Activity For Ethylene Polymerization Research Articles

Binuclear Ti(IV) complex with new compartmental ligand 2,6‐(bis‐CF3‐carbinol)‐4‐tert‐butylphenol as precatalysts for ethylene polymerization and its copolymerization with propylene and 5‐ethylidene‐norbornene

AbstractThe coordination chemistry of a new compartmental ligand 2,6‐(bis‐CF3‐carbinol)‐4‐tert‐butylphenol with Ti(IV) and Zr(IV) has been studied. The structures of Al, Ti, and Zr complexes with the participation of this ligand were established by X‐ray diffraction. Upon activation with Et2AlCl or Et3Al2Cl3 and Bu2Mg, Ti(IV) complex exhibited moderate catalytic activity for ethylene polymerization. The obtained UHMWPE samples were processed into high‐strength (up to 2.7 GPa) and high‐modulus (up to 162 GPa) films through solid‐phase molding and orientation drawing. The mononuclear and binuclear Ti(IV) complexes catalyzed the ternary copolymerization of ethylene, propylene, and 5‐ethylidene‐norbornene. Tercopolymers with a content of propylene units up to 36 mol% and 5‐EBN up to 8.6 mol% were synthesized with a high activity (2.8–6.3 tons of copolymer/mol Ti h); the mechanical characteristics of elastomeric materials have been studied.

The Stronger the Better: Donor Substituents Push Catalytic Activity of Molecular Chromium Olefin Polymerization Catalysts.

The donor strength of bifunctional pyridine‐cyclopentadienyl ligands was altered systematically by the introduction of donating groups in the para‐position of the pyridine. In the resulting chromium complexes an almost linear correlation between donor strength and the nitrogen‐chromium distance as well as the electronic absorption maximum is experimentally observed. The connection of electron‐donating groups in the ligand backbone leads to an efficient transfer of the electronic influences to the catalytically active metal centre without restricting it through steric effects. Therefore, catalytic olefin polymerization activity, which is already very high for the previously studied catalysts, increase considerably by attaching para‐amino groups to the chelating pyridine or quinoline, respectively. Combining electron‐rich indenyl ligands with para‐amino substituted pyridines lead to the highest catalytic activities observed so far for this class of organo chromium olefin polymerisation catalysts. The resulting polymers are of ultra‐high molecular weight and the ability of the catalysts to incorporate co‐monomers is also very high.

Exploring ortho‐(4,4′‐dimethoxybenzhydryl) substitution in iron ethylene polymerization catalysts: Co‐catalyst effects, thermal stability, and polymer molecular weight variations

Six different types of 4,4′‐dimethoxybenzhydryl‐substituted bis(arylimino)pyridine‐iron(II) chloride complex—[2‐{{2,6‐((p‐MeOPh)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‐MeOPh)2CH)2‐4‐MeC6H2 (Fe6)—are reported. The molecular structures of Fe2 and Fe3 emphasize the unsymmetrical nature of the N,N,N‐chelating ligand and the steric protection exerted by the ortho‐(4,4′‐dimethyoxybenzhydryl) groups. A range in catalytic activities for ethylene polymerization was observed when Fe1–Fe6 were treated with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO). In particular, Fe1/MAO bearing the least bulky N‐2,6‐dimethylphenyl group exhibited a very high activity of 1.11 × 107 g (PE) mol−1 (Fe) h−1 at 70°C/10 atm over a 30‐min run time that remained high even after 60 min, an observation highlighting its appreciable catalyst lifetime and thermal stability. In addition, the polyethylene formed by this catalyst class displayed desirable characteristics such as high linearity and high molecular weight (Mw range: 5.17–7.62 × 105 g mol−1). Indeed, the molecular weight of the polymer produced using Fe1 (with MAO or MMAO) exceeds that obtained using related benzhydryl‐containing bis(imino)pyridine‐iron catalysts. As a general feature, activation of Fe1–Fe6 with MMAO led to lower activity and lower molecular weight polyethylene, especially for runs performed at 1 atm ethylene pressure.

Ethylene Polymerization Activity of (R3P)Ni(codH)+ (cod = 1,5-cylcooctadiene) Sites Supported on Sulfated Zirconium Oxide.

