Synthesis, characterization and ethylene oligomerization behavior of 2-(chloro-substituted-1H-benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridylnickel dihalides

Recent advances in Ni-mediated ethylene chain growth: Nimine-donor ligand effects on catalytic activity, thermal stability and oligo-/polymer structure

“…The discovery of α-diimine-nickel(II) catalysts by Brookhart and co-workers more than two decades ago has proved to be a milestone in the evolution of late transition [78,79] 2-Imino-6-benzimidazolyl/benzoxazolyl-pyridine-nickel pre-catalysts, 46 [92,[112][113][114][115] . Bis(α-diimine) dinuclear nickel pre-catalysts, 51a and 51b [119] .…”

“…In addition, complexes containing electron withdrawing substituents at the N-aryl group showed lower activity than that with alkyl substituents [92,[112][113][114][115]. As has been observed elsewhere the addition of PPh3 resulted in better catalytic activities toward ethylene oligomerization; a plausible role of the PPh3 is to stabilize the catalytically active species while being labile enough to provide a site for ethylene coordination [92,[112][113].…”

“…A [114,115], displayed a higher activity (10 6 g mol -1 (Ni) h -1 ) than the N-alkylated 46 [110,111]. In addition, complexes containing electron withdrawing substituents at the N-aryl group showed lower activity than that with alkyl substituents [92,[112][113][114][115].…”

Recent progress on nickel-based systems for ethylene oligo-/polymerization catalysis

“…Additionally, in the presence of 20 equivalents1` of PPh 3 , the activities of all investigated complexes increased dramatically with lower selectivities for 1-butene. 94 Scheme 55 N,N,N-tri-dentate nickel complexes 92 and 93a,b 59,[95][96][97] Our group has investigated the properties of the ethylene oligomerzation by the nickel complexes 92 and 93a,b (Scheme 55) bearing a benzimidazolyl group. 59,[95][96][97] With the addition of Et 2 AlCl as co-catalyst, all the nickel complexes 92 and 93a,b exhibited good catalytic activities of up to 10 6 g mol -1 (Ni) h -1 for ethylene oligomerization.…”

“…The steric and electronic effects of the ligands had a significant influence on the catalytic activities of the nickel complexes. 59,[95][96][97] The nickel complexes containing an isopropyl group on the benzimidazole instead of a methyl group performed with lower catalytic activities, 59,95 whilst the complexes that contain an N-H group on the benzimidazole exhibited a higher activity than those containing alkylated benzimidazoles. 59,[95][96][97] Variation of the R 1 group at the ortho positions of the imino-N aryl ring resulted in a strong influence on the catalytic performance.…”