TASF reagent
IUPAC name	Tris(dimethylamino)sulfonium difluorotrimethylsilicate
Identifiers
CAS number	59218-87-0
SMILES	C\[N](C)=S(N(C)C)/N(C)C.C[Si](C)(C)(F)F
Properties
Molecular formula	C9H27F2N3SSi
Molar mass	275.48 g mol−1
Appearance	Colorless solid
Melting point	98-101 °C
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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]

[edit] References

1. ^ W. J. Middleton (1990), "Tris(dimethylamino)sulfonium difluorotrimethylsilicate", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv7p0528 ; Coll. Vol. 7: 528