PAr3 containing o-OMe, o-Me, or o-Et substituents reacts with Brønsted sites on sulfated zirconium oxide (SZO) to form [HPAr3][SZO]. The phosphonium sites on this material react with bis(cyclooctadiene)nickel [Ni(cod)2] to form [Ni(PAr3)(codH)][SZO] that are active in ethylene polymerization reactions. Selective poisoning studies with pyridine show that ∼90% of the Ni(PAr3)(codH)+ sites in this material are active in polymerization reactions.

Metallocene encapsulated within a hybrid silica-polystyrene support

A series of heterogeneous metallocene catalysts were prepared by encapsulating Cp2ZrCl2 within silica-polystyrene hybrid support. Immobilization was performed through a non-hydrolytic sol–gel process in which polystyrene (PS) dissolved in toluene and metallocene (1% by wt) were combined. The effect of PS (0 to 5% by wt) and silicon tetrachloride (0.5 to 1.6 [TEOS]/[SiCl4]) was evaluated in terms of catalyst activity in ethylene polymerization with methylaluminoxane as the cocatalyst. According to FTIR measurements, an increase in PS content promoted a decrease in (SiO)6 content, which indicated the formation of more compact structures. Furthermore, homogeneous distributions of polymer and silica phases were observed both in bulk and on the support surface. The results showed very small surface areas (< 20 m2 g−1), probably because PS would fill the silica pores. The catalytic activity for ethylene polymerization was shown to decrease with increasing polystyrene content within the catalyst support of low surface area. A positive correlation was found between the (SiO)6 content and catalyst activity. The increase in the PS content was followed by an increase in the degree of polyethylene crystallization, which ranged from 77 to 84%.

Rational Design of Cycloheptyl‐Fused Bis(arylimino)pyridyl‐cobalt(II) Precatalysts Adorned with Sterically and Electronically Modified N‐Aryls for Enhancing Ethylene Polymerization

AbstractThe sterically and electronically modified cycloheptyl‐fused bis(arylimino)pyridine‐cobalt(II) chloride precatalysts [2,3 : 5,6‐{C4H8C(N‐2,4‐(C15H13)‐6‐R‐C6H2}2C5HN]CoCl2 (R=Me (Co1), Et (Co2), i‐Pr (Co3), Cl (Co4), and F (Co5)) have been prepared via one‐pot synthesis approach. All the precatalysts were characterized by elemental analysis, FT‐IR spectroscopy and the single‐crystal X‐ray diffraction for Co2 confirmed distorted‐square‐pyramidal geometry around the cobalt center. On activation with either MAO (methylaluminoxane) or MMAO (modified methylaluminoxane), all the cobalt precatalysts displayed high catalytic activities for ethylene polymerization with peak performance of 3.47×106 g (PE) mol−1 (Co) h−1 at 50 °C using MAO and 4.53×106 g (PE) mol−1 (Co) h−1 at 30 °C with MMAO. The steric and electronic influence of the ortho‐substitutions (R) displayed significant effect on the catalytic activity and molecular weight of the resultant polyethylene. Notably, the precatalyst Co5 (R=F) exhibited high activity, delivering high‐molecular‐weight (558.17 kg mol−1) polyethylene; highlights the beneficial effect of ortho‐substituents (R) alongside with dibenzocycloheptyl groups. In addition, analysis of the obtained polyethylene showed strictly linear structure with saturated and unsaturated (vinyl) end groups.

2,4,6‐Triphenylpyridinium: A Bulky, Highly Electron‐Withdrawing Substituent That Enhances Properties of Nickel(II) Ethylene Polymerization Catalysts

AbstractThe reactivity of NiII and PdII olefin polymerization catalysts can be enhanced by introduction of electron‐withdrawing substituents on the supporting ligands rendering the metal centers more electrophilic. Reported here is a comparison of ethylene polymerization activity of a classical salicyliminato nickel catalyst substituted with the powerful electron‐withdrawing 2,4,6‐triphenylpyridinium (trippy) group to the ‐CF3 analogue. The trippy substituent is substantially more electron‐withdrawing (σmeta=0.63) than the trifluoromethyl group (σmeta=0.43) which results in a ca. 8‐fold increase in catalytic turnover frequency. An additional advantage of trippy is the high steric bulk relative to the trifluoromethyl group. This feature results in a four‐fold increase in polymer molecular weight owing to enhanced retardation of chain transfer. A significant increase in catalyst lifetime is observed as well.

Highly Flowable Nano TiO2/Porous Organic Polymer (POP) Supports for Efficient Metallocene Catalysts.

