Living polymerization of several substituted acetylenes by CpMoCl4-based catalysts

[(o-Trifluoromethyl)phenyl]acetylene polymerized in a living fashion in the presence of CpMoCl4–cocatalyst–EtOH catalysts (Cp: cyclopentadienyl; cocatalyst: EtMgBr, Et3Al, n-BuLi). The CpMoCl4–EtMgBr–EtOH (1:2:2) catalyst was particularly effective, with which the Mw/Mn of the formed polymer and the initiation efficiency, [P∗]/[Cat], were 1.06 and 7.6%, respectively. Further, [P∗]/[Cat] increased up to 10–13% at low temperatures (e.g. 0 °C) of catalyst aging and monomer addition. [(o-Trimethylsilyl)phenyl]acetylene also provided polymer having narrow molecular weight distributions with CpMoCl4–EtMgBr–EtOH (1:2:2). CpMoCl4 was more stable to air and moisture than MoOCl4 owing to the steric and electronic effects of the Cp ligand, while the activity of the CpMoCl4-based catalysts were lower than that of the MoOCl4-based counterparts.