Benzene-1,2-dithiol
# Benzene-1,2-dithiol

Benzene-1,2-dithiol is the organosulfur compound with the formula $C_6H_4(SH)_2.$ This colourless viscous liquid consists of a benzene ring with a pair of adjacent thiol groups. The conjugate base of this diprotic compound serves as chelating agent in coordination chemistry and a building block for the synthesis of other organosulfur compounds.

## Synthesis

The compound is prepared by ortho-lithiation of benzenethiol using butyl lithium (BuLi) followed by sulfidation:

    $C_6H_5SH$ + 2 BuLi → $C_6H_4SLi-2-Li$ + 2 BuH
    $C_6H_4SLi-2-Li$ + S → $C_6H_4(SLi)_2$
    $C_6H_4(SLi)_2$ + 2 HCl → $C_6H_4(SH)_2$ + 2 LiCl

The compound was first prepared from 2-aminobenzenethiol via diazotization. Alternatively, it forms from 1,2-dibromobenzene.

## Reactions

Oxidation mainly affords the polymeric disulfide. Reaction with metal dihalides and metal oxides gives the dithiolate complexes of the formula $L_nM(S_2C_6H_4)$ where $L_nM$ represents a variety of metal centers, e.g. $(C_5H_5)_2Ti.$ Ketones and aldehydes condense to give the heterocycles called dithianes:

    $C_6H_4(SH)_2$ + RR’CO → $C_6H_4(S)_2CRR’$ + $H_2O$

## Related compounds

3,4-Toluenedithiol, also called dimercaptotoluene (CAS#496-74-2), behaves similarly to 1,2-benzenedithiol but is a solid at ambient temperatures (m.p. 135-137 °C).

Alkene-1,2-dithiols are unstable, although metal complexes of alkene-1,2-dithiolates, called dithiolene complexes, are well known.

