Highly Active and Isospecific Styrene Polymerization Catalyzed by Zirconium Complexes Bearing Aryl-substituted [OSSO]-Type Bis(phenolate) Ligands.

[OSSO]-type dibenzyl zirconium(IV) complexes and possessing aryl substituents ortho to the phenoxide moieties (ortho substituents, phenyl and 2,6-dimethylphenyl (Dmp)) were synthesized and characterized. Upon activation with dMAO (dried methylaluminoxane), complex was found to promote highly isospecific styrene polymerizations ([] = 97.5%⁻99%) with high molecular weights up to 181,000 g·mmol. When the Dmp-substituted pre-catalyst /dMAO system was used, the highest activity, over 7700 g·mmol()·h, was recorded involving the formation of precisely isospecific polystyrenes of [] more than 99%.