Synthesis, structure, and butadiene polymerization behavior of alkylphosphine cobalt(II) complexes

The synthesis, characterization and behavior in polymerization of 1,3-butadiene of some cobalt(II) phosphine complexes (CoCl2(PEt3)(2), CoCl2((PPr3)-Pr-n)(2), CoCl2(PCy2H)(2), CoCl2((PBu2H)-Bu-t)(2), CoCl2((PBu2Me)-Bu-t)(2), CoCl2(PCyp(3))(2), CoCl2(PCy3)(2); Et=ethyl, Pr-n=normal-propyl, Cy =cyclohexyl, Bu-t = tert-butyl, Cyp =cyclopentyl) are described. The X-ray diffraction studies of CoCl2(PCy3)(2) and CoCl2(PCy2H)(2) are reported. Treatment of these complexes with methylaluminoxane, (MAO) leads to highly active butadiene polymerization catalysts; polymers having different microstructure have been obtained depending on the type of phosphine ligand bonded to the cobalt atom. An interpretation for this particular behavior, based on the 1,3-dienes polymerization mechanism previously proposed, is given.