Preparation of functionalized montmorillonites and their application in supported zirconocene catalysts for ethylene polymerization

Ethylene polymerization was carried out with zirconocene catalysts supported on montmorillonite (or functionalized montmorillonite). The functionalized montmorillonite was from simple ion exchange of [CH₃O₂CCH₂NH₃]⁺ (MeGlyH⁺) ions with interlamellar cations of layered montmorillonites. The functionalized montmorillonites [high‐purity montmorillonite (MMT)‐MeGlyH⁺] had larger interlayer spacing (12.69 Å) than montmorillonites without treatment (9.65 Å). The zirconocene catalyst system [Cp₂ZrCl₂/methylaluminoxane (MAO)/MMT‐MeGlyH⁺] had much higher Zr loading and higher activities than those of other zirconocene catalyst systems (Cp₂ZrCl₂/MMT, Cp₂ZrCl₂/MMT‐MeGlyH⁺, Cp₂ZrCl₂/MAO/MMT, [Cp₂ZrCl]⁺[BF₄]/MMT, [Cp₂ZrCl]⁺[BF₄]^?/MMT‐MeGlyH⁺, [Cp₂ZrCl]⁺[BF₄]^?/MAO/MMT‐MeGlyH⁺, and [Cp₂ZrCl]⁺[BF₄]^?/MAO/MMT). The polyethylenes with good bulk density were obtained from the catalyst systems, particularly (Cp₂ZrCl₂/MAO/MMT‐MeGlyH⁺). MeGlyH⁺ and MAO seemed to play important roles for preparation of the supported zirconocenes and polymerization of ethylene. The difference in Zr loading and catalytic activity among the supported zirconocene catalysts is discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1892–1898, 2002     

Donor- and acceptor-modified metallocene-based homogeneous Ziegler-Natta catalysts

The polymerization kinetics of propene polymerization using metallocene/methylaluminoxane (MAO) homogeneous catalysts have been investigated to explore the role of donor/acceptor interactions and to enhance the catalyst productivities. In the case of the non-stereospecific Cp₂ZrCl₂/MAO model system it has been demonstrated that, in addition to the well known irreversible deactivation, reversible deactivations, which are second order relative to the zirconium active site concentration, account for the decay of the polymerization rate. While MAO injection during polymerization enhances the polymerization rate, zirconocene addition deactivates the catalyst which can be reactivated by injecting additional MAO. A sequence of dynamic equilibria involving the formation of active cationic metallocene intermediates as well as inactive zirconocene species, e.g., zirconocene dimers, is proposed. Lewis base and Lewis acid additives have been added as probes to examine the role of such equilibria in the case of metallocene-based catalyst systems such as MAO-activated Cp₂ZrCl₂, racemic ethylenebisindenyl zirconium dichloride (EBIZrCl₂), and racemic ethylenebis (4,5,6,7-tetrahydroindenyl) zirconium dichloride (EBTHIZrCl₂). While the conventional donors such as 2,6-ditert.butyl-4-methylphenol (BHT) and 2,2,6,6-tetramethylpiperidine (TMP) reduce catalyst productivities, even at very low donor/Al molar ratios, increasing propene concentration and addition of trimethylboroxine (TMB) substantially enhance catalyst productivities and affect molecular weights of the polypropylene produced with metallocene/MAO catalysts.     

Heterogeneous zirconocene catalyst on magnesium support MgCl2(THF)2 modified by AlEt2Cl for ethylene polymerisation

The heterogeneous bis(cyclopentadienyl)zirconium(IV) dichloride catalyst of the composition MgCl₂(THF)/(AlEt₂Cl)_0.34/(Cp₂ZrCl₂)_0.01 as determined by FTIR, XRD, and AAS analyses was synthesised and, after activation by MAO, applied for ethylene polymerisation. The catalyst turned out to be stable and more active than those magnesium supported catalysts already known from the literature. The polyethylene produced has a relatively high molecular weight (M_w > 200,000 g/mol), a narrow and monomodal molecular weight distribution (MWD = 2.4), a bulk density of about 180 g/dm³, and monomodal particle size distribution. Application of a ternary Al(i-Bu)₃/MAO/B(C₆F₅)₃ activator decreased the amount of MAO needed and increased catalyst activity, but did not change the reaction mechanism.     

