Enantio‐ and Stereoselective Cyclopolymerization of Hexa‐1,5‐diene Catalyzed by Zirconium Complexes Possessing Optically Active Bis(phenolato) Ligands

Abstract

Enantio- and stereoselective cyclopolymerization of hexa-1,5-diene was achieved by enantiomerically pure dichloro zirconium(IV) pre-catalysts 2 possessing chiral [OSSO]-type bis(phenolate) ligands (-)-1 and (+)-1 in combination with dried methylaluminoxane (dMAO) as an activator. The corresponding activities were recorded with quite high values up to 1,960 g mmol(2) h , which are extremely larger than those of the related complexes. The microstructure analysis for the PMCPs furnished by pre-catalysts (Λ,S,S)-2 and (Δ,R,R)-2 showed good isotacticity factors (α = 75-78%) and relatively high proportions of trans-cyclopentane rings (σ = 14-21%). These enantiomeric PMCPs exhibited large specific optical rotations ([α] = +28 to +32° from (Λ,S,S)-2, -26 to -34° from (Δ,R,R)-2).

Scandium-Catalyzed Regio- and Stereoselective Cyclopolymerization of Functionalized α,ω-Dienes and Copolymerization with Ethylene

“…Cyclic polyolefins bearing heteroatom functional groups are of special interest, as they may show improved beneficial properties compared to the heteroatom-free polymers. The cyclopolymerization of α,ω-dienes such as 1,5-hexadiene and 1,6-heptadiene by transition metal catalysts has demonstrated particular utility for the preparation of cyclopolyolefins. − In this transformation, the precise control of the regio- and stereochemistry is highly important to obtain high-performance polymers. However, compared to the polymerization of unsubstituted α,ω-dienes, it is usually difficult to control the regio- and stereoselectivity of the cyclopolymerization of heteroatom-functionalized α,ω-dienes, because of the lack of suitable catalysts that can not only show good compatibility with the heteroatom functional group but can also govern the stereochemistry of the heteroatom-substituent in addition to the regio- and stereoselectivity control of the common cyclization process.…”

Carbazolyl-Substituted [OSSO]-Type Zirconium(IV) Complex as a Precatalyst for the Oligomerization and Polymerization of α-Olefins

“…Among them, dianionic [OSSO]-type tetradentate ligands, based on two phenoxide frameworks with two sulfur donors at the ortho-or benzyl-positions have been of great interest so far . 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.…”

Highly Efficient and 1,2-Regioselective Method for the Oligomerization of 1-Hexene Promoted by Zirconium Precatalysts with [OSSO]-Type Bis(phenolate) Ligands

“…Recently, our group reported several zirconium complexes that contain an [OSSO]-type bis­(phenolate) ligand based on a trans -1,2-cyclooctanediyl core. These complexes serve as precise polymerization catalysts for α-olefins and yield excellent isotactic poly­(α-olefin)­s. , Motivated by these results and the desire to further explore reactions catalyzed by [OSSO]-type complexes, we would like to report herein the high performance of dried-modified methylaluminoxane-activated (dMMAO) zirconium precatalysts 7 and 8 , which possess [OSSO]-type ancillary ligands with ortho , para -diphenylphenol or ortho -{2,6-dimethylphenyl (Dmp)}- para -methylphenol substituents, respectively, in the 1,2-regioselective oligomerization of 1-hexene using relatively low catalyst loadings …”