Porous organic polymers (POPs) have proven to be an efficient support in the olefin polymerization catalyst field. In this paper, nano TiO2 beads were used to modulate the pore structure, bulk density, and surface morphology and flowability of the prepared POPs. With the incorporation of the hydrophilic nano TiO2 beads, the prepared TiO2/POP supports obtained reasonable specific surface area (100–300 m2/g) and higher bulk density (0.26–0.35 g/mL) and flowability than the pure POP supports. The results show that bulk density of the prepared TiO2/POP particles increased when adding an increased amount of TiO2, and when 37.5% TiO2 (weight percent to the total comonomers divinylbenzene (DVB) and 2-hydroxyethyl methacrylate (HEMA)) and 3:1 DVB/HEMA (molar ratio) were added, highly flowable TiO2/POP composites (POP-6 and POP-7) were obtained. With the modulation of the nano TiO2 template during the support synthesis, the prepared POP-7 particles successfully achieved a normal distribution with a narrow particle size distribution (PSD) of 0.717 and average particle size of 24.1 μm, a specific surface area (SSA) of 279 m2/g, and relatively high bulk density of 0.30 g/mL. Furthermore, all the prepared TiO2/POP supports obtained higher ethylene polymerization activity than silica gel-supported commercial metallocene catalyst. The immobilized (n-BuCp)2ZrCl2/MAO@POP-7 catalyst exhibited the highest ethylene polymerization activity of 4794 kg PE/mol Zr.bar.h and productivity of 389 g PE/g cat, more than twice that of the commercial counterpart. Even higher catalyst productivity (3197 g PE/g cat) and bulk density of the produced PE (0.36 g/mL) could be obtained in higher ethylene partial pressure at 80 °C for 2 h, and the prepared TiO2/POP catalyst shows no obvious Zr+ active sites decay during the ethylene polymerization.

Cationic α-Diimine Nickel and Palladium Complexes Incorporating Phenanthrene Substituents: Highly Active Ethylene Polymerization Catalysts and Mechanistic Studies of syn/anti Isomerization

α-Diimine palladium complexes incorporating phenanthryl- and 6,7-dimethylphenanthrylimino groups have been synthesized and characterized. The (diimine)PdMeCl complexes prepared from 2,3-butanedione...

Reversion of the chain walking ability of α-diimine nickel and palladium catalysts with bulky diarylmethyl substituents

In general, α-diimine palladium species are more likely to undergo chain walking than the corresponding nickel species, resulting in more branched and topological polyethylene. Moreover, the ligand steric effects have a significant influence on the chain walking in α-diimine system. In this contribution, a series of acenaphthene-based α-diimine ligands bearing bulky diarylmethyl moieties with various electronic effects and the corresponding Ni(II) and Pd(II) complexes were synthesized and characterized. These Ni(II) complexes exhibit high activities in ethylene polymerization even at 80 °C, generating ultrahigh-molecular-weight polyethylenes with low branching density and high melting temperature. The corresponding palladium complexes display moderate activity, leading to semicrystalline polyethylene with low branching density and high melting temperature. Polar functionalized semicrystalline polyethylene with high melting temperature can also be obtained via copolymerization of ethylene with polar monomers using these palladium complexes. Moreover, the remote nonconjugated electronic substituents exert a great influence on the ethylene (co)polymerization. Most importantly, the chain walking ability of metal species can be controlled by changing the ligand steric environment, and the diarylmethyl substituents can even reverse the chain walking trend of palladium and nickel species.

Versatile PNPO ligands for palladium and nickel catalyzed ethylene polymerization and copolymerization with polar monomers

Asymmetric PO-type ligands are versatile platforms for palladium and nickel catalyzed ethylene polymerization as well as copolymerization of ethylene with polar monomers. In this work, a series of phosphinoamine phosphoramidate/phosphoramide ligands and the corresponding palladium/nickel catalysts were prepared, characterized and investigated in ethylene polymerization as well as copolymerization of ethylene with various polar monomers. The palladium and nickel complexes exhibited high activities in ethylene (co) polymerization, generating high-molecular-weight polyethylenes and copolymers of ethylene and polar monomers. The introduction of electron-donating substituents in the palladium catalytic system can significantly increase polymer molecular weights while maintaining high ethylene (co)polymerization activities. The less electronic donating substituents in the nickel catalysts led to increased catalytic activities in both ethylene polymerization and copolymerization with polar monomers. These results demonstrate the importance of ligand electronic effect in tuning the properties of nickel and palladium catalysts in ethylene polymerization and copolymerization reactions.