Synthesis and properties of poly‐1‐olefins

The oligomerization and polymerization of 1‐pentene using Cp₂ZrCl₂, Cp₂HfCl₂, [(CH₃)₅C₅]₂ZrCl₂, rac‐[C₂H₄(Ind)₂]ZrCl₂, [(CH₃)₂Si(Ind)₂]ZrCl₂, (CH₃)₂Si(2‐methylbenz[e]indenyl)₂ZrCl₂, Cp₂ZrCl{O(Me)CW(CO)₅}, Cp₂ZrCl(OMe) and methylaluminoxane (MAO) has been studied. The degree of polymerization was highly dependent on the metallocene catalyst. Oligomers ranging from the dimer of 1‐pentene to polymers of poly‐1‐pentene with a molar mass M_w = 149000 g/mol were formed. Cp₂ZrCl{O(Me)CW(CO)₅} is a new highly active catalyst for the oligomerization of 1‐pentene to low molecular weight products. The activity decreases in the order Cp₂ZrCl{O(Me)CW(CO)₅} > Cp₂ZrCl₂ > Cp₂ZrCl(OMe). Furthermore, poly‐1‐olefins ranging from poly‐1‐pentene to poly‐1‐octadecene were synthesized with (CH₃)₂Si(2‐methyl‐benz[e]indenyl)₂ZrCl₂ and methylaluminoxane (MAO) at different temperatures. The temperature dependence of the molar mass can be described by a common exponential decay function irrespective of the investigated monomer.     

Propene polymerization using homogeneous MAO-activated metallocene catalysts: Me2Si(Benz[e]Indenyl)2ZrCl2/MAO vs. Me2Si(2-Me-Benz[e]Indenyl)2ZrCl2/MAO

Propene was polymerized at 40°C and 2-bar propene in toluene using methylalumoxane (MAO) activated rac-Me₂Si(Benz[e]Indenyl)₂ZrCl₂ ( BI ) and rac-Me₂Si(2-Me-Benz[e]Indenyl)₂ZrCl₂ ( MBI ). Catalyst BI /MAO polymerizes propene with high activity to afford low molecular weight polypropylene, whereas MBI /MAO is less active and produces high molecular weight polypropylene. Variation of reaction conditions such as propene concentration, temperature, concentration of catalyst components, and addition of hydrogen reveals that the lower molecular weight polypropylene produced with BI /MAO results from chain transfer to propene monomer following a 2,1-insertion. A large fraction of both metallocene catalyst systems is deactivated upon 2,1-insertion. Such dormant sites can be reactivated by H₂-addition, which affords active metallocene hydrides. This effect of H₂-addition is reflected by a decreasing content of head-to-head enchainment and the formation of polypropylene with n-butyl end groups. Both catalysts show a strong dependence of activity on propene concentration that indicates a formal reaction order of 1.7 with respect to propene. MBI /MAO shows a much higher dependence of the activity on temperature than BI /MAO. At elevated temperatures, MBI /MAO polymerizes propene faster than BI /MAO. © 1995 John Wiley & Sons, Inc.     

Metallocene/mao polymerization catalysts supported on cyclodextrin

By treating cyclodextrin(CD) with methylaluminoxane (MAO such as PMAO or MMAO) or trimethylaluminium (TMA) followed by Cp₂ZrCl₂, CD/PMAO/Cp₂ZrCl₂, CD/MMAO/Cp₂ZrCl₂ and CD/TMA/Cp₂ZrCl₂ catalysts were prepared. The catalysts were analyzed by ¹³C-CP/MAS NMR spectrometer and ICP to examine the structure of catalyst and content of Zr and Al. Ethylene polymerization was conducted with MAO or TMA as cocatalyst. Styrene polymerization was also carried out with α-CD/MMAO/Cp*TiCl₃ and α-CD/TMA/Cp*TiCl₃ catalysts. While the ordinary trialkylaluminium such as TMA as well as MAO can be used as cocatalyst for ethylene polymerization, only MAO could initiate the styrene polymerization with α-CD supported catalysts.     

