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Tetrathiafulvalenes. XIX. Synthesis and Properties of Electron Conducting Poly‐Dithiolene Complexes with Ethylene Tetrathiolat and Tetrathiafulvalene Tetrathiolat as Bridge Ligands [1,3]‐Dithiolo[4,5‐d]‐1,3‐dithiol‐2,5‐dione 7 and 5‐(5‐oxo[1,3]‐dithiolo[4,5–d]1,3‐dithiole‐2‐ylidene)[1,3]‐dithiolo[4,5–d]1,3–dithiol‐2‐one 8 were synthesised from 1,3‐dithiole‐2‐thione‐4,5‐dithiolat. The ligands react with salts of iron, cobalt, nickel, palladium, platinum and copper to give the polymer complexes 22a–g and 23a–e, respectively. Irradiation of 7 in the presence of iron penta‐, dicobalt octa‐ or nickel tetracarbonyl gives the corresponding dithiolene complexes 21a–c. The amorphous insoluble polymer complexes from types 21, 22, and 23 have been characterised by i.r.‐spectroscopy, susceptibility and conductivity measurements. The nickel complexes have the highest electrical conductivity (σRT ∼ 10−1Ω−1cm−1, pellets) with a very low activation energy (0,045 eV, 100–300 K) A high electron delocalization in the direction of the polymer chain and an easy charge transfer from chain to chain is supposed.

The title compounds are generated and characterized in the gas phase by tandem mass spectrometry (neutralization‐reionization mass spectrometry); it is demonstrated that both even and odd‐numbered polycarbon disulfides S(Cn)S(n = 2–6) are stable species. The elusiveness of the even‐numbered analogues (n = 2, 4, 6) in the condensed phase must be due to facile intermolecular reactions.

Treatment of bis(4‐methoxybenzylthio)acetylene (1) with iodine monochloride yields different products in the presence or absence of nucleophiles such as water or alcohols. Normally, the electrophilic cyclisation of bis(benzylthio)acetylenes produces 1H‐2‐benzothiopyrans 2 by intramolecular ortho attack on the aromatic ring by a vinyl cation formed in situ (Ar2‐6 cyclisation). In the case of 1, however, the high electron density in the ipso position of the aromatic ring favours ipso attack (Ar1‐5 route). The fate of the ipso σ complex is determined by the presence or absence of nucleophiles in the reaction medium. When nucleophiles are excluded, the σ complex is stabilised by 1,2‐migration and formation of 1H‐2‐benzothiopyran 2a. In the presence of water, the σ complex yields spirocyclohexadienone dihydrothiophenes 3a and 3d. In the presence of 3‐methylbenzyl alcohol, the methoxy substituent of the 2‐benzothiopyran ring is exchanged by the 3‐methylbenzyloxy group in product 2d. These findings are consistent with the formation of 2a, 2c, 2d and 2f by ipso − and not ortho − attack on the 4‐methoxyphenyl ring. Similar results were obtained both with ICl and from a proton‐induced cyclisation. In one‐pot syntheses, 3a and 3d were transformed into 2‐benzothiopyrylium salts 4a and 4b by tritylium tetrafluoroborate, and 3a and 3b were rearranged into the 6‐hydroxy‐substituted 2‐benzothiopyrans 2b and 2g by proton catalysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)