Octadecyl‐modified silica supports for metallocene catalyst applied in ethylene polymerization

AbstractChemical modification of silica‐based supports is an alternative route for modulating the active sites of metallocene catalysts, presenting the potential to obtain polyethylenes with improved properties. Therefore, this work investigates the effect of octadecylsilane content in silica support on the behavior of resulting supported metallocene catalysts on ethylene polymerization. For this propose, a series of octadecyl‐modified silicas whit different amounts of octadecyl (ODS) groups were synthesized by a modified Stöber sol–gel method and then applied as supports for a metallocene catalyst. The supported metallocene catalysts were evaluated in ethylene polymerization and ethylene/1‐hexene copolymerization reactions. Besides, studies of the growth kinetics of polyethylene particles in a gas phase reactor were performed using videomicroscopy. The octadecylsilane content in the supports was in the range of 0.2 to 1.4 mmol g−1. DRIFTS and 13C CP/MAS NMR results showed a predominance of an all‐trans octadecyl chain conformation. SEM images showed spherical particle morphology for silicas having octadecylsilane content up to 0.6 mmol g−1. The supported catalysts presented activity in ethylene polymerization in the range of 1100–1900 kg PE molZr−1 h−1 bar−1. The surface polarity of the catalyst influenced the molar mass of the resulting polyethylene. The increase of the ODS content on the silica surface led to a supported catalyst with slower kinetic behavior in the gas phase, which might be attributed to the diffusive effects of the octadecyl layer on the catalyst surface.

Crystal Structure of Decakis(μ-chloro)-tetrakis(1,2,4-triphenylcyclopentadienyl)-hexakis(tetrahydrofuran)-di-potassium-tetra-neodymium(III) Tetrahydrofuran Trisolvate

The crystal structure of decakis(μ-chloro)-tetrakis(1,2,4-triphenylcyclopentadienyl)-hexakis(tetrahydrofuran)-di-potassium-tetra-neodymium(III) tetrahydrofuran trisolvate, 1, is reported. The centrosymmetric complex 1 has a rare tetranuclear core [Ln4K2Cl10] and crystalizes in triclinic space group (P $$\bar{1}$$ ) with unit cell parameters: a = 11.9858(3) A, b = 14.0698(3) A, c = 19.8129(4) A, α = 74.1120(4)°, β = 81.2073(4)°, γ = 83.9521(4)° and Z = 1. The catalytic system based on 1 and nBuMg(O-2,6-tBu2-4-MeC6H2) exhibits moderate activity in coordinative chain transfer polymerization of ethylene. In case of the system 1/nBu2Mg, oligomerisation of ethylene was not detected. The mono(cyclopentadienyl) complex {[1,2-Ph2-4-(2-MeOC6H4)C5H2]NdCl5K(THF)2}2(THF)3 has been obtained from NdCl3(THF)2.5 and K[1,2-Ph2-4-(2-MeOC6H4)C5H2] (1:1) in THF, crystallized from a THF/hexane mixture, and structurally characterized.

Adjusting Ortho-Cycloalkyl Ring Size in a Cycloheptyl-Fused N,N,N-Iron Catalyst as Means to Control Catalytic Activity and Polyethylene Properties

Five examples of bis(arylimino)tetrahydrocyclohepta[b]pyridine dichloroiron(II) complex, [2-{(Ar)N=CMe}-9-{N(Ar)}C10H10N]FeCl2 (Ar = 2-(C5H9)-4,6-(CHPh2)2C6H2Fe1, 2-(C6H11)-4,6-(CHPh2)2C6H2Fe2, 2-(C8H15)-4,6-(CHPh2)2C6H2Fe3, 2-(C12H23)-4,6-(CHPh2)2C6H2Fe4, and 2,6-(C5H9)2-4-(CHPh2)C6H2Fe5), incorporating ortho-pairings based on either benzhydryl/cycloalkyl (ring sizes ranging from 5 to 12) or cyclopentyl/cyclopentyl groups, have been prepared in reasonable yield by employing a simple one-pot template strategy. Each complex was characterized by FT-IR spectroscopy, elemental analysis, and for Fe3 and Fe5 by single crystal X-ray diffraction; pseudo-square pyramidal geometries are a feature of their coordination spheres. On treatment of Fe1–Fe5 with modified methylaluminoxane (MMAO) or methylaluminoxane (MAO), a range in catalytic activities for ethylene polymerization were observed with benzhydryl/cyclopentyl-containing Fe1/MMAO achieving the maximum level of 15.3 × 106 g PE mol−1 (Fe) h−1 at an operating temperature of 70 °C. As a key trend, the activity was found to drop as the ortho-cycloalkyl ring size increased: Fe1C5H9/CHPh2~Fe5C5H9/C5H9 &gt; Fe2C6H11/CHPh2 &gt; Fe3C8H15/CHPh2 &gt; Fe4C12H23/CHPh2. Furthermore, strictly linear polyethylenes (Tm &gt; 126 °C) were formed with molecular weights again dependent on the ortho-cycloalkyl ring size (up to 55.6 kg mol−1 for Fe1/MAO); narrow dispersities were a characteristic of all the polymers (Mw/Mn range: 2.3–4.7), highlighting the well-controlled nature of these polymerizations.

