Ethylene Polymerization Behavior Research Articles

Synthesis, structural characterization, and ethylene polymerization behavior of (arylimido)vanadium(V) complexes bearing tridentate Schiff base ligands

A series of novel (arylimido)vanadium(V) complexes bearing tridentate salicylaldiminato chelating ligands, V(N-2,6-Me2C6H3)Cl2[(O-2-tBu-4-R-C6H3)CHND] (R = H, D = 2-CH3OC6H4 (2a); 2-CH3SC6H4 (2b); 2-Ph2PC6H4 (2c); 8-C9H6N (quinoline) (2d); CH2C5H4N (2e); R = tBu, D = 2-Ph2PC6H4 (2f)), were prepared from V(NAr)Cl3 by reacting with 1.0 equiv of the ligands in the presence of triethylamine in tetrahydrofuran. These complexes were characterized by 1H, 13C, 31P, and 51V NMR spectra and elemental analysis. The structures of 2c and 2f were further confirmed by X-ray crystallographic analysis. These (arylimido)vanadium(V) complexes are effective catalyst precursors for ethylene polymerization in the presence of Et2AlCl as a cocatalyst and ethyl trichloroacetate as a reactivating agent. Complex 2c with a PPh2 group in the sidearm was found to exhibit an exceptional activity up to 133800 kg polyethylene/molV h for ethylene polymerization at 75 °C, which is one of the highest activities displayed by homogeneous vanadium(V) catalysts at high temperature. Moreover, high molecular weight polymers with unimodal molecular weight distribution can be obtained, indicating the single site behavior of these catalysts. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2633-2642

Ethylene polymerization with novel phenoxy-imine catalysts bearing 4-vinylphenyl group

This contribution reports ethylene polymerization behavior of titanium complexes incorporating bis(phenoxyimine) ligands. Six phenoxy-imine Ti(IV) complexes {6-R1-2-[CH=N(2,6-difluoro-3,5-diR2-4-R3Ph)]C6H3O}2TiCl2 (1: R1 = H, R2 = H, R3 = H; 2: R1 = H, R2 = H, R3 = 4-vinylphenyl; 3: R1 = CH3, R2 = H, R3 = H; 4: R1 = CH3, R2 = H, R3 = 4-vinylphenyl; 5: R1 = CH3, R2 = F, R3 = H; 6: R1 = CH3, R2 = F, R3 = 4-vinylphenyl) have been synthesized and evaluated for ethylene polymerization using dried MAO (simplified as DMAO) as cocatalyst. An obvious catalytic heterogeneity of Cat 2 (Complex 2/DMAO) towards ethylene polymerization was observed, which was illustrated by decreased activity, multimodal molecular weight distribution and partially improved particle morphology comparing with Cat 1. Moreover, Cat 3 exhibits “living” characteristics in the process under certain conditions (25 °C, less than 20 min). Otherwise, the moderate to high ethylene polymerization activity of ca. 105–106 g PE/(mol Ti·h) and high molecular weight (Mw = 105–106) of polyethylene can be obtained by changing the skeleton structure of these complexes.

2‐(1‐(2,4‐Bis((di(4‐fluorophenyl)methyl)‐6‐methylphenylimino)ethyl)‐6‐(1‐(arylimino)ethyl)pyridylmetal (iron or cobalt) Complexes: Synthesis, Characterization, and Ethylene Polymerization Behavior

A series of 2‐(1‐(2,4‐bis((di(4‐fluorophenyl)methyl)‐6‐methylphenylimino)ethyl)‐6‐(1‐(aryl­imino)ethyl)pyridines is synthesized and used to form their corresponding iron(II) and cobalt(II) chloride complexes thereof. All the organic compounds are fully characterized by elemental analysis, and IR and 1H/13C NMR spectroscopy, whereas the corresponding iron and cobalt complexes are characterized by elemental analysis and IR spectroscopy, as well as single‐crystal crystallography for the Fe2, Co1, and Co2 complexes, revealing a distorted trigonal bipyramidal structure. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the iron complexes exhibit high activities toward ethylene polymerization at 60 °C; meanwhile, all the cobalt analogs demonstrate slightly lower activities at the optimized temperatures of 60 °C (MAO as cocatalyst) or 70 °C (MMAO as cocatalyst). All the polyethylenes obtained from cobalt precatalysts possess narrow polydispersity and lower molecular weights than those from their iron analogs. image

