Ethylaluminum Sesquichloride Research Articles

1,3-Butadiene Polymerizations Catalyzed by Cobalt and Iron Dichloride Complexes Bearing Pyrazolylimine Ligands

A series of pyrazolylimine ligated Co(II) and Fe(II) complexes with general formula of (PhC=N(C6H3(R1)2-2,6)(C3HN2 (R2)2-3,5)MtCl2 (R1 = Me, R2 = H, Mt = Co (1a), Fe (2a); R1 = Me, R2 = Me, Mt = Co (1b), Fe (2b); R1 = iPr, R2 = H, Mt = Co (1c), Fe (2c); R1 = iPr, R2 = Me, Mt = Co (1d), Fe (2d); R1 = iPr, R2 = Ph, Mt = Co (1e), Fe (2e)) were synthesized and thoroughly characterized. Determined by single crystal X-ray diffraction, complexes 1b and 2b revealed dimeric structures, in which distorted trigonal bipyramid geometries were adopted for each metal centers. In the presence of ethylaluminum sesquichloride (EASC), all the cobalt complexes displayed high activities in 1,3-butadiene polymerization, affording polybutadienes with predominant cis-1,4 contents (up to 97.0%). Influences of ligand structure and polymerization parameters on catalytic performance were investigated systematically. For pyrazolylimine iron(II) dichloride complexes, the catalytic activities and microstructures of the resultant polybutadienes were highly dependent on ligand structures and polymerization conditions. For complex 2a, changing cocatalyst from trialkyl aluminums to methyl aluminoxane (MAO) led to an shift of selectivity from high cis-1,4- to trans-1,4-/1,2- manner. Being activated by MAO, complexes 2a and 2b gave trans-1,4-/1,2- binary polybutadienes, while complexes 2c, 2d, and 2e afforded cis-1,4- enriched polymers.

Highly branched and high‐molecular‐weight polyethylenes produced by 1‐[2,6‐bis(bis(4‐fluorophenyl)methyl)‐4‐MeOC6H2N]‐2‐aryliminoacenaphthylnickel(II) halides

ABSTRACTA series of unsymmetrical 1‐[2,6‐bis(bis(4‐fluorophenyl)methyl)‐4‐MeOC6H2N]‐2‐aryliminoacenaphthene‐nickel(II) halides has been synthesized and fully characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance (1H NMR), 13C NMR, and 19F NMR spectroscopy as well as elemental analysis. The structures of Ni1 and Ni6 have been confirmed by the single‐crystal X‐ray diffraction. On activation with cocatalysts either ethylaluminum sesquichloride or methylaluminoxane, all the title nickel complexes display high activities toward ethylene polymerization up to 16.14 × 106 g polyethylene (PE) mol−1(Ni) h−1 at 30 °C, affording PEs with both high branches (up to 103 branches/1000 carbons) and molecular weight (1.12 × 106 g mol−1) as well as narrow molecular weight distribution. High branching content of PE can be confirmed by high temperature 13C NMR spectroscopy and differential scanning calorimetry. In addition, the PE exhibited remarkable property of thermoplastic elastomers (TPEs) with high tensile strength (σb = 21.7 MPa) and elongation at break (εb = 937%) as well as elastic recovery (up to 85%), indicating a better alternative to commercial TPEs. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 130–145

Finely tuned nickel complexes as highly active catalysts affording branched polyethylene of high molecular weight: 1-(2,6-Dibenzhydryl-4- methoxyphenylimino)-2-(arylimino)acenaphthylenenickel halides

A series of unsymmetrical 1,2-bis(imino)acenaphthenenickel(II) halides containing N-2,6-dibenzhydryl-4-methoxyphenyl – a single bulky group with adjusted electron donating properties – has been synthesized and characterized. These compounds adopt distorted tetrahedral geometry and their 1H NMR spectra show the paramagnetically shifted peaks. On activation with a low amount of Et2AlCl or ethylaluminum sesquichloride (EASC), these nickel complexes display high activity in ethylene polymerization, yielding the polyethylene of high molecular weight. They are also stable at elevated temperature; superb activity of 2.51 × 106 g of PE (mol of Ni)−1 h−1 can be attained at 90 °C. The resultant polyethylene exhibits remarkable tensile strength of 24.5 MPa and high elongation at break (602.2%) as well as substantial elastic recovery.

