Fluorinated 2,6-bis(arylimino)pyridyl iron complexes targeting bimodal dispersive polyethylenes: probing chain termination pathways via a combined experimental and DFT study

Abstract

The fluorinated 2,6-bis(arylimino)pyridyl iron (II) complexes, [2-[CMeN{2,4-{(4-FC6H4)2CH}2-6-F}]-6-(CMeNAr)C5H3N]FeCl2 (Ar = 2,6-Me2C6H3 Fe1, 2,6-Et2C6H3 Fe2, 2,6-iPr2C6H3 Fe3, 2,4,6-Me3C6H2 Fe4, and 2,6-Et2-4-MeC6H2 Fe5) and [2-[CMeN{2-{(4-FC6H4)2CH}-4-{(C6H5)CHAr’}-6-F}]-6-(CMeN(2,6-iPr2C6H3))C5H3N] FeCl2 (Ar’ = 3-(4-FC6H4)2CH}2-4-NH2-5-FC6H2 Fe6), being verified with...

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

“…Evidently, the latter observation highlights the involvement of β-H elimination to metal or monomer during chain termination [24]. Moreover, by considering the integral ratio of vinyl H b to methyl chain-end H f (1/18.82) [29,37,38], the molar ratio of the unsaturated polymer chain to the saturated polymer chain can be determined as 0.379 (see SI), a value that implies the additional presence of a fully saturated polymer in line with chain transfer to aluminum being also operational [4,5]. Further support for these assignments was provided by the 13 C NMR spectrum, which reveals a high-intensity peak around δ 29.43 ppm, which corresponds to the -(CH 2 ) n -repeat unit, along with lower intensity peaks at δ 13.72, 22.38, and 31.66 ppm for an n-propyl end-group and weaker downfield peaks at δ 113.85 and 138.78 ppm for a terminal vinyl group (Figure 10) [24].…”

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

“…Kwon and Sun studied the reaction mechanism of ethylene polymerization by 1 H/ 13 C Nuclear Magnetic Resonance (NMR) and Density Functional Theory (DFT). [62][63][64] It was found that β-H transfer to aluminum and β-H elimination was the main chain termination pathway, while there also occurred β-H transfer to metal/monomer. There is no difference in the kinetic behavior of β-H transfer to metal and to the monomer, both were proportional to the first square of monomer concentration, and produced vinyl-terminated PE.…”

“…Kwon and Sun studied the reaction mechanism of ethylene polymerization by 1 H/ 13 C Nuclear Magnetic Resonance (NMR) and Density Functional Theory (DFT) [62–64] . It was found that β ‐H transfer to aluminum and β ‐H elimination was the main chain termination pathway, while there also occurred β ‐H transfer to metal/monomer.…”

“…Over the past decades, considerable efforts have been devoted to various modifications on the bis(arylimino)pyridine‐ligand framework for improving the catalytic performance of iron complexes, including the incorporation of benzhydryl group, N‐aryl ring substituents and cyclic‐fused pyridine. These N,N,N‐tridentate iron catalysts not only have high actives and thermal stability but also yield polyethylene (PE) with a narrow molecular weight distribution [24–27] . Moreover, the N,N,N‐tridentate ligand containing iron complexes possess many advantages including: (1) the type, size and proportion of the substituents can be well controlled by adjusting the synthetic route towards the ligand design; [28] (2) The ethylene polymerization process catalyzed by the N,N,N‐tridentate ligand containing iron catalysts conforms to the Cossee‐Arlman mechanism, which makes the ethylene polymerization product highly linear; [29,30] (3) The distribution of polymerization products can be adjusted by reaction parameters such as temperature, pressure, cocatalyst, etc [31–35] .…”

“…These N,N,N-tridentate iron catalysts not only have high actives and thermal stability but also yield polyethylene (PE) with a narrow molecular weight distribution. [24][25][26][27] Moreover, the N,N,N-tridentate ligand containing iron complexes possess many advantages including: (1) the type, size and proportion of the substituents can be well controlled by adjusting the synthetic route towards the ligand design; [28] (2) The ethylene polymerization process catalyzed by the N,N,Ntridentate ligand containing iron catalysts conforms to the Cossee-Arlman mechanism, which makes the ethylene polymerization product highly linear; [29,30] (3) The distribution of polymerization products can be adjusted by reaction parameters such as temperature, pressure, cocatalyst, etc. [31][32][33][34][35] Therefore, large-scale industrial production of N,N,N-tridentate ligand iron catalysts is imminent, and their commercial application would be expected in the fields of ethylene polymerization.…”