Polymerization of isoprene, myrcene, and butadiene catalyzed by cobalt complexes supported with 2‐acetyl‐6‐iminopyridine ligand

Abstract

Cobalt complexes carrying 2‐acetyl‐6‐iminopyridine ligand are synthesized and characterized. Single‐crystal X‐ray diffraction reveals the cobalt ion is chelated with two nitrogen atoms and an acetyl oxygen atom additionally. A significant prolonged Co–O distance (2.3960(57) Å) is found, indicative of a labile character. Activated by diethylchloroaluminum, all complexes show high conversion rates for isoprene and myrcene polymerizations, affording cis‐1,4/3,4 regulated 1,3‐diene polymers. The polymerization of butadiene, interestingly, gives predominant cis‐1,4 selectivity (>99.2%) with moderate activity. The substituent at ortho‐position of arylimine plays a minor role in controlling activity and selectivity as well as the molecular weight of the resultant polymers. The properties of resultant poly(1,3‐diene)s are stable even in a wide range of operational conditions, such as [Al]/[Co] varied from 20 to 600, temperature spanning from 0°C to 60°C, and monomer–catalyst ratio from 1000 to 4000. These additional benefits of minimum fluctuation in catalytic performances may be suitable for industrial polymerization process.