Synthesis of stereoblock polybutadiene possessing cis-1,4 and syndiotactic-1,2 segments by imino-pyridine cobalt complex-based catalyst through one-pot polymerization process

The iminopyridylcobalt complexes Co1-Co5 bearing bulky phenethyl or benzhydryl substituents were synthesized. Determined by single crystal X-ray crystallographic analysis, complexes Co3 and Co4 displayed tetrahedron geometries. The present complexes displayed high cis-1,4 selectivity for 1,3-butadiene polymerization upon activation with ethylaluminum sesquichloride (EASC). While upon activation with either methylaluminoxane (MAO) or trialkylaluminum-free MAO (dMAO) cocatalyst, these complexes exhibited moderate activities, addition of PPh3 into the catalyst system resulted in the increase in catalytic activities and the change of the selectivity from cis-1,4 to 1,2 manner. Moreover, the livingness of Co4/dMAO system enabled synthesis of cis-1,4-b-syn-1,2 stereodiblock polybutadiene with PPh3 as a selectivity regulating agent in one-pot polymerization process. Crystallization of syn-1,2 block and attendant expulsion of cis-1,4 block from the crystalline structure led to micro-phase separation in this stereoblock polymer.

Mono‐ and binuclear nickel catalysts for 1‐hexene polymerization

Polymerization of 1‐hexene was carried out using a mononuclear (MN) catalyst and two binuclear (BN1 and BN2) α‐diimine Ni‐based catalysts synthesized under controlled conditions. Ethylaluminium sesquichloride (EASC) was used as an efficient activator under various polymerization conditions. The highly active BN2 catalyst (2372 g poly(1‐hexene) (PH) mmol−1 cat) in comparison to BN1 (920 g PH mmol−1 cat) and the MN catalyst (819 g PH mmol−1 cat) resulted in the highest viscosity‐average molecular weight (Mv) of polymer. Moreover, the molecular weight distribution (MWD) of PH obtained using BN2/EASC was slightly broader than those obtained using BN1 and MN (2.46 for BN2 versus 2.30 and 1.96 for BN1 and MN, respectively). These results, along with the highest extent of chain walking for BN2, were attributed to steric, nuclearity and electronic effects of the catalyst structures which could control the catalyst behaviour. Differential scanning calorimetry showed that the glass transition temperatures of polymers were in the range − 58 to −81 °C, and broad melting peaks below and above 0 °C were also observed. In addition, longer α‐olefins (1‐octene and 1‐decene) were polymerized and characterized, for which higher yield, conversion and molecular weight were observed with a narrower MWD. The polymerization parameters such as polymerization time and polymerization temperature showed a significant influence on the productivity of the catalysts and Mv of samples.

Mono- and Binuclear Cobalt(II) Complexes Supported by Quinoline-2-imidate Ligands: Synthesis, Characterization, and 1,3-Butadiene Polymerization

A series of mono- and binuclear Co(II) complexes (Co1–Co7) supported by quinoline-2-imidate ligands were synthesized and thoroughly characterized. Measured by single crystal X-ray crystallography, complexes Co1 and Co3 adopted distorted tetrahedral structures around the cobalt center. Upon activation by ethylaluminium sesquichloride (EASC), these cobalt complexes exhibited high catalytic activity and cis-1,4-selectivity towards 1,3-butadiene polymerization. The effects of ligand environment, polymerization temperature, and cocatalyst types on the polymerization were investigated in detail. Interestingly, the binuclear Co(II) complexes exhibited high thermal stability, and the polymer yields were up to 97.2% even at a high temperature of 70 °C.

