Abstract
[OSSO]-type dibenzyl zirconium(IV) complexes 9 and 10 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 9 was found to promote highly isospecific styrene polymerizations ([mm] = 97.5%–99%) with high molecular weights Mw up to 181,000 g·mmol−1. When the Dmp-substituted pre-catalyst 10/dMAO system was used, the highest activity, over 7700 g·mmol(10)−1·h−1, was recorded involving the formation of precisely isospecific polystyrenes of [mm] more than 99%.
Highlights
Stereo-controlled polystyrene such as syndiotactic and isotactic polystyrenes is one of the most versatile polymeric materials, owing to its high melting point, high crystallinity, and excellent resistance to heat and chemicals [1,2]
Since the syndiospecific polymerization of styrene catalyzed by homogeneous CpTiCl3 /MAO system was discovered by Ishihara and coworkers at Idemitsu
1,4-dithiabutane-bridged [OSSO]-type bis(phenolate) ligand catalyzes the styrene polymerization with good activity (330 gmmol(1a) ́1 ̈ h1 ) to yield ultra-high molecular weight isotactic polystyrene (Mw = 5,300,000 gmol1 ) [36,37]
Summary
Stereo-controlled polystyrene such as syndiotactic (sPS) and isotactic polystyrenes (iPS) is one of the most versatile polymeric materials, owing to its high melting point, high crystallinity, and excellent resistance to heat and chemicals [1,2]. Since the syndiospecific polymerization of styrene catalyzed by homogeneous CpTiCl3 /MAO system was discovered by Ishihara and coworkers at Idemitsu. Okuda et al reported that MAO-activated titanium complex 1a supported by. 1,4-dithiabutane-bridged [OSSO]-type bis(phenolate) ligand catalyzes the styrene polymerization with good activity (330 gmmol(1a) ́1 ̈ h1 ) to yield ultra-high molecular weight isotactic polystyrene (Mw = 5,300,000 gmol1 ) [36,37]. Very recently, they demonstrated that thermally stable robust zirconium complex 2 possessing a dicumyl-substituted [OSSO]-type bis(phenolate) ligand can efficiently polymerize styrene in living fashion giving highly isotactic poly(styrene) ([mm] > 99%)
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