Cis -1,4-specific isoprene polymerization and isoprene-styrene copolymerization using nickel dichloride complexes with mono- or bidentate benzimidazole ligands

Abstract In the presence of Al(C8H17)3 and [Ph3C][B(C6F5)4], 2-methylbenzimidazole- or phenylbis(benzimidazol-2-yl)methane-ligated nickel dichloride complexes 1 and 2, the former of which was newly synthesized in this study, were found to catalyze the homopolymerization of isoprene (Ip) and styrene (St), respectively. The stereospecificities of the produced polymers (cis-1,4-polyIp; 1: 97%, 2: 95%; isotactic (mm)-enriched-polySt; 1: 42%, 2: 45%) depend on the structures of the complexes. The 1- or 2-catalyzed copolymerization reactions of Ip with St were also investigated. The reactivity ratios between Ip and St were determined from the Fineman–Ross plots (1: rIp = 0.81, rSt = 2.04; 2: rIp = 2.07, rSt = 2.35). These results suggest that complex 1 produces predominantly random copolymers, whereas complex 2 tends to multiblock-like structures of the resultant copolymers.