The electronic effects on unsymmetrical Bis(imino)pyridyl iron(ii) catalyzed ethylene polymerization

A series of bulky unsymmetrical bis(imino)pyridyl iron(II) complexes 1–3 with different electronic effect substituents at the para-position of the N-aryl group have been synthesized and characterized. These highly robust thermostable iron(II) complexes display very high activity (up to 2.5 × 107 g mol−1 h−1) in ethylene polymerization at high pressure, and can generate highly linear polyethylene (Tm = 131.6–138.8 °C) with high molecular weight (Mw up to 185.7 × 104 g mol−1) and broad molecular weight distributions (PDI: 2.34–13.68). The electronic effect and influence of polymerization conditions on activity and molecular weight of polyethylene are investigated in detail. The electronic perturbations show great influence on the activity and polyethylene molecular weight in ethylene polymerization. Compared with the classical isopropyl substituted iron(II) complex 4, the bulky iron(II) complexes 1–3 showed higher activity and thermal stability in ethylene polymerization at high temperature.

Synthesis, structure and ethylene polymerisation activity of {η5:η1(N)-1-[(tert-butylamido)diphenylsilyl)]-2,3,4,5-tetramethylcyclopentadienyl}dichlorotitanium(IV)

The permethylcyclopentadienyl diphenylsilylene-bridged titanium constrained geometry complex [TiCl2{η5-C5Me4(SiPh2NCMe3-κN)}] (2) was synthesised following the common synthetic route and subsequently characterised by spectral analyses and by single-crystal X-ray diffraction. The comparison of its solid-state structure with that of the parent dimethylsilylene CGC complex [TiCl2{η5-C5Me4(SiMe2NCMe3-κN)}] (1) revealed only negligible geometry differences between their cyclopentadienyl centroid-Ti-N-Si skeletons. A significantly different positioning was however observed for the amine tBu substituent of the DFT-optimised methyl-substituted cationic catalytical species (1a, 2a), which are supposed to be generated from 1 and 2 in the presence of methylaluminoxane (MMAO). A lower ethylene polymerisation activity of 2-MMAO system compared to that of 1-MMAO is compatible with the higher steric congestion at the metallic centre due to the tBu ligand becoming rotated more into the open space in 2b. This arrangement aggravates monomer access throughout the catalytical process and decreases the coordination unsaturation of the central atom through the formation of auxiliary agostic interaction.

Structure-performance relationship of Mg(OEt)2-based Ziegler-Natta catalysts

A multivariate aspect has hampered the clarification of structure-performance relationships in heterogeneous Ziegler-Natta olefin polymerization catalysis. Here, 16 catalyst samples were prepared using Mg(OEt)2 support precursors with different particle architectures. They were fingerprinted based on a series of characterization and analytical methods. In a pairwise correlation analysis, none of structural features (such as particle size and pore volume) exhibited a clear correlation with ethylene polymerization performance. However, compound features created among different structural features reasonably reproduced the ethylene polymerization activity as well as 1-hexene incorporation efficiency, where a negative influence of pores with the size below 10 nm was dictated.

