Dithiolium salt

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. For example, the 1,2-ditholium ring can be represented as an allyl cation of the three carbons, with each sulfur atom donating one of its lone pairs of electrons to give a total of three pairs.



Preparation, occurrence, reactions
1,2-Dithiolium cations have been prepared from 1,3-diketones by treatment with H2S and oxidants such as bromine.
 * (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)2S2CE + R'+   ->    [(RC)2S2CER']+

The analogous reaction of electrophiles with 1,2-dithiole-2-ones affords 1,2-dithiolium cations.