Short intermolecular S...S contacts in a reaction product from the cyclic sulfate ester of dimethyl L-tartrate and 2-thioxo-1,3-dithiole-4,5-dithiolate.

Cyclic sulfate ester 6 reacts with dithiolate 4 to give dl cyclic products 8 and 9. The crystal of 9 shows two short S...S intermolecular interaction (<3.4 Å) between trithiocarbonate groups, due to cooperative polarisations and the highly asymmetric shape of the bonded S atom. The latter effect is mainly responsible for the 'short' S...S contacts in ET's radical cation salts. In contrast to similar systems, the sp³ C atoms of the six-membered ring in 9 are displaced to the same side of the dithiole plane.