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Tribromophenol copper(II) complexes with ligands such as pyridine and ethylenediamine are known to polymerize thermally. Generally, high temperature is required for thermal polymerization of such complexes. Thermal polymerization of trihalophenol copper(II) complexes in toluene has an induction period of c. 30 min. Electroinitiated polymerization of trihalophenol copper(II) complexes has also been accomplished recently using pyridine or ethylenediamine as ligands. However, the above mentioned copper(II) complexes cannot be polymerized electro‐chemically in acetonitrile. When pyridine and ethylenediamine are used as ligands, such complexes rapidly polymerize in acetonitrile without the passage of any current even at room temperature. Therefore, the electrochemical polymerization of trihalophenol copper(II) complexes with pyridine and ethylenediamine ligands must be carried out in dimethylformamide. In the present work, electroinitiated polymerization of bis(2,4,6‐tribromo‐phenoxo)‐N,N,N′,N′‐tetramethylethylenediamine copper(II) complex (TBPTD) was accomplished for the first time in acetonitrile. When N,N,N′,N′‐tetramethylethylene diamine is used as the ligand in the preparation of tribromophenol copper(II) complex it is found that acetonitrile can be used as solvent. This complex does not polymerize in acetonitrile without the application of potential. Electroinitiated polymerization of TBPTD was carried out by constant potential electrolysis, at each anodic peak potential of the complex. These potentials of TBPTD were measured, in advance, by cyclic voltammetry in acetonitrile. Electrolysis of TBPTD yielded polymers in the anode compartment only. Electroinitated polymerization of this monomer exhibited no induction period in contrast to the case of thermal polymerization. The reacted monomer concentration was simultaneously followed by cyclic voltammetry, in the same electrolysis cell. This process was accomplished by a specially designed H‐type cell equipped with six electrodes. Use of cyclic voltammetry for simultaneous in‐situ monitoring of reacted monomer concentrations was found to be more accurate, quicker and more reproducible than gas chromatography or spectroscopy. Polymers were characterized by FTIR, 1HNMR, and 13CNMR spectral analyses as well as measurement of molecular weight by the isopiestic method.