To understand the charge transport ability of metal coordinated cyclobutadiene, a series of cyclobutadiene cobalt cyclopentadiene (CbCoCp) complexes contg. electrochem. polymerizable 3,4-ethylenedioxythiophene units were synthesized. The complexes were electrochem. polymd. and the resulting polythiophenes were characterized by cyclic voltammetry, in situ cond. and UV-vis spectroelectrochem. Several different derivs. of the CbCoCp complexes and a model study suggested that if the oxidn. of the org. fragment was above CoI/II redox couple of the CbCoCp complex, detrimental side reactions occurred. Side reactions did not occur if the oxidn. potential of the org. fragment was below the oxidn. potential of the metal. [on SciFinder(R)]