Grafting of the zirconium complexes [Zr(η5-C5H5){NC-amidine}Cl2] and [Zr(η5-C5H5)(NC-NacNac)Cl2] and the study of their behavior in ethylene polymerization

The synthesis of the new zirconium complex [Zr(η5-C5H5){NC-amidine}Cl2] (1) has been achieved by reaction of the amidine (E)-N-(4-cyanophenyl)-N′-(2,6-diisopropylphenyl)acetimidamide with [Zr(η5-C5H5)Cl3] and the new complex has been characterized by spectroscopic methods. The reaction of one equivalent of B(C6F5)3 with compound 1 produces the adduct [Zr(η5-C5H5){(C6F5)3B-NC-amidine}]Cl2 (2). Complexes 1 and 2 have been tested as homogeneous catalysts in olefin polymerization using MAO as cocatalyst.The grafting of 1 and the previously reported complex [Zr(η5-C5H5)(NC-NacNac)Cl2] (3) on to several inorganic solid supports, namely dehydroxylated silica (SiO2(TEMP)) (S1), dehydroxylated silica modified with O(SiMe3)2 (S2) or MAO (S3), and MgCl2 (S4) has been carried out by addition of a freshly prepared solution of 1 or 3 to the corresponding inorganic solid. FT-IR studies of the new materials showed that the links between complexes 1 or 3 and S1 and S2 occur through the zirconium center, whereas with S3 and S4 the links involve the CN functional group of the ligand. These new materials have been studied as catalysts in olefin polymerization reactions in the presence of MAO. A UV–vis study was carried out in order to identify the minimum amount of MAO necessary to produce the active species. A preliminary study into the activity in olefin polymerizations was also carried out.

Ruthenium(IV) Complexes for Ethylene Insertion Polymerization

The synthesis, characterization, and ethylene polymerization behavior of novel RuIV(η3:η3-C10H16)(OPO) (OPO = bis(arenesulfonato)phosphine) complexes is reported here. Upon activation with AlMe3-depleted methylaluminoxane (dMAO), the Ru(IV) precursors were able to produce polyethylene with activities up to 1182 h–1 turnover frequency (TOF). The polymers were highly linear with a low degree of branching (<12 methyl branches per 1000 C) and had high molecular weights (up to Mp = 289 kg mol–1) with a bimodal molecular weight distribution. The polymerization activity increased with decreasing donor strength of the OPO ligand.

Biphenyl-Bridged 6-(1-Aryliminoethyl)-2-iminopyridylcobalt Complexes: Synthesis, Characterization, and Ethylene Polymerization Behavior

A series of biphenyl-bridged 6-(1-aryliminoethyl)-2-iminopyridine derivatives reacted with cobalt dichloride in dichloromethane/ethanol to afford the corresponding binuclear cobalt complexes. The cobalt complexes were characterized by FT-IR spectroscopy and elemental analysis, and the structure of a representative complex was confirmed by single-crystal X-ray diffraction. Upon activation with either MAO or MMAO, these cobalt complexes performed with high activities of up to 1.2 × 107 g (mol of Co)−1 h–1 in ethylene polymerization, which represents one of the most active cobalt-based catalytic systems in ethylene reactivity. These biphenyl-bridged bis(imino)pyridylcobalt precatalysts exhibited higher activities than did their mononuclear bis(imino)pyridylcobalt precatalyst counterparts, and more importantly, the binuclear precatalysts revealed a better thermal stability and longer lifetimes. The polyethylenes obtained were characterized by GPC, DSC, and high-temperature NMR spectroscopy and mostly possessed unimodal and highly linear features.

