Ethylene polymerization catalyzed by dinickel complexes with a double-decker structure

Abstract

Double-decker dinickel catalysts, even without any substituent on an ortho-position, afforded high molecular weight polyethylene with high crystallinity and less branching.

Copolymerization of Ethylene and Long-Chain Functional α-Olefins by Dinuclear Zirconium Catalysts

“…Multimetallic catalysts have been pursued as a method for synthesizing functionalized polyethylene via a direct copolymerization of ethylene and polar monomers . Examples of bimetallic catalysts with rigid linkers that feature improved performance include enhanced incorporation of functionalized norbornenes using dinickel catalysts ( A ; Figure ), higher incorporation of ester-containing comonomers and acrylic anhydride using macrocyclic frameworks to support “double-decker” dinickel or dipalladium catalysts with phenoxy-imine ( B ) or α-diimine ( C ) donors, − and increased tolerance to amine additives and incorporation of amino olefins by terphenyl-supported bis­(phenoxy-imine)­dinickel catalysts ( D ). − Bimetallic catalysts displaying early transition metals have been demonstrated to affect performance by increasing the incorporation of α-olefins ( E and F ), − though not those containing polar groups. A bimetallic mechanism of α-olefin incorporation was proposed where distal C–H bonds interact with the second metal to facilitate enchainment. − ,− An analogous bimetallic mechanism for comonomer incorporation is particularly appealing for polar olefins.…”

Double-Decker-Type Dipalladium Catalysts for Copolymerization of Ethylene with Acrylic Anhydride

“…We reported the dinickel complexes with a similar double-decker structure as 1 catalyze copolymerization of ethylene with terminal dienes and unsaturated esters, having three or four carbon atoms between the vinyl and/or oxygen atoms, and achieved the polymers with high content of the bifunctional comonomer. 32,33 The remained vinyl group coordinates to the Pd center (intermediate C) and undergoes 1,2-insertion to the chain end to form unit X. Cyclization to form trans-fused five-membered ring is favored over the cis-cyclization, similarly to the cyclopolymerization of 1 The intermediate B can also undergo β-hydrogen elimination, leading to chain walking of the growing terminal to form stable six-membered chelate complex (intermediate E), as shown in Scheme 1b. This pathway should be fast in the monopalladium complex, where the uncyclized acrylic anhydride group is located at the terminal of the branches (unit Y′).…”

“…It is ascribed to preformation of intermediate A with double coordination of the monomer by the two palladium centers. We reported the dinickel complexes with a similar double-decker structure as 1 catalyze copolymerization of ethylene with terminal dienes and unsaturated esters, having three or four carbon atoms between the vinyl and/or oxygen atoms, and achieved the polymers with high content of the bifunctional comonomer. , The remained vinyl group coordinates to the Pd center (intermediate C ) and undergoes 1,2-insertion to the chain end to form unit X . Cyclization to form trans -fused five-membered ring is favored over the cis -cyclization, similarly to the cyclopolymerization of 1,6-heptadienes by diimine Pd complexes.…”

Olefin Polymerization and Copolymerization Catalyzed by Dinuclear Catalysts Having Macrocyclic Ligands

“…The dinickel complex Ni 2 (L4b) brought about ethylene polymerization in the presence of Ni(cod) 2 as a phosphine scavenger. 30 The catalytic activity of Ni 2 (L4b) was higher than that of the mononickel complex Ni(L7b). The molecular weight of the produced polyethylene was much higher than that obtained using Ni(L7b), and had a wider molecular weight distribution.…”