Cobalt (II) complexes bearing N , N , S tridentate ligands as precatalysts for 1,3-butadiene polymerization

Abstract A series of cobalt(II) complexes supported by 8-(methylthio)-2-(R-pyrazolyl)quinoline (R = H, CH3, and Ph) ligands (3a–3e) were synthesized and characterized by elemental, FT-IR, and UV–visible analyses. X-ray diffraction analysis revealed that complexes 3b and 3c adopted distorted square pyramidal geometry and trigonal bipyramidal geometry, respectively. Activated by methylaluminoxane (MAO) and ethylaluminum sesquichloride (EASC), the polymerization of 1,3-butadiene with these complexes afforded polymers with high cis-1,4 regularity (ca. 95%) in high yields. The substituent structure on the ligand influenced the catalytic behaviors. Complex 3a without substituent exhibited higher activity than its methyl-substituted counterparts 3b and 3c, while the phenyl-substituted complexes gave polymers in quantitative yields. In particular, even at a high temperature of 100 °C MAO- and EASC- based systems gave polymers in relatively high yields, indicating high thermal stability of the generated active species.

Polyethylene-Waste Tire Dust Composites Via In Situ Polymerization

Polyethylene/waste tire dust (WTD) composites were obtained by an in situ polymerization technique. The surface of the WTD was modified with deposition of polyethylene by using plasma polymerization. Ethylene polymerization was carried out using bis(cyclopentadienyl) titanium dichloride (Cp2TiCl2) as homogeneous metallocene catalyst, while diethylaluminum chloride (DEAC), ethylaluminum sesquichloride (EASC) and methyl aluminoxane (MAO) were used as co-catalysts at two different [Al]/[Ti] molar ratio. The main characteristics of the obtained polyethylenes were determined by size exclusion chromatography, thermogravimetric analysis, differential scanning calorimetry and wide-angle X-ray diffraction. The results showed that by using EASC and MAO the highest catalytic activities were presented at a [Al]/[Ti] molar ratio of 9.17 and 18.33 respectively. Even though it was possible to obtain polyethylene using WTD (modified or unmodified) the catalytic activity was lower than in the case in which no WTD was added in ethylene polymerization. Scanning transmission electronic microscopy images evidenced that the original morphology of the polyethylenes was not modified by the presence of WTD.

Alkyl‐Branched Fatty Compounds: Hydro‐Alkylation of Non‐Activated Alkenes With Haloalkanes Mediated by Ethylaluminum Sesquichloride

The general method for the cationic hydro‐alkyl addition to the nonactivated CC double bond of alkenes mediated by ethylaluminum sesquichloride (Et3Al2Cl3) has been importantly improved and simplified by using haloalkanes (primary, secondary, tertiary) instead of alkyl chloroformates as alkylating agent and performing the reaction without any additional solvent. The protocol is especially suited to perform the hydro‐alkylation of internal double bonds. Reaction of the haloalkane with Et3Al2Cl3 gives an alkyl cation which is added to the alkene; hydride transfer from Et3Al2Cl3 to the adduct carbenium ion gives the saturated addition product. Primary halo alkanes give the same addition product as the respective secondary halo alkane because of 1,2‐H shift yielding the secondary carbenium ions. In the case of 1‐alkenes triethylsilane has to be used as additional hydride donor to avoid di‐ and oligomerization. Special interest has been focused on alkylation of unsaturated fatty compounds, which are important renewable feedstocks, mostly (Z)‐configured such as methyl oleate, high oleic sunflower oil, neopentyl glycol dioleate, but also (E)‐configured, that is, dimethyl (E)‐icos‐10‐enedioate, and with terminal double bond such as methyl 10‐undecenoate. The respective alkyl branched fatty compounds were obtained after simple work‐up with excellent to good yields. The protocol was scaled up without problems to >0.5 mol.Practical Applications: The synthesis of alkyl‐branched fatty compounds is of high importance since they have interesting properties that make them attractive for use in the cosmetics and lubricant area. We developed an industrially feasible method for the synthesis of well‐defined alkyl branched oleochemicals.The ethylaluminum sesquichloride (Et3Al2Cl3)‐mediated reaction of non‐activated alkenes with haloalkanes gives the respective hydro alkylation product in excellent to good yields. The reaction protocol allows the synthesis of well‐defined alkyl branched oleochemicals, as for example methyl 9(10)‐isopropylstearate, and can easily be scaled up.

