Cis-1,4-specific polymerization of 1,3-conjugated dienes with bis(benzimidazole)NiCl2 catalyst system

We report herein that the catalytic system composed of a bis(benzimidazole)NiCl₂ complex (1, bis(benzimidazole) = phenylbis(benzimidazol-2-yl)methane), Al(C₈H₁₇)₃ (AlOct₃), and [Ph₃C][B(C₆F₅)₄] mediates highly cis-1,4-specific (up to 95 %) polymerization of isoprene (IP). This is the first nickel complex-based catalyst system that achieved the cis-1,4-specific IP polymerization with a selectivity of more than 90 %. The effects of AlR₃ (R = ⁱBu, Et, Me), AlEt₂Cl and activator ([PhNMe₂H][B(C₆F₅)₄], B(C₆F₅)₃, MAO) on the polymerization behavior were also investigated. The 1/AlOct₃/[Ph₃C][B(C₆F₅)₄] system also catalyzed the cis-1,4-specific polymerization of other 1,3-conjugated dienes such as 1,3-butadiene (BD), (E)-1,3-pentadiene (EPD) and β-myrcene (MY) (up to 92 % for BD, 84 % for EPD and 72 % for MY).