2-(1-(2-Benzhydrylnaphthylimino)ethyl)pyridylnickel halides: synthesis, characterization, and ethylene polymerization behavior

A series of 2-(1-(2-benzhydrylnaphthylimino)ethyl)pyridine derivatives (L1-L3) was synthesized and fully characterized. The organic compounds acted as bi-dentate ligands on reacting with nickel halides to afford two kinds of nickel complexes, either mononuclear bis-ligated L2NiBr2 (Ni1-Ni3) or chloro-bridged dinuclear L2Ni2Cl4 (Ni4-Ni6) complexes. The nickel complexes were fully characterized, and the single crystal X-ray diffraction revealed for Ni2, a distorted square pyramidal geometry at nickel comprising four nitrogens of two ligands and one bromide; whereas for Ni4, a centrosymmetric dimer possessing a distorted octahedral geometry at nickel was formed by two nitrogens of one ligand, two bridging chlorides and one terminal chloride along with oxygen from methanol (solvent). When activated with diethylaluminium chloride (Et2AlCl), all nickel complexes performed with high activities (up to 1.22 × 10(7) g (PE) mol(-1) (Ni) h(-1)) towards ethylene polymerization; the obtained polyethylene possessed high branching, low molecular weight and narrow polydispersity, suggestive of a single-site active species. The effect of the polymerization parameters, including the nature of the ligands/halides on the catalytic performance is discussed.

Half-titanocene 5-t-butyl-2-(1-(arylimino)methyl)quinolin-8-olate chlorides: Synthesis, characterization and ethylene (co-)polymerization behavior

A series of half-titanocene chloride complexes bearing 5-t-butyl-2-(1-(arylimino)methyl)quinolin-8-olate ligands (L), CpTiLCl2, has been synthesized in acceptable yields by the stoichiometric reaction of CpTiCl3 with the respective potassium 5-t-butyl-2-(1-(arylimino)methyl)quinolin-8-olate. All half-titanocene complexes were fully characterized by elemental analysis and NMR spectroscopy, and the molecular structures of the representative complexes C1 and C2 were confirmed as pseudo octahedral at titanium by single-crystal X-ray diffraction. When activated with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all titanium complexes exhibited good activities (up to 4.8 × 105 g mol−1(Ti) h−1) towards ethylene polymerization. The obtained polyethylene exhibited ultra-high molecular weight (up to 11.82 × 105 g mol−1) with narrow polydispersity. Furthermore, effective co-polymerization of ethylene with 1-hexene or 1-octene was achieved with several percentages of co-monomer incorporation in the resultant polyethylenes.

Highly Thermally Stable Eight-Coordinate Dichloride Zirconium Complexes Supported by Tridentate [ONN] Ligands: Syntheses, Characterization, and Ethylene Polymerization Behavior

A series of novel eight-coordinate dichloride zirconium complexes with the general formula L2ZrCl2 supported by two tridentate [ONN] ligands have been synthesized by the reaction of ZrCl4·2THF with 2 equiv of the corresponding ligands (tridentate phenoxy-imine ligands (L1H–L4H) or tridentate phenoxy-amine ligands (L5H and L6H)). These complexes were characterized by NMR and elemental analyses. The molecular structures of representative zirconium complexes C2 and C6 were confirmed by single-crystal X-ray diffraction and revealed that the metal center is eight-coordinated by two tridentate [ONN] ligands and two chlorides in a distorted-square-antiprismatic geometry. When C1–C6 were activated by modified methylaluminoxane (MMAO), the resultant catalysts displayed notable thermal stability and high activities toward ethylene polymerization. The ligand substituents, the metal coordination environment, and the reaction conditions had a profound effect on the polymerization. The catalytic activity increases cons...