2-Chloro/phenyl-7-arylimino-6,6-dimethylcyclopenta[b]pyridylnickel chlorides: Synthesis, characterization and ethylene oligomerization

2-Chloro/phenyl-7-arylimino-6,6-dimethylcyclopenta[b]pyridylnickel chlorides (Ni1–Ni8) were synthesized from the respective ligands L1–L8 and characterized. Upon activation with either methylaluminoxane (MAO) or ethylaluminium sesquichloride (EASC), they show high catalytic activity of up to 10.84×106g(oligomer) mol−1(Ni) h−1 in ethylene oligomerization. The products range from butenes to dodecenes for Ni1–Ni4, but are limited to butenes and hexenes in the case of Ni5–Ni8. DFT calculations indicate that the NiC bond length in the model alkyl complexes depends both on the nature of the substituents at the heterocycles and the kind of the alkyl group, shedding some light on the preferences of the precatalysts toward oligomers or polyethylene.

Cobalt-β-diimine complexes for ethylene oligomerization

This work describes the synthesis of cobalt-β-diimine complexes as well as their application as ethylene oligomerization catalyst precursors. The ligands differ from each other by substituents on the aromatic rings. The catalytic precursors were tested in ethylene oligomerization, using EASC (Ethylaluminium sesquichloride, Et2Al2Cl3) as co-catalyst, and toluene as solvent and displayed TOF in the range of 0.8 to 34s−1. The catalytic systems were selective in the C4-C6 fraction, attaining 100% selectivity in C4. It was observed that the ligands nature strongly influence the catalytic activity.

Use of Vanadium Complexes Bearing Naphthalene-Bridged Nitrogen-Sulfonate Ligands as Catalysts for Copolymerization of Ethylene and Propylene.

Vanadium complexes bearing naphthalene-bridged nitrogen-sulfonate ligand ([ê2(N,O)-8-(PhN)-1-naphthalenesulfonato]VOCl (1a) and [ê2(N,O)-8-(PhN)-1-naphthalenesulfonato]VCl2 (1b)) were synthesized. Activated by ethylaluminium sesquichloride (EASC) and in the presence of ethyl trichloroacetate (ETCA) as reactivator, complexes 1a and 1b showed activities of up to 39.1 kg polymer (mol V)−1 h−1, affording the copolymers with high molecular weights (Mw up to 28 × 104) and narrow molecular weight distributions (Mw/Mn ~ 3.0) as well as high propylene incorporation of up to 49.4%. Compared to the traditional VOCl3 system, these complexes exhibited higher propylene incorporation ability and higher catalytic activities especially at high polymerization temperatures of 50 °C and above. Determined by DSC and 13C NMR, the copolymers obtained with 1a and 1b had more random structures than that with the VOCl3 system.

N-(2,2-Dimethyl-1-(quinolin-2-yl)propylidene) arylaminonickel Complexes and Their Ethylene Oligomerization.

A series of N-(2,2-dimethyl-1-(quinolin-2-yl)propylidene) arylamines was sophisticatedly synthesized and reacted with nickel(II) bromine for the formation of the corresponding nickel complexes. All the organic compounds were characterized by IR, NMR spectra and elemental analysis, while all the nickel complexes were characterized by IR spectra and elemental analysis. On activation with ethylaluminium sesquichloride (EASC) and modified methylaluminoxane (MMAO), all nickel precatalysts exhibited good activities toward ethylene oligomerization, indicating the positive efficiency of gem-dimethyl substitutents; in which major hexenes were obtained with MMAO. The catalytic parameters were verified, and the steric and electronic influences of substituents with ligands were observed, with a slight change of activities under different ethylene pressures.

