TASF reagent

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TASF reagent
Skeletal formulas of the TASF reagent
Ball-and-stick models of the component ions of the TASF reagent
IUPAC name
Tris(dimethylamino)sulfonium difluorotrimethylsilicate
3D model (JSmol)
ECHA InfoCard 100.156.426
Molar mass 275.48
Appearance Colorless solid
Melting point 98 to 101 °C (208 to 214 °F; 371 to 374 K)
Except where otherwise noted, 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, p. 528