Zirconium complexes bearing bis(phenoxy‐imine) ligands with bulky o‐bis(aryl)methyl‐substituted aniline groups: synthesis, characterization and ethylene polymerization behavior

A series of bis(phenoxy‐imine) zirconium complexes bearing bulky o‐bis(aryl)methyl‐substituted aryl groups on the aniline moiety have been synthesized, characterized and tested as catalyst precursors for ethylene polymerization. 1H NMR spectroscopy suggests that these complexes exist as a single chiral C2‐symmetric isomer in the solution. X‐ray crystallographic analysis of the resulting biszwitterionic‐type adduct complex C1 · 2HCl reveals that the phenoxy‐imine groups function as a monodentate phenoxy ligand and the oxygen atoms are oriented trans to each other at the central metal atom. Using modified methylaluminoxane (MMAO) as co‐catalyst, C1 · 2HCl, C2–C6 exclusively produce linear aluminium‐terminated polyethylenes (Al‐PEs) with high activity (up to 16.89 × 106 g PE (mol Zr h)−1, suggesting that chain transfer to aluminum is the predominant termination mechanism. It is noteworthy that the introduction of an excessively bulky o‐bis(aryl)methyl substituent adjacent to the imine‐N produces low molecular‐weight Al‐PEs (Mv 1.6–10.1 × 103) due to the enhanced rate of chain transfer to alkylaluminium groups during polymerization. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Synthesis and characterization of tridentate [O−N(H)X] titanium complexes and their applications in olefin polymerization

ABSTRACTA series of [O−N(H)X]TiCl3 complexes derived from (arylamino)methylene phenol are prepared. The molecular structures of the complexes are characterized by 1H NMR, 13C NMR, and X‐ray analysis. Upon activation with modified methylaluminoxane (MMAO), the titanium complexes display high thermal stability and single‐site like ethylene (co)polymerization behavior at the temperatures of up to 150 °C. 1‐Octene and 1‐octadencene prove suitable to be incorporated into polyethylene backbone at 110 °C and the highest activity of 1.89 × 106 g/mol(Ti)·h·atm can be achieved. The pendant group X has great influence on the catalytic behaviors of the complexes, and PPh2 proves to be the optimal group. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2495–2503

2-(1-{2,6-Bis[bis(4-fluorophenyl)methyl]-4-methylphenylimino}ethyl)-6-[1-(arylimino)ethyl]pyridylcobalt dichlorides: Synthesis, characterization and ethylene polymerization behavior

A series of 2-(1-{2,6-bis[bis(4-fluorophenyl)methyl]-4-methylphenyl-imino}ethyl)-6-[1-(arylimino)ethyl]pyridylcobalt(II) chloride complexes (Co1–Co5) was synthesized and characterized by FT-IR spectroscopy and elemental analysis. The molecular structures of the representative cobalt complexes Co1 (R1 = Me, R2 = H), Co4 (R1 = Me, R2 = Me) and Co5 (R1 = Et, R2 = Me) were determined by single crystal X-ray diffraction, and revealed a pseudo-square-pyramidal geometry at cobalt. Upon activation with either MMAO or MAO, all cobalt complex pre-catalysts exhibited high activities [up to the range of 107 g of PE (mol of Co)−1 h−1] toward ethylene polymerization. The influence of reaction parameters and the nature of the ligands were investigated in detail on the catalytic activities of the corresponding complexes and properties of the resultant polyethylene. The cobalt system revealed single-site behavior and produced polyethylene with narrow molecular distribution. Compared to the use of MAO, the use of MMAO produced polyethylene of higher molecular weight.

Synthesis, characterization and ethylene polymerization behavior of binuclear iron complexes bearing N,N′-bis(1-(6-(1-(arylimino)ethyl) pyridin-2-yl)ethylidene)benzidines

A series of N,N′-bis(1-(6-(1-(arylimino)ethyl)pyridin-2-yl)ethylidene)benzidines and the bi-metallic iron complexes thereof have been synthesized and fully characterized. All iron complexes, when activated by MAO or MMAO, exhibited high activities of up to 1.3 × 107 g mol−1 (Fe) h−1 for the polymerization of ethylene. On comparison with their mononuclear counterparts, such bi-metallic complexes not only retain a relatively high activity at elevated temperatures (up to 70 °C), but also exhibit increased lifetimes. The polyethylenes obtained were characterized by GPC, DSC and high temperature NMR spectroscopy, which indicated multimodal and highly linear features.

