Tetramethylammonium fluoride

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Tetramethylammonium fluoride
Tetramethylammonium fluoride.svg
Preferred IUPAC name
N,N,N-Trimethylmethanaminium fluoride
3D model (JSmol)
ECHA InfoCard 100.006.154 Edit this at Wikidata
EC Number
  • 206-769-0
  • InChI=1S/C4H12N.FH/c1-5(2,3)4;/h1-4H3;1H/q+1;/p-1
  • C[N+](C)(C)C.[F-]
Molar mass 93.145 g·mol−1
Appearance white solid
GHS labelling:
GHS07: Exclamation mark
H302, H312, H315, H319, H332, H335
P261, P264, P270, P271, P280, P301+P312, P302+P352, P304+P312, P304+P340, P305+P351+P338, P312, P321, P322, P330, P332+P313, P337+P313, P362, P363, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Tetramethylammonium fluoride is the quaternary ammonium salt with the formula (CH3)4NF. This hygroscopic white 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. Historically, there has been two main approaches to prepare TMAF: (i) Via neutralization of tetramethylammonium hydroxide (TMAOH) with HF, and (ii) through the metathesis reaction of different ammonium salts with inorganic sources of fluoride, such as KF or CsF.[1] 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.[2]

Related salts[edit]

(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.[3] A more elaborate phosphazenium salt ([(CH3)2N)3P]2N+F) is also known.[4]


  1. ^ Iashin, Vladimir; Wirtanen, Tom; Perea-Buceta, Jesus E. (2022-02-18). "Tetramethylammonium Fluoride: Fundamental Properties and Applications in C-F Bond-Forming Reactions and as a Base". Catalysts. 12 (2): 233. doi:10.3390/catal12020233. ISSN 2073-4344.
  2. ^ 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 (21): 7619–7625. doi:10.1021/ja00177a025.{{cite journal}}: CS1 maint: uses authors parameter (link)
  3. ^ Kornath, Andreas; Neumann, F.; Oberhammer, H. (2003). "Tetramethylphosphonium Fluoride: "Naked" Fluoride and Phosphorane". Inorganic Chemistry. 42 (9): 2894–2901. doi:10.1021/ic020663c. PMID 12716181.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. ^ 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. ISBN 0471936235.
  5. ^ 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.