2,2'-Bi[benzo[b]thiophene]: an unexpected isolation of the benzo[b]thiophene dimer

The crystal structure of 2,2'-bi[benzo[b]thiophene], C16H10S2, at 173 K has triclinic (P1) symmetry. It is of interest with respect to its apparent mode of synthesis, as it is a by-product of a Stille cross-coupling reaction in which it was not explictly detected by spectroscopic methods. It was upon crystal structure analysis of a specimen isolated from the mother liquor that this reaction was determined to give rise to the title compound, which is a dimer arising from the starting material. Two independent half-molecules of this dimer comprise the asymmetric unit, and the full molecules are generated via inversion centers. Both molecules in the unit cell exhibit ring disorder, and they are essentially identical because of their rigidity and planarity.