A New Monomer for π‐Conjugated Polymers — Synthesis and Characterization of Bis(( Z )‐5‐phenyl‐2‐phenylmethylidene‐1, 3‐dithiole‐4‐yl)monosulfane

Bis(( Z )‐5‐phenyl‐2‐phenylmethylidene‐1, 3‐dithiole‐4‐yl)monosulfane ( 6 ), a molecule consisting of two diphenyldithiafulvene units connected by a sulfur bridge, was synthesized by the selective lithiation of ( Z )‐4‐phenyl‐2‐phenylmethylidene‐1, 3‐dithiole ( 7a ) at the endocyclic double bond and by subsequent reaction of the lithiated intermediate with bis(phenylsulfonyl)sulfane. Since this reaction sequence proceeded with retention of configuration, of three possible isomers ( E , E , Z , E , and Z , Z ) only the Z , Z form was obtained. On the basis of the X‐ray structure analysis and the NMR‐spectroscopic characterization of 6 supplemented by the NMR parameters of ( E )‐ and ( Z )‐4‐phenyl‐2‐phenylmethylidene‐1, 3‐dithiole, it was demonstrated that two characteristic 5 J coupling constants of the proton at the exocyclic double bond indicate the configuration ( Z or E ) of disubstituted dithiafuvene derivatives.