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 (σ RT ∼ 10 −1 Ω −1 cm −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.