Syntheses and Characterization of 1,3-Dithiepin-2-Carbodithiolate and Its Alkylated Derivatives

The synthesis and characterization of a new series of organo-sulfur compounds which contain the tetrathioethylene unit are reported. A single crystal structure study of one of these compounds, 2-(1,3-dithiolan-2-ylid-ene)-1,3-dithiepin was carried out. The crystals belong to space group P1 with α=8.634(2) Å, b=15.658(4) Å, c=8.196(2) Å, α=75.79(2)°, β=103.11(2)°, δ=102.70(2)°, R=0.058 for 1886 reflections I > 3 [sgrave](I), and D x=1.493, D m=1.46, for Z=4. The packing of molecules does show stacking with three close contacts between sulfurs having the following distances: 3.6477 Å, 3.5860 Å, and 3.5782 Å. Further characterization by 1H and 13C NMR, electrochemistry, and MO calculations show these compounds to be quite different from the parent TTF in many aspects.