Influence of thiopheneyl‐based twisted backbone on the properties of α‐diimine nickel catalysts in ethylene polymerization

Abstract

The modification of ligand sterics has become a prevalent strategy to tune the properties of α‐diimine‐type nickel catalysts. The majority of the works in this field focus on the modifications of the aniline moiety. In this contribution, we decide to explore the influence of backbone structures. Specifically, nickel complexes bearing 2,5‐dimethyl‐thien‐3‐yl and 2‐methyl‐5‐phenylthien‐3‐yl backbone structures were prepared and characterized. In comparison with the nickel analogue with methyl backbone, these new nickel complexes demonstrate much higher catalytic activity and thermal stability upto 80°C in ethylene polymerization and generate polymer products with much higher molecular weight along with lower branching density and higher melting points. It is believed that the bulky substituents at ligand backbone will exert influence on the N‐aryl moieties and increase steric bulkiness around the metal center. This backbone strategy is applicable for future studies in other catalytic reactions.

Ni(I) Intermediates Formed upon Activation of a Ni(II) α-Diimine Ethylene Polymerization Precatalyst with AlR3 (R = Me, Et, and iBu), AlR2Cl (R = Me, Et), and MMAO: A Comparative Study

“…α-Diimine Ni­(II) polymerization catalysts, discovered by Brookhart and co-workers, − have remained the subject of extensive studies because of their unique ability to mediate the formation of practically important products such as highly branched polyethylene from ethylene as the only feedstock and copolymers of ethylene with polar comonomers. − …”

Effect of N‐Aryl Para‐Benzhydryl Substituent on the Thermal Stability of α‐Diimine Nickel Catalyst

“…The branch DOI: 10.1002/marc.202300221 density of the product can be regulated by the modification of the catalyst structure and the adjustment of polymerization conditions, which has good application potential. [11][12][13][14][15][16] Over the past three decades, the modification of the catalyst structure has been the main research direction, such as the change in the N-aryl structure [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] or the backbone structure, [34][35][36][37][38][39][40][41][42][43][44] even the introduction of strong combination strategy. [45][46][47][48][49] Improving the catalyst thermal stability is what researchers are passionate about, which is related to the industrial application of catalysts, but there are few related pieces of research about the inactivation mechanism.…”

Ethylene homo and copolymerization by phosphorus‐benzoquinone based homogeneous and heterogeneous nickel catalysts

“…Due to the low oxophilicity of these metals, a series of catalysts with different ligand structures have been developed for the study of polar monomer copolymerization 16–29 . However, the development of nickel catalysts has the potential to offer enormous economic and environmental advantages over palladium 30–34 . From this perspective, nickel catalysts have been explored in a series of different coordination frameworks.…”

“…[16][17][18][19][20][21][22][23][24][25][26][27][28][29] However, the development of nickel catalysts has the potential to offer enormous economic and environmental advantages over palladium. [30][31][32][33][34] From this perspective, nickel catalysts have been explored in a series of different coordination frameworks. For example, [N, N] type catalysts such as α-diimine nickel can prepare polyolefins with branched chain structures and various polymer topologies due to their unique chain walking mechanism.…”