Effect of Al‐alkyl cocatalyst on ethylene polymerization behavior using silyl chromate (SC)/SiO2 catalyst

ABSTRACTCr/SiO2 catalysts are important industrial ethylene polymerization catalysts, mainly including Phillips catalyst (also called oxo chromium/SiO2) and silyl chromate/SiO2 systems (named as SC/SiO2, also called UCC S‐2 catalyst). Compared with Phillips catalyst, SC/SiO2 catalyst is not fully investigated. In this work, SC/SiO2 catalyst was prepared, and triethylaluminum or triisobutylaluminium was used as cocatalyst for ethylene homopolymerization. The effects of cocatalysts on polymerization kinetics and polymer microstructure were investigated. It is found that the kinetic curves using SC/SiO2 catalyst in the presence of triethylaluminum or triisobutylaluminium seem to be a hybrid type composed of two types of basic polymerization kinetics: one is a fast built‐up and fast decay type, and the other is a slow built‐up and slow decay type, which indicates the existence of two types of polymerization active sites. Plausible mechanisms of the formation and transformation of active sites were proposed to rationalize the unique polymerization behavior. © 2012 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

2-(1-(Arylimino)ethyl)-8-arylimino-5,6,7-trihydroquinoline Iron(II) Chloride Complexes: Synthesis, Characterization, and Ethylene Polymerization Behavior

The series of 2-(1-(arylimino)ethyl)-8-arylimino-5,6,7-trihydroquinolines was synthesized and fully characterized, for which data indicated two isomer forms of each due to the migration of a double bond. The corresponding iron dichloride complexes were prepared and were found to adopt distorted bipyramidal coordination geometry at iron by single-crystal X-ray diffraction studies. Upon treatment with either MAO or MMAO, all iron complex precatalysts exhibited high activities (up to 2.4 × 107 gPE·mol–1(Fe)·h–1) toward ethylene polymerization. The influence of the nature of the ligands and reaction parameters upon the catalytic activities and properties of the polyethylene obtained has been studied.

TiCl4 immobilized on a composite support SiO2/MgCl2·x(1,4-butanediol)/poly[styrene-co-(acrylic acid)] for ethylene polymerization: The barrier effect of poly[styrene-co-(acrylic acid)

By immobilizing titanium-based Ziegler–Natta catalyst on composite support, SiO2/MgCl2·x(1,4-butanediol)/poly[styrene-co-(acrylic acid)] (SiO2/MgCl2·xBD/PSA) and SiO2/MgCl2·xBD/PSA/TiCl4 (SMPT) were synthesized for ethylene polymerization. SiO2/MgCl2·xBD/TiCl4 without PSA was also prepared for comparison. The results of energy-dispersive X-ray analysis, SEM, and thermogravimetric analysis demonstrated that SMPT had a unique core-mantle-shell structure. The PSA layer can be considered as a barrier for the mass-transfer of reactants based on the results of self-diffusion measurement by pulsed field gradient NMR and ethylene polymerization. The polyethylene produced by SMPT showed high molecular weight (MW) and broad molecular weight distribution (MWD). The influences of PSA content, hydrogen, and comonomer on the ethylene polymerization behavior were also investigated. The results further demonstrated that the PSA layer in the composite support had different diffusion capabilities to the reactants. The physical properties of the produced polyethylene implied the possibility to control the MW and MWD of polyethylene by the manipulation of PSA layer. The catalyst fragmentation during ethylene polymerization was also affected by the PSA shell due to its barrier effect. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

2-[1-(2,4-Dibenzhydryl-6-methylphenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridylcobalt(ii) dichlorides: Synthesis, characterization and ethylene polymerization behavior

A series of cobalt(II) dichloride complexes ligated by 2-[1-(2,4-dibenzhydryl-6-methylphenylimino) ethyl]-6-[1-(arylimino)ethyl]pyridines was synthesized and characterized by FT-IR spectroscopy and elemental analysis. The molecular structure of the representative complex Co4 (R1 = Me, R2 = Me) was confirmed as pseudo square-pyramidal geometry at cobalt by single-crystal X-ray diffraction. Upon treatment with the co-catalysts MAO or MMAO, all cobalt pre-catalysts exhibited high activities up to 1.81 × 107 g PE mol−1(Co) h−1 in ethylene polymerization, and produced polyethylene products with molecular weights in the tens of thousands and narrow molecular weight distributions. The influence of the reaction parameters and nature of the ligands on the catalytic behavior of the title cobalt complexes was investigated.