β-Diimine nickel complexes in BMI·AlCl4 ionic liquid: a catalytic biphasic system for propylene oligomerization

β-Diimine nickel complexes have been synthesized using phenyl-amino-based ligands (NPh) substituted with none, two or three methyl groups. The resulting complexes, NiNPh, NiNPhMe2 and NiNPhMe3, which associated with ethylaluminum sesquichloride (EASC) as a co-catalyst, were tested for propylene oligomerization conducted under homogeneous and biphasic conditions using cyclohexane and the ionic liquid 1-methyl-3-butylimidazolium tetrachloroaluminate (BMI·AlCl4), respectively. The cocatalyst/nickel complex ratio was evaluated (Al/Ni=100 and 200) for both systems. Under homogeneous conditions, the highest activity was obtained with NiNPh and Al/Ni=100 (9s−1), and the highest selectivity in propylene dimers was attained with NiNPhMe3 (91%). Under biphasic conditions, all the catalysts showed activities similar or slightly superior to those obtained under homogeneous conditions; the highest activity was attained with NiNPh (10.8s−1), and the highest selectivity for propylene dimers was attained with NiNPhMe3 (98.3%). Under both reaction conditions, i.e., homogeneous and biphasic, 2-methyl-2-pentene was the major product. However, when reactions were conducted under biphasic conditions, less products were formed by isomerization in comparison with those formed using homogeneous systems. For the recycling reactions, no significant changes in the activity of the system were observed for each new cycle.

Synthesis and application of bidentate nickel complexes bearing hyperbranched salicylaldimine ligands in ethylene oligomerization

Three bidentate salicylaldimine nickel complexes containing different long-chain alkyl groups in their ligand backbone were synthesized in good yield. All the bidentate salicylaldimine ligands and their nickel complexes were fully characterized by FT-IR, 1H NMR, UV spectroscopies, and mass spectrometry. Three bidentate nickel complexes were evaluated as catalyst precursors in ethylene oligomerization. Upon activation with methylaluminoxane (MAO), the catalytic activity was 5.75 × 105 g/(mol Ni·h) and the oligomers were mainly butenes (52.10%) and octenes (32.63%) for bidentate nickel complex with 1-tetradecyl as core in the ligand backbone (R14-complex) using toluene as solvent. However, bidentate nickel complex with 1-octadecyl as core in the ligand backbone (R18-complex) produced mainly octenes (59.38%) and C10 + olefins (29.01%) and the catalytic activity was 2.23 × 105 g/(mol Ni·h). After activation with ethylaluminum sesquichloride (EASC) in toluene, three nickel complexes yielded mainly C10 + products which contained Friedel-Craft alkylated-toluene, and their catalytic activities were above 1.5 × 106 g/(mol Ni·h). For the bidentate salicylaldimine nickel catalysts with hyperbranched molecules as ligand backbones, the solvent and the reaction conditions had a large effect on catalytic activity as well as oligomerization distribution except the structure of the catalyst and the co-catalyst.

Synthesis, characterization, and ethylene oligomerization of three novel dendritic nickel catalysts

Three dendritic nickel complexes C1–C3 were synthesized from three poly(amido amine) dendrimers, salicylic aldehyde and nickel chloride hexahydrate via Schiff base condensation reaction and coordination reaction. The structures of the dendritic ligands and nickel complexes were characterized by FT-IR, UV, 1H NMR, ESI–MS, and elemental analysis. When activated with aluminum co-catalysts, three complexes C1–C3 were able to catalyze ethylene oligomerization. The catalytic activities and the product distribution of complexes C1–C3 were depended on the reaction parameter, co-catalyst, solvent, and the structure of the pre-catalyst. When using ethyl aluminum sesquichloride (EASC) as co-catalyst in toluene, the catalytic activity of complex C3 containing the longest bridging methylene groups reached the highest value of 1.63 × 106 g·(mol Ni·h)−1 with 69.15% C11 in the product at 30 min, 25 °C, 0.5 MPa, and Al/Ni ratio of 900.

Synthesis and Characterization of Polyethylene/Starch Nanocomposites: A Spherical Starch-Supported Catalyst and In Situ Ethylene Polymerization.

In the present article, a novel spherical starch-supported vanadium (V)-based Ziegler-Natta catalyst was synthesized. The active centers of the obtained catalyst well dispersed in the starch through the SEM-EDX analysis. The effects of reaction conditions on ethylene polymerization were studied. The synthesized catalyst exhibited high activity toward ethylene polymerization in the presence of ethylaluminium sesquichloride (EASC) cocatalyst. Interestingly, the fiber shape PE was obtained directly during the polymerization process.

