Ethylene oligomerization studies by nickel(ii) complexes chelated by (amino)pyridine ligands: experimental and density functional theory studies

Abstract

Reductions of imine compounds 2-methoxy-N-(1-(pyridin-2-yl)ethylidene)ethanamine (L1), 2-methoxy-N-((pyridin-2-yl)methylene)ethanamine (L2), N,N-diethyl-N-((pyridin-2-yl)methylene)ethane-1,2-diamine (L3) and 2-((pyridin-2-yl)methyleneamino)ethanol (L4) using NABH4 produced their corresponding amine analogues N-(2-methoxyethyl)-1-(pyridin-2-yl)ethanamine (L1a), 2-methoxy-N-((pyridin-2-yl)methyl)-ethanamine (L2a), N,N-diethyl-N-((pyridin-2-yl)methyl)ethane-1,2-diamine (L3a) and 2-((pyridin-2-yl)methylamino)ethanol (L4a) in good yields. Reactions of the (amino)pyridine ligands L1a–L4a with [NiBr2(DME)] afforded nickel(II) complexes, [NiBr2(L1a)2] (1), [NiBr2(L2a)2] (2), [NiBr2(L3a)2] (3) and [NiBr2(L4a)2] (4), respectively in quantitative yields. Molecular structures of complexes 2 and 4 confirmed the formation of the bis(chelated)nickel(II) complexes. Activation of complexes 1–4 with either EtAlCl2 or methylaluminoxane (MAO), produced active ethylene oligomerization catalysts to afford mostly ethylene dimers (C4), in addition to trimmers (C6) and tetramers (C8). Density functional theory studies provided valuable insight into the reactivity trends and influence of complex structure on the ethylene oligomerization reactions.

Synthesis and characterization of (pyrazolylethylphosphinite)nickel(II) complexes and catalytic activity towards ethylene oligomerization

“…Pre‐catalyst 5 recorded the highest catalytic activity and was therefore used to determine the optimum reaction conditions of temperature, time, ethylene pressure (Table ) and Ni:Al ratio. The product distribution observed is similar to what was reported in earlier studies . After analyzing the catalytic products with GC (Figure S2–S4), all the volatiles were pumped off, leaving an oily product which was characterized by 1 H–NMR, Atmospheric Pressure Chemical Ionization (APCI) technique and 2D–GC as shown in Figure S5–S7.…”

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

“…27) [118]. Upon activation with either EtAlCl2 or MAO, 49 exhibited a high catalytic activity of 2.74× 10 6 g oligomer mol −1 (Ni) h −1 and produced mostly ethylene dimers (C4), in addition to some trimers (C6) and tetramers (C8) [118].…”

Straightforward Design for Phenoxy-Imine Catalytic Activity in Ethylene Polymerization: Theoretical Prediction

“…As an inexpensive material, polyethylene (PE) has drawn significant attention due to its excellent physical properties, such as high mechanical strength, high elasticity and high resistivity towards corrosion, light weightness, and reusability [1][2][3][4]. Normally, the polyethylene materials are prepared via the coordination polymerization using different categories of catalysts, among which metallocenes are very promising candidates that provide high activity and selectivity [5][6][7][8][9][10][11].…”

“…Therefore, nowadays, many researchers aim to develop efficient catalysts through ligand design and functionality modification [25][26][27][28][29]. In addition, the metal center was also investigated by substitution between early transition metals and late transition metals, such as Ti and Ni, respectively [2,5,30,31].…”