tetramethylammonium fluoride
{{Chembox
| ImageFile = Tetramethylammonium fluoride.svg
| ImageSize =
| ImageAlt =
| PIN = N,N,N-Trimethylmethanaminium fluoride
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|Section1={{Chembox Identifiers
| CASNo = 373-68-2
| PubChem = 67803
| EC_number = 206-769-0
| ChemSpiderID = 61120
| StdInChI=1S/C4H12N.FH/c1-5(2,3)4;/h1-4H3;1H/q+1;/p-1
| StdInChIKey = GTDKXDWWMOMSFL-UHFFFAOYSA-M
| SMILES = C[N+](C)(C)C.[F-]
}}
|Section2={{Chembox Properties
| C=4|H=12|N=1|F=1
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| Appearance = white solid
| Density =
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|Section3={{Chembox Hazards
| GHSPictograms = {{GHS07}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|302|312|315|319|332|335}}
| PPhrases = {{P-phrases|261|264|270|271|280|301+312|302+352|304+312|304+340|305+351+338|312|321|322|330|332+313|337+313|362|363|403+233|405|501}}
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Tetramethylammonium fluoride, commonly abbreviated TMAF, is the quaternary ammonium salt with the formula (CH3)4NF. This hygroscopic white solid is a source of “naked fluoride": fluoride ions not complexed with a metal atom. Most other soluble salts of fluoride are in fact bifluorides, HF2–. Historically, there have been two main approaches to prepare tetramethylammonium fluoride: hydrofluoric acid neutralization of tetramethylammonium hydroxide, and salt metathesis between different ammonium salts and inorganic fluoride sources, such as KF or CsF.{{Cite journal|last1=Iashin|first1=Vladimir|last2=Wirtanen|first2=Tom|last3=Perea-Buceta|first3=Jesus E.|date=2022-02-18|title=Tetramethylammonium Fluoride: Fundamental Properties and Applications in C-F Bond-Forming Reactions and as a Base|journal=Catalysts|language=en|volume=12|issue=2|pages=233|doi=10.3390/catal12020233|issn=2073-4344|doi-access=free|hdl=10138/340938|hdl-access=free}} Because the fluoride anion is extremely basic, the salt slowly reacts with acetonitrile, inducing dimerization to CH3C(NH2)=CHCN, which co-crystallizes.{{cite journal|author1=Christe, K. O. |author2=Wilson, W. W. |author3=Wilson, R. D. |author4=Bau, R. |author5=Feng, J. A. |title=Syntheses, Properties, and Structures of Anhydrous Tetramethylammonium Fluoride and Its 1:1 Adduct with trans-3-Amino-2-butenenitrile|journal=Journal of the American Chemical Society|year=1990|volume=112|issue=21|pages=7619–7625|doi=10.1021/ja00177a025|bibcode=1990JAChS.112.7619C }}
Related salts
- Tetramethylphosphonium fluoride (CH3)4PF forms stable acetonitrile solutions. It is prepared from the ylide and potassium bifluoride:
:(CH3)3P=CH2 + KHF2 → (CH3)4PF + KF
:Gaseous tetramethylphosphonium fluoride exists as the phosphorane but autoionizes in acetonitrile solution.{{cite journal|title=Tetramethylphosphonium Fluoride: "Naked" Fluoride and Phosphorane|author=Kornath, Andreas; Neumann, F.; Oberhammer, H.|journal=Inorganic Chemistry|year=2003|volume=42|issue=9|pages=2894–2901|doi=10.1021/ic020663c|pmid=12716181}} A more elaborate phosphazenium salt ([(CH3)2N)3P]2N+F−) is also known.{{cite encyclopedia|author=Schwesinger, Reinhard|title=1,1,1,3,3,3-Hexakis(dimethylamino)-1λ5,3λ5-diphosphazenium Fluoride|encyclopedia=e-EROS Encyclopedia of Reagents for Organic Synthesis|year=2001|pages=1–2|doi=10.1002/047084289X.rh014m|isbn=0471936235}}
- Anhydrous Tetrabutylammonium fluoride has been prepared by the reaction of hexafluorobenzene and tetrabutylammonium cyanide.{{cite journal |author1=Haoran Sun |author2=Stephen G. DiMagno |name-list-style=amp | title= Anhydrous Tetrabutylammonium Fluoride | journal= Journal of the American Chemical Society | year= 2005 | volume= 127 | pages= 2050–1| doi=10.1021/ja0440497 | pmid= 15713075 | issue= 7|bibcode=2005JAChS.127.2050S }}