Highly active and trans-1,4-specific polymerization of 1,3-butadiene catalyzed by bis(benzimidazolyl)amine chromium complexes activated with methylaluminoxane

A family of Cr(III) complexes supported on tridentate dibenzimidazolyl ligands having a general formula: [N(CH3)(CH2)2(Bm-R)2]CrCl3 [where Bm = benzimidazolyl, R = H (3a); -Me(3b); -Bn (3c)] have been synthesized and utilized them for the trans-1,4-specific polymerizations of 1,3-butadiene (BD), activated with methylalumoxane (MAO). The activity of BD polymerizations was sensitive to the type of ligand on the Cr metal, so that the activity decreases in the order of 3a > 3c > 3b. All the catalysts combined with MAO yielded polybutadienes with perfect trans-1,4 structure with moderate molecular weight.