Preparation,structure, and reactivity of 1,3,4,6-tetrakis-(isopropylthio)thieno[3,4-c]thiophene-palladium complex with tetracyanoethylene

The reaction of 1,3,4,6-tetrakis(isopropylthio)thieno[3,4-c]thiophene ( 1 ) with the palladium complex Pd₂(dba)₃CHCl₃ (dba = dibenzylideneacetone) and tetracyanoethylene (TCNE) gave a new palladium complex in which two isopropylthio groups of 1 and the double bond of TCNE were trigonally coordinated to palladium. The X-ray analysis revealed the electron donation from palladium to TCNE, leading to a lengthening of the C?C double bond in TCNE and distortion of TCNE from planarity. The radical cation of 1 and the radical anion of TCNE were detected by ESR spectroscopy in methylene dichloride solution of the complex, although the radical content was estimated from the paramagnetic susceptibility to be less than 1%. The reaction of the complex with aniline gave the same product as that in the reaction of the radical cation of 1 with aniline.