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

Abstract

[OSSO]-type dibenzyl zirconium(IV) complexes <b>9</b> and <b>10</b> 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 <b>9</b> was found to promote highly isospecific styrene polymerizations ([<i>mm</i>] = 97.5%⁻99%) with high molecular weights <i>M</i>_w up to 181,000 g·mmol^-1. When the Dmp-substituted pre-catalyst <b>10</b>/dMAO system was used, the highest activity, over 7700 g·mmol(<b>10</b>)^-1·h^-1, was recorded involving the formation of precisely isospecific polystyrenes of [<i>mm</i>] more than 99%.