Metal (Mg, Fe, Co, Zr and Ti) complexes derived from aminosilyl substituted aminopyridinato ligand: synthesis, structures and ethylene polymerization behaviors of the group 4 complexes

Lithium N-[(N,N-dimethylamino)dimethylsilyl]-2-pyridylamidate (2) was prepared from the reaction of new compound N-[(N,N-dimethylamino)dimethylsilyl]-2-pyridylamine (1) and LiBu(n). Treatment of the lithium salt (2) with an equal equivalent of MgBr(2)(THF)(2), FeCl(2) and CoCl(2) afforded the corresponding dinuclear complexes , , and , in which metal atoms possess similar trigonal bipyramidal geometries and each ligand functions as a bimetallic bridging binding aminopyridinato moiety with N-donation from the dimethylamino group. While the stoichiometric reaction of with ZrCl(4) gave the mononuclear zirconium complex (6); the seven coordinated zirconium atom adopts a distorted pentagonal bipyramid geometry and the ligand acts as monoanionic η(2)-aminopyridinato moiety with the pendant arm coordinated via N(CH(3))(2). The reaction of with one equivalent of TiCl(4)(THF)(2) produced the interesting dinuclear titanium complex (7) owing to the elimination of a (N,N-dimethylamino)dimethylsilyl group from the original ligand, and the two titanium centers present different coordination geometries. The molecular structures of the crystalline metal complexes have been confirmed by X-ray single crystal diffraction analysis. Upon activation with methylaluminoxane (MAO), both complexes and exhibited moderate catalytic activities toward ethylene polymerization and produced high molecular weight polyethylenes with broad molecular weight distributions.

Synthesis, Structure and Ethylene Polymerization Behavior of Group 4 Metal Complexes Bearing Salicylaldaminato Ligands with Appended Donor Functionality

A series of group 4 metal complexes were synthesized by an equimolar reaction of M(CH2Ph)(4) with (E)-2,4-di-tert-butyl-6-[(phenylimino)methyl]phenol bearing donor functionality. This process involved toluene elimination followed by an intramolecular migration reaction of one benzyl group from metal to the imino carbon, which was supported by the isolation and structural characterization of the intermediate. These new complexes were fully characterized by multinuclear NMR spectroscopy, elemental analyses and X-ray analyses. The titanium complexes showed a very high activity in both ethylene polymerization and ethylene/1-hexene copolymerization upon activation with modified methylaluminoxane (MMAO), whereas the corresponding zirconium and hafnium complexes were almost inactive under the same reaction conditions.

Synthesis, structure, and ethylene polymerization behavior of nickel complexes based on benzoylmethylenetri(2-alkoxylphenyl)phosphorane

Several new nickel complexes are prepared by the treatment of the stabilized ylide benzoylmethylenetri(2-alkoxylphenyl)phosphorane with Ni(cod)(2) in the presence of PPh(3). X-Ray diffraction studies reveal that a distorted square planar geometry around Ni(II) is adopted. Upon treatment with Ni(cod)(2), the nickel complexes are sufficiently robust for ethylene polymerization. The existence of 2-alkoxyl-aryl substituents on phosphorus improves the catalytic activities. The highest activity (2.1 × 10(6) g mol(-1) h(-1)) is achieved when tri(2-isopropoxy-phenyl)phosphorane is employed (5e), which is one order higher than the corresponding SHOP catalyst. NMR analysis shows that the polyethylene mainly contains terminal double bonds and is highly linear.