TASF reagent

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TASF reagent
CAS number 59218-87-0 N
PubChem 9795567
ChemSpider 7971333 YesY
Jmol-3D images Image 1
Molecular formula C9H27F2N3SSi
Molar mass 275.48 g mol−1
Appearance Colorless solid
Melting point 98 to 101 °C (208 to 214 °F; 371 to 374 K)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

The TASF reagent or tris(dimethylamino)sulfonium difluorotrimethylsilicate is a reagent in organic chemistry with structural formula [((CH3)2N)3S]+[F2Si(CH3)3]. It is an anhydrous source of fluoride and is used to cleave silyl ether protective groups. Many other fluoride reagents are known, but few are truly anhydrous, because of the extraordinary basicity of "naked" F. In TASF, the fluoride is masked as an adduct with the weak Lewis acid trimethylsilylfluoride (FSi(CH3)3). The sulfonium cation ((CH3)2N)3S+ is unusually non-electrophilic due to the electron-donating properties of the three (CH3)2N substituents.

This compound is prepared from sulfur tetrafluoride:

3 (CH3)2NSi(CH3)3 + SF4 → 2 (CH3)3SiF + [((CH3)2N)3S]+[F2Si(CH3)3]

The colorless salt precipitates from the reaction solvent, diethyl ether.[1]


  1. ^ W. J. Middleton (1990), "Tris(dimethylamino)sulfonium difluorotrimethylsilicate", Org. Synth. ; Coll. Vol. 7: 528