Dithiolium salt
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Dithiolium salts are compounds of the formula [(RC)3S2]+X− (R = H, alkyl, aryl, etc.). These salts consist of a planar organic cation with a variety of anions such as halides. The five-membered ring cations are observed in either of two isomers, 1,2- and 1,3-dithiolium cations. These cations differ with respect to the relative positions of the pair of sulfur atoms. Both isomers feature a planar ring, which is aromatic owing to the presence of 6π electrons.[1] For example, the 1,2-ditholium ring can be represented as an allyl cation of the three carbons,[2] with each sulfur atom donating one of its lone pairs of electrons to give a total of three pairs.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/f0/KUXSEB.png/220px-KUXSEB.png)
Preparation, occurrence, reactions
1,2-Dithiolium cations are typically prepared from 1,3-diketones by treatment with H2S and oxidants such as bromine.[2]
- (RCO)2CH2 + 2 H2S + Br2 → [(RC)3S2]+Br− + 2 H2O + HBr
1,3-Dithiolium cations are often prepared by alkylation of the corresponding unsaturated dithio- or trithiocarbonates:
- [(RC)2S2C=E] + R+ → [(RC)2S2CER]+
The analogous reaction of electrophiles with 1,2-dithiole-2-ones affords 1,2-dithiolium cations.
The oxidation of tetrathiafulvalenes gives cations that exhibit the character of 1,3-dithiolium cations.
References
- ^ "The 1,2- and 1,3-Dithiolium Ions". Advances in Heterocyclic Chemistry. 27: 151–239. 1981. doi:10.1016/S0065-2725(08)60997-6.
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(help) - ^ a b "Improved synthesis of alkyl substituted 1,2-dithiolium salts". Journal of Organic Chemistry. 38: 2548–9. 1973. doi:10.1021/jo00954a028.
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(help) - ^ "3,5-Diphenyl-1,2-dithiolium-hydrogensulfat—Bildung und Struktur" [3.5-Diphenyl-l,2-dithiolium Hydrogensulphate—Synthesis and Structure]. Z. Naturforsch. B (in German). 47 (11): 1501–1504. 1992. doi:10.1515/znb-1992-1102.
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