Cobalt complexes based on dendritic PAMAM bridged salicylaldimine ligands: Synthesis, characterization and performance in ethylene oligomerization

ABSTRACTTwo novel dendritic poly(amido-amine) (PAMAM) bridged salicylaldimine ligands were synthesized by Schiff base reaction using 1.0 generation dendritic PAMAM as bridged groups. The cobalt complex with 1,4-butanediamine as core (C1) and the cobalt complex with 1,6-hexanediamine as core (C2) based on dendritic PAMAM bridged salicylaldimine ligands were prepared by metallic coordination reaction, respectively. The structures of the ligands and the dendritic cobalt complexes were characterized by fourier transform infrared (FTIR), ultraviolet spectra (UV), hydrogen nuclear magnetic resonance (1H NMR) and electrospray ionization mass spectra (ESI-MS). The complexes C1 and C2 were evaluated as catalyst precursors for ethylene oligomerization after being activated with methylaluminoxane (MAO), diethylaluminum chloride (Et2AlCl), ethylaluminium dichloride (EtAlCl2) and ethylaluminum sesquichloride (EASC). The dendritic cobalt complexes exhibited the highest activity and selectivity for high carbon oligomers with EASC as activator. Under the conditions of 1.0 MPa, 25°C and Al/Co molar ratio 1500, the catalytic activity and selectivity for C10–C20 using C1 were 3.44×106 g·(mol Co·h)−1 and 76.53% after activation with EASC, and the catalytic activity and selectivity for C10–C20 using C2 were 3.42×106 g·(mol Co·h)−1 and 84.50%, respectively.

Novel nickel complexes with hyperbranched structure: Synthesis, characterization and performance in ethylene oligomerization

Two novel nickel complexes with hyperbranched structure were synthesized with 1.0 generation hyperbranched polyamine molecules (1.0G), salicylaldehyde and anhydrous nickel chloride as materials via the Schiff’s base and the complexation reactions. The structures of the novel hyperbranched ligands and their nickel complexes were characterized by FT-IR, 1H NMR, UV, ESI-MS and elemental analysis. The hyperbranched nickel complexes were evaluated as catalyst precursors for ethylene oligomerization after being activated with methylaluminoxane (MAO), diethylaluminum chloride (Et2AlCl) and ethylaluminum sesquichloride (EASC). The influence of Al/Ni ratio, temperature and ethylene pressure on ethylene oligomerization was also investigated using the novel hyperbranched nickel complexes as pre-catalysts and MAO as co-catalyst. The catalytic activities of the two hyperbranched nickel complexes with dodecyl and octadecyl as cores (R12-complex and R18-complex) were 2.33×105g/(mol Ni·h) and 1.23×105g/(mol Ni·h), respectively, and the selectivities for C8+ oligomers of R12-complex and R18-complex were 56.16% and 88.64% respectively, when the Al/Ni molar ratio was 500:1, the temperature was 25°C, the pressure of ethylene was 0.5MPa and the co-catalyst was MAO. The catalytic activities and product distribution were largely dependent on the nature of the co-catalysts and the structures of nickel complexes. The catalytic activities decreased with increasing of the length of alkyl chain of the hyperbranched nickel complexes.

Polymerization of 1,3-butadiene catalyzed by cobalt(II) and nickel(II) complexes bearing pyridine-2-imidate ligands

Cobalt and nickel complexes (1a-1d and 2a-2d, respectively) supported by 2-imidate-pyridine ligands were synthesized and used for 1,3-butadiene polymerization. The complexes were characterized by IR and element analysis, and complex 1a was further characterized by single-crystal X-ray diffraction. The solid state structure of complex 1a displayed a distorted tetrahedral geometry. Upon activation with ethylaluminum sesquichloride (EASC), all the complexes showed high activities toward 1,3-butadiene polymerization. The cobalt complexes produced polymers with high cis-1,4 contents and high molecular weights, while the nickel complexes displayed low cis-1,4 selectivity and the resulting polymers had low molecular weights. The catalytic activities of the complexes highly depended on the ligand structure. With the increment of polymerization temperature, the cis-1,4 content and the molecular weight of the resulting polymer decreased.