10.1021/ic020663c.

[3] Schwesinger, Reinhard (2001). "1,1,1,3,3,3-Hexakis(dimethylamino)-1λ5,3λ5-diphosphazenium Fluoride". e-EROS Encyclopedia of Reagents for Organic Synthesis. pp. 1–2. doi:10.1002/047084289X.rh014m.

[dimagno-4] Haoran Sun & Stephen G. DiMagno (2005). "Anhydrous Tetrabutylammonium Fluoride". Journal of the American Chemical Society. 127 (7): 2050–1. doi:10.1021/ja0440497. PMID 15713075.