O‐Trityl phenoxy‐imino vanadium (III) complexes: synthesis, characterization, and catalysis on ethylene (co)polymerization

Several phenoxy‐imine ligands bearing o‐trityl group in phenoxy moiety RN=CHArOH (Ar = C6H2(CPh3)tBu, R = 2,6‐Me2C6H3 (L1H); 2,6‐iPr2C6H3 (L2H); 3,5‐(CF3)2C6H3 (L3H); 3,5‐(OMe)2C6H3 (L4H); CHPh2 (L5H); CPh3 (L6H)) were synthesized and characterized by1H NMR and 13C NMR spectroscopy. The vanadium complexes based on these ligands LVCl2(THF)2 (1–6) were synthesized via conventional transmetalation reaction in moderate to high yields. Complexes 1–6 were fully characterized by FT‐IR, elemental analyses and the molecular structures of 1, 2·H2O, (2·H2O)2(μ‐Cl)2, 4, and 5 were confirmed by X‐ray crystallographic analysis in which the six‐coordinated vanadium centers are in a typical octahedral geometry. Upon activation with Et2AlCl in toluene, complexes 1–6 showed high activities in ethylene polymerization affording polymers with moderate molecular weight (5.9–11.8 × 104 Da). Moreover, in hexane or CH2Cl2, 1–6/Et2AlCl exhibited enhanced activities. When activated with MAO or MMAO in toluene, these complexes showed relatively low activities but afforded polymers with ultra‐high molecular weight (up to 3.30 × 106 Da). 1–6/Et2AlCl also showed high activities in ethylene/1‐hexene copolymerization at room temperature giving moderate molecular‐weight polymers (6.5–11.4 × 104 Da) with co‐monomer incorporation being of 6.0 ~ 7.8%.

Binuclear titanium complexes coordinated by rigid p‐phenylene linked bis‐β‐carbonylenamine: Synthesis, structure, ethylene polymerization and copolymerization with 1,5‐hexadiene

Binuclear complexes for olefin polymerization have attracted great attention due to their unique catalytic properties compared with their mononuclear counterparts. Here a series of p‐phenylene‐bridgedbis‐β‐carbonylenamine ligands and their binuclear Ti complexes Ti2L1–Ti2L3 were prepared and characterized by 1H NMR, 13C NMR, Fourier transform infrared spectroscopy, and elemental analysis. The binuclear complex Ti2L3 bearing an octylthio sidearm was further investigated by single‐crystalX‐ray diffraction, which revealed that the ligand was of β‐imino enol form, with one titanium atom ligated with six other atoms, forming a deformed octahedral configuration. Furthermore, the ligand in Ti2L3 adopted a cis configuration, which was different from the trans configuration of its m‐phenylene‐bridged derivatives. These binuclear complexes (Ti2L1–Ti2L3) could catalyze ethylene polymerization and copolymerization with 1,5‐hexadiene(1,5‐HD) efficiently under modified methylaluminoxane activation. Compared with the mononuclear complex TiL5, the binuclear catalysts were thermally more stable and showed higher activity for ethylene polymerization at higher temperatures. The activity of these titanium complexes for the copolymerization of ethylene with 1,5‐HD were over 106 g/mol Ti.h.atm, almost twice as high as for homopolymerization. Compared with the mononuclear analogue TiL5 and the m‐substituted binuclear derivative Ti2L4, binuclear catalyst Ti2L2 showed higher activity and insertion rate of the comonomer. The activity of Ti2L2 was two to three times higher than that of TiL5 and Ti2L4, indicating that p‐substituted binuclear catalysts generate clear bimetallic synergistic effect for the copolymerization of ethylene and 1,5‐HD. Meanwhile, 1,5‐HD takes 1,3‐cyclopentyl form in the polymer by 1,3‐insertion. The copolymer prepared by binuclear catalysts had higher molecular weight and wider molecular weight distribution than that prepared by the mononuclear catalyst.

Study of supported catalysts, prepared via binding of Fe(II) bis(imino)pyridyl complex with silica, modified by alumina: Effect of surface Lewis acidic sites on catalyst composition and activity in ethylene polymerization

In this work we present the data on the formation and composition of new supported catalysts for ethylene polymerization, prepared by interaction of Fe(II) bis(imino)pyridyl complex (LFeCl2) with silica, modified by introduction of alumina compounds (SiO2(nAl)) for generation of Lewis acidic sites (LAS) on the silica surface. Data on the content of LAS with different acidity in SiO2(nAl) supports and on the interaction of LFeCl2 with these sites were obtained. It was found that interaction of LFeCl2 with the most acidic sites of SiO2(nAl) supports leads to formation of the most active catalysts for the ethylene polymerization.