Unimodal polyethylenes of high linearity and narrow dispersity by using ortho-4,4′-dichlorobenzhydryl-modified bis(imino)pyridyl-iron catalysts

Abstract

Six different examples of 4,4'-dichlorobenzhydryl-substituted 2,6-bis(arylimino)pyridyl-iron(II) chloride complex, [2-{{2,6-((p-ClPh)2CH)2-4-MeC6H2}N=CMe}-6-(ArN=CMe)C5H3N]FeCl2 (Ar = 2,6-Me2C6H3 Fe1, 2,6-Et2C6H3 Fe2, 2,6-iPr2C6H3 Fe3, 2,4,6-Me3C6H2 Fe4, 2,6-Et2-4-MeC6H2 Fe5, 2,6-((p-ClPh)2CH)2-4-MeC6H2 Fe6), have been synthesized in good yield and...

Research Progress of Iron Catalysts with N,N,N‐tridentate Ligands for Ethylene Polymerization

“…[55] These catalysts can effectively regulate the molecular weight of PE (M w range: 0.91-3.94×10 5 g/mol) using MAO as activator (Table 2, entry 19). [56] Besides that, similar ligand catalysts 20 bearing ortho-4,4'-dichlorobenzhydryl were reported and exhibited high catalytic activities (2.16×10 7 g PE/(mol Fe•h)) for ethylene polymerization (Table 2, entry 20). The data of previous catalyst properties are obtained within the reaction time of 30 minutes, while the catalysts 20 has a long catalytic life (catalytic activities up to 1.08×10 7 g PE/(mol Fe•h) after 1 hour).…”

“…explored a variety of iron complexes 19 a – e bearing trifluoromethoxy and diphenylbenzyl substituents to realize a combination of steric tuning and electronic modulation [55] . These catalysts can effectively regulate the molecular weight of PE (M w range: 0.91–3.94×10 5 g/mol) using MAO as activator (Table 2, entry 19) [56] . Besides that, similar ligand catalysts 20 bearing ortho‐ 4,4’‐dichlorobenzhydryl were reported and exhibited high catalytic activities (2.16×10 7 g PE/(mol Fe⋅h)) for ethylene polymerization (Table 2, entry 20).…”

Non-Symmetrically Fused Bis(arylimino)pyridines with para-Phenyl Substitution: Exploring Their Use as N′,N,N″-Supports in Iron Ethylene Polymerization Catalysis

“…All catalysts displayed high activity (range: 7.64-34.10 × 10 6 g (PE) mol −1 (Fe) h −1 ), with the relative order being: 7). These results suggest that less bulky ortho-R 1 groups are, in general, beneficial to the process of ethylene coordination/migratory insertion [24,30,35]. Nevertheless, it is evident that there are some anomalies in this structure/activity correlation, which could be attributable to the long-range effect of the para-phenyl group on carbocyclic ring flexibility and, in turn, N-aryl group binding/inclination [29].…”

“…On analysis of their relative performance, the catalytic activity decreased in the following order: S4). As is evident, the precatalysts bearing the least bulky substituents in the ortho positions of the N-aryl groups, Fe4 and Fe1, exhibited higher activity due to the faster rates of ethylene insertion and chain propagation [24,30,35]. Moreover, mesityl-containing Fe4 produced the highest molecular weight polyethylene of the series, which was also seen for the MMAO runs, but nonetheless unexpected when compared with previous work in which the most sterically hindered complex usually affords the highest molecular weight polymer.…”

π–π Interactions-Driven Ethylene Polymerization Using “Sandwich” Bis(imino)pyridyl Iron Catalysts

“…As highly active ethylene polymerization/oligomerization catalysts, bis­(imino)­pyridyl iron catalysts have received intensive attention due to their nontoxic, high metal abundance, and insensitivity to air and moisture. − In contrast to α-diimine nickel/palladium catalysts, bis­(imino)­pyridyl iron catalysts produced fully linear products. − The demand for bulk ortho -aryl substituents is a crucial factor in suppressing β-H elimination and β-H transfer to monomer, which usually contributes to high-molecular-weight polyethylene with a bimodal distribution due to two chain transfer pathways involving β-H transfer to monomer (high-molecular-weight fraction) and chain transfer to aluminum (low-molecular-weight fraction). , However, bulk ortho -aryl substituents often decrease the activity of bis­(imino)­pyridyl iron catalyst because the bulky steric hindrance around the metal center hinders the coordination and insertion of ethylene monomers. − …”