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

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) angstrom) 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 pre-dominant 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 degrees C to 60 degrees 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.

Automated summary

Cobalt complexes carrying 2-acetyl-6-iminopyridine ligand were synthesized and characterized. These complexes showed high conversion rates and selectivities for the polymerization of isoprene, myrcene, and butadiene. The resulting poly(1,3-diene)s exhibited stable properties under various operational conditions.