Abstract
The dibenzyl zirconium(IV) complex (4) incorporating with a carbazolyl(Cbz)-substituted [OSSO]-type bis(phenolate) ligand was synthesized. Upon activation with dried modified methylaluminoxane (dMMAO), precatalyst 4 at relatively low catalyst loadings was found to promote the 1,2-regioselective oligomerization of 1-hexene to produce the corresponding vinylidene-ended oligomers with moderate turnover frequencies (TOFs) up to 2080 h−1. The 13C NMR analysis of the resulting oligomers revealed the formation of dimer-enriched oligo(1-hexene)s in 39–62% distributions. The precatalyst 4 with dried methylaluminoxane (dMAO) also exhibited good performance in the polymerization of styrene yielding isotactic polystyrenes ([mm] > 99%) with quite large molecular weights (Mw < 508,100 g mol−1) and relatively high catalytic activity (up to 2810 g mmol(4)−1 h−1).
Highlights
Since the discovery of Ziegler-Natta catalyst and single-site metallocene catalyst, the development of precise oligomerization and polymerization catalysts for α-olefins has been attractive in both academic and industrial fields [1,2,3,4]
We have preliminarily investigated the preparation of dibenzyl zirconium(IV) complexes (1 and 2) bearing [OSSO]-type bis(phenolate) ligands substituted with phenyl or 2,6-dimethylphenyl (Dmp) groups on the phenolate groups (Scheme 1) [46]
The weight average molecular weights (Mw ) and molecular weight distributions (Mw /Mn ) of the polymers were determined at ambient temperature using a GPC KF-804L (Shodex Corporation, Tokyo, Japan) gel permeation chromatograph (GPC)
Summary
Since the discovery of Ziegler-Natta catalyst and single-site metallocene catalyst, the development of precise oligomerization and polymerization catalysts for α-olefins has been attractive in both academic and industrial fields [1,2,3,4]. We have reported several Group 4 and 5 metal complexes having an original [OSSO]-type bis(phenolate) ligand possessing a trans-1,2-cyclooctanediyl platform [38,39,40,41,42,43,44,45]. The combination of these complexes and activators could achieve the controlled isotactic polymerization of various α-olefins involving excellent activity. Upon activation with dMAO (dried methylaluminoxane), the dibenzyl complexes 1 and 2 promote high performance in the polymerization of styrene (activity < 7700 g mmol(cat.)−1 h−1 )
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