Abstract
Co and Ni complexes having the 6,6'-dihydroxy-2,2'-bipyridine (DHBP) ligand [CoCl(2)(dhbp), NiBr(2)(dhbp)] in the presence of organoaluminum cocatalysts showed much higher catalytic activity in 1,3-butadiene polymerization than the complexes having the 2,2'-bipyridine or 6,6'-dimethoxy-2,2'-bipyridine ligand without hydroxy groups. The polybutadienes obtained had 1,4-cis structure (up to 94.6%). In contrast, addition of 5-norbornene-2-methyl amine in 1,3-butadiene polymerization catalyzed by NiBr(2)(dhbp)/methylaluminoxane (MAO) caused a marked change in the microstructure of the polybutadiene to the iso-1,2-structure with high chemo- and stereoselectivities (mm > 99%).