Benzo-Bridged Bis(1,2,3-dithiazoles) and Their Selenium Analogues. Preparation, Molecular and Electronic Structures, and Redox Chemistry

The condensation of diaminobenzenedithiol with sulfur monochloride
leads to the chloride salt of the
radical cation of
3,6-dichlorobenzo[1,2-d:4,5-d‘]bis(1,2,3-dithiazole),
dichloro-[BB-123-DTA][Cl], which can be
reduced to neutral dichloro-[BB-123-DTA] with triphenylantimony.
A similar condensation with selenium tetrachloride
leads, upon reduction, to the corresponding
bis(1,2,3-thiaselenazole) dichloro-[BB-123-TSA]. The
crystal and
molecular structures of both compounds have been determined by X-ray
diffraction. Both compounds, which are
formally antiaromatic 16π-systems, exhibit internal bond lengths
consistent with a quinoid formulation. The radical
cations of both rings have been characterized by ESR spectroscopy; for
dichloro-[BB-123-DTA]+ g = 2.0114
and
aN = 0.201 mT, while for
dichloro-[BB-123-TSA]+ g = 2.021 and
aN = 0.44 mT. Further oxidation of both
rings
affords the corresponding dications, both of which have been
characterized crystallographically as their
AlCl4- salts.
The structural features of these compounds are consistent with
those expected for dithiazolylium (or thiaselenazolylium)
derivatives. The structure and redox chemistry of the
benzo[1,2-d:4,5-d‘]bis(1,2,3-dithiazole)
framework is discussed
in the light of the results of ab initio
calculations.