Photoresponsive Palladium and Nickel Catalysts for Ethylene Polymerization and Copolymerization

Abstract

In this contribution, we install an azobenzene functionality in olefin polymerization catalysts and use light to modulate their properties via photoinduced trans–cis isomerization of the azobenzene moiety. The initially targeted azobenzene‐functionalized α‐diimine palladium and nickel catalysts are not photoresponsive. To address this issue, an imine–amine system bearing interrupted conjugation with the metal center, and a sandwich‐type α‐diimine system bearing an azobenzene unit at a position covalently far from the metal center were prepared and studied. We demonstrate that light can be used to tune their properties in ethylene polymerization and copolymerization with polar comonomers, enabling light‐induced control of the polymerization processes, polymer microstructures and polymer properties. More interestingly, the light‐mediated property changes were attributed to ligand electronic effects in one system and ligand steric effects in the other.

cis-1,4 Selective Coordination Polymerization of 1,3-Butadiene and Copolymerization with Polar 2-(4-Methoxyphenyl)-1,3-butadiene by Acenaphthene-Based α-Diimine Cobalt Complexes Featuring Intra-Ligand π-π Stacking Interactions

“…As expected, a distorted tetrahedron geometry was observed for complex Co1, and the bond angles and bond distances in L2 and Co1 are typical for previously reported α-diimine Co(II) complexes [22][23][24]. For the ligand L2, both imine groups revealed E,E-configurations, which were different from some of the previous literature, which stated that E,Z-configurations were adopted [25][26][27][28]. Such a difference was probably due to the intra-ligand π,π-interactions that were found between the acenaphthenyl plane and the phenyl rings on the dibenzhydryl groups, which favored the E,E-configuration as the more thermodynamically stable state.…”

Unprecedented Square-Planar α-Diimine Dibromonickel Complexes and Their Ethylene Polymerizations Modulated by Ni–Phenyl Interactions

“…Significant advances have been made in steric modifications of the ortho -bis-aryl substituents for improving olefin polymerization properties (Figure ). ,− In addition to “classic” 2,6-diisopropylaniline, , 8-aryl­naphthylamine moieties lead to the unique sandwich geometry of α-diimine Ni/Pd complexes, in which the 8-aryl substituents lie perpendicular to the naphthyl groups and are nearly parallel to the square coordination plane. ,− The bulky backbone is an alternative access to improving the steric hindrance of α-diimine Ni/Pd complexes . In addition to traditional dimethyl and acenaphthylene backbones, , our group and other research groups have developed camphyl, − dibenzobarrelene, − and dinaphthobarrelene backbone-based α-diimine nickel precatalysts .…”

Influence of Silica-Supported Alkylaluminum on Heterogeneous Zwitterionic Anilinonaphthoquinone Nickel and Palladium-Catalyzed Ethylene Polymerization and Copolymerization with Polar Monomers

“…Palladium- and nickel-based late transition metal catalysts have developed rapidly in recent years due to their lower electrophilicity compared with early transition metal catalysts and thus have gained superiority in catalyzing the direct copolymerization of olefin and polar monomers to produce functional polyolefins. − However, it is rather difficult to achieve the industrial production of functional polyolefins using homogeneous late transition metal catalysts due to some serious shortcomings, such as uncontrolled polymer morphology and serious reactor fouling. The heterogenization of homogeneous late transition metal catalysts has been considered as a promising pathway to overcome the above problems. − …”