TASF reagent

TASF reagent
Names
	Preferred IUPAC name 2-(Dimethylamino)-1,1,3,3-tetramethyldiazathian-2-ium difluorotri(methyl)silanuide
Identifiers
CAS Number	59218-87-0 ;
3D model (JSmol)	Interactive image;
ChemSpider	7971333 ;
ECHA InfoCard	100.156.426
PubChem CID	9795567;
CompTox Dashboard (EPA)	DTXSID50430833 ;
	InChI InChI=1S/C6H18N3S.C3H9F2Si/c1-7(2)10(8(3)4)9(5)6;1-6(2,3,4)5/h1-6H3;1-3H3/q+1;-1 Key: JMGVTLYEFSBAGJ-UHFFFAOYSA-N ; InChI=1/C6H18N3S.C3H9F2Si/c1-7(2)10(8(3)4)9(5)6;1-6(2,3,4)5/h1-6H3;1-3H3/q+1;-1 Key: JMGVTLYEFSBAGJ-UHFFFAOYAE;
	SMILES F[Si-](F)(C)(C)C.N([S+](N(C)C)N(C)C)(C)C;
Properties
Chemical formula	C9H27F2N3SSi
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). verify (what is ?) 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]

Structure

The cation [((CH₃)₂N)₃S]⁺ is a sulfonium ion. The S-N distances are 1.612 and 1.675 pm. The N-S-N angles are 99.6°. The anion is [F₂Si(CH₃)₃]⁻. It is trigonal bipyramidal with mutually trans fluorides. The Si-F distances are 176 picometers. The Si-C distances are 188 pm.^[2]

References

^ W. J. Middleton (1990). "Tris(dimethylamino)sulfonium difluorotrimethylsilicate". Organic Syntheses; Collected Volumes, vol. 7, p. 528.
^ Dixon, David A.; Farnham, William B.; Heilemann, W.; Mews, R.; Noltemeyer, M. (1993). "Structural studies of tris(dialkylamino) sulfonium (TAS) fluorosilicates". Heteroatom Chemistry. 4 (2–3): 287–295. doi:10.1002/hc.520040225.

[1] W. J. Middleton (1990). "Tris(dimethylamino)sulfonium difluorotrimethylsilicate". Organic Syntheses; Collected Volumes, vol. 7, p. 528.

[2] Dixon, David A.; Farnham, William B.; Heilemann, W.; Mews, R.; Noltemeyer, M. (1993). "Structural studies of tris(dialkylamino) sulfonium (TAS) fluorosilicates". Heteroatom Chemistry. 4 (2–3): 287–295. doi:10.1002/hc.520040225.

[1]

[2]