Enhancing performance of α‐diiminonickel precatalyst for ethylene polymerization by substitution with the 2,4‐bis(4,4'‐dimethoxybenzhydryl)‐6‐methylphenyl group

Abstract

High activities in ethylene polymerization predetermine α‐diiminonickel precatalysts for potential industrial applications. In our study, we have synthesized and characterized a series of unsymmetrical 1‐(2,4‐bis(4,4′‐dimethoxybenzhydryl)‐6‐MeC6H2N)‐2‐arylimino‐acenaphthylene nickel(II) halides. The single‐crystal X‐ray diffraction study of representative compounds reveals distorted tetrahedral geometry. On activation with either Me2AlCl or modified methylaluminoxane, these nickel complexes exhibit high activities of the order of 106 g of PE (mol of Ni)−1 h−1 and produce polyethylene of generic application characterized by high molecular weight, narrow molecular weight distribution, and moderate degree of branching. The substituents at the ligands affect the catalytic performance of the nickel complexes and tune the microstructure of the resultant polyethylene.

Trifluoromethoxy-substituted nickel catalysts for producing highly branched polyethylenes: impact of solvent, activator andN,N′-ligand on polymer properties

“…Firstly, 2,6-dibenzhydryl-4-(trifluoromethoxy)aniline was obtained by a Friedel–Crafts alkylation of p -trifluoromethoxyaniline in the presence of zinc( ii ) chloride. 1–4 Secondly, acenaphthylene-1,2-dione was condensed with one equivalent of 2,6-dibenzhydryl-4-(trifluoromethoxy)aniline under acid catalyzed conditions to form the imine-ketone intermediate, 2,6-[(dibenzhydryl-4-trifluoromethoxyphenyl)imino]acenaphthylen-1-one. Finally, this imine-ketone was utilized in a second condensation reaction with the corresponding aniline to form L1–L5 .…”

“…α-Diimine complexes of nickel and palladium have a distinguished place in late transition polymerization catalysis ever since Brookhart and co-workers first recognized their effectiveness as single-site catalysts for the homo-polymerization of ethylene to branched polyolefins. 1–4 Of particular note is the ability of these catalysts to promote the displacement of the metal center along the growing polymer chain by a process commonly termed “chain walking”. 5 Indeed, the resulting branched polymeric materials display a wide range of promising properties.…”

“…22 Besides the crucial role played by the chelating ligand on catalytic activity and polymer properties, polymerization conditions such as solvent, co-catalyst and run temperature have also a key part to play. 2,20,23 With regard to reaction solvent, toluene has generally been employed in previous nickel-mediated ethylene polymerization, while only few studies have been undertaken with alternative solvents ( e.g. , hexane).…”

6-Arylimino-2-(2-(1-phenylethyl)naphthalen-1-yl)-iminopyridylmetal (Fe and Co) Complexes as Highly Active Precatalysts for Ethylene Polymerization: Influence of Metal and/or Substituents on the Active, Thermostable Performance of Their Complexes and Resultant Polyethylenes

“…Late-transition metal precatalysts have made great progress toward ethylene polymerization since the pioneering studies initiated by Brookhart and Gibson [ 1 , 2 , 3 , 4 , 5 , 6 ]. In addition to the α-diimino-nickel and palladium precatalysts [ 7 , 8 , 9 , 10 , 11 , 12 ], iron and cobalt precatalysts have showed a higher activity in ethylene polymerization and generated polyethylenes with highly linear structures [ 13 , 14 , 15 , 16 , 17 , 18 ]. However, the poor thermostability of iron and cobalt precatalysts and broad molecular weight distribution of obtained polyethylenes impeded further applications in the industry [ 19 , 20 ].…”

Trapping the Short-Chain Odd Carbon Number Olefins Using Nickel(II)-catalyzed Tandem Ethylene Oligomerization and Friedel-Crafts Alkylation of Toluene

“…Recently the area of nickel-catalyzed oligomerization and polymerization of olefins received a new boost. Nickel complexes are being widely employed for processes of chain-walking ethylene polymerization [4,5,[14][15][16][17][18][19][20][21][22][23]6,[24][25][26][27][7][8][9][10][11][12][13] and copolymerization of ethylene with polar monomers [22,24,[35][36][37][38][39][40][41][42][43][44][27][28][29][30][31][32][33][34]. However, the interest in the development of new nickel-based catalytic systems for ethylene oligomerization is still high [4,6,[53][54]…”