Surface chemistry of selected supported metallocene catalysts studied by DR‐FTIR,CPMAS NMR,and XPS techniques

Two supported metallocene catalysts (CS 1: PQ 3030/MAO/Cp₂ZrCl₂ and CS 2: PQ 3030‐BuGeCl₃/MAO/Cp₂ ZrCl₂) were prepared by sequentially loading MAO and Cp₂ZrCl₂ on partially dehydroxylated silica PQ 3030. In catalyst CS 2, ⁿBuGeCl₃ was used to functionalize the silica. These catalysts were characterized by DR‐FTIR spectroscopy, CPMAS NMR spectroscopy, and XPS. Their catalytic performance was evaluated by polymerizing ethylene using the MAO cocatalyst and characterizing the resulting polymers by GPC. Both catalysts produced two metallocenium cations (Cation 1: [Cp₂ZrCl]⁺ and Cation 2: [Cp₂ZrMe]⁺) with comparable equilibrium concentrations and showed varying solid‐state electronic environments. The modified supports (PQ 3030/MAO and PQ 3030‐BuGeCl₃/MAO) acted as weakly coordinating polyanions and stabilized the above cations. BuGeCl₃ did not affect the solid‐state electronic environment. However, it increased the surface cocatalyst to catalyst molar ratio (Al:Zr), acted as a spacer, increased catalyst activity, and enhanced chain‐transfer reactions. The separately fed MAO cocatalyst shifted the equilibrium between Cation 1 and Cation 2 toward the right. Consequently, more Cation 2 was generated, which acted as the effective and active single‐site catalytic species producing monomodal PDI. Copyright © 2006 John Wiley & Sons, Ltd.     

过渡金属氢化物和聚集双键化合物反应的研究——Ⅴ.Cp2MH2(M=Zr,Hf)与RNCS(R=n-Bu,c-C6H11,C6H5,2-C10H7)、CS2的反应

本文研究了Cp₂ZrH₂与CS₂、RNCS(R=n-Bu,c-C₆H₁1,C₆H₅,2-C₁₀H₇)和Cp₂HfH₂与c-C₆H₁₁NCS的反应,探讨了在这类新型脱硫反应中锆氢与铪氢配合物化学反应性能上的差异.从以上反应中分     

Copolymerization of ethylene with 1‐hexene over metallocene catalyst supported on complex of magnesium chloride with tetrahydrofuran

The study of ethylene/1‐hexene copolymerization with the zirconocene catalyst, bis(cyclopentadienyl)zirconium dichloride (Cp₂ZrCl₂)/methylaluminoxane (MAO), anchored on a MgCl₂(THF)₂ support was carried out. The influence of 1‐hexene concentration in the feed on catalyst productivity and comonomer reactivity as well as other properties was investigated. Additionally, the effect of support modification by the organoaluminum compounds [(MAO, trimethlaluminum (AlMe₃), or diethylaluminum chloride (Et₂AlCl)] on the behavior of the MgCl₂(THF)₂/Cp₂ZrCl₂/MAO catalyst in the copolymerization process and on the properties of the copolymers was explored. Immobilization of the Cp₂ZrCl₂ compound on the complex magnesium support MgCl₂(THF)₂ resulted in an effective system for the copolymerization of ethylene with 1‐hexene. The modification of the support as well as the kind of organoaluminum compound used as a modifier influenced the activity of the examined catalyst system. Additionally, the profitable influence of immobilization of the homogeneous catalyst as well as modification of the support applied on the molecular weight and molecular weight distribution of the copolymers was established. Finally, with the successive self‐nucleation/annealing procedure, the copolymers obtained over both homogeneous and heterogeneous metallocene catalysts were heterogeneous with respect to their chemical composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2512–2519, 2004     

Recent Chemistry Based on the [RuCp(CH3CN)3]+ Cation: Reappraisalof an Old Precursor

 This article gives an overview of recent chemistry based on the tris-acetonitrile complex [RuCp(CH₃CN)₃]⁺. Due to the labile nature of the CH₃CN ligands, substitution reactions are a dominant feature of this complex. Important derivatives are the highly reactive complexes [RuCp(PR ₃)(CH₃CN)₂]⁺ which are a source of the 14e⁻ fragment [RuCp(PR ₃)]⁺. These species are catalytically active in the redox isomerization of allyl alcohols to give aldehydes and ketones. Furthermore, the cationic complex [RuCp(κ¹(P),η²-PPh₂CH₂CH₂CH*CH₂)(CH₃CN)]PF₆ derived from the reaction of [RuCp(CH₃CN)₃]⁺ with PPh₂CH₂CH₂CH*CH₂ is a model compound for studying coupling reactions of olefins and acetylenes. In addition, [RuCp(CH₃CN)₃]⁺ is a valuable precursor for the synthesis of configurationally stable chiral three-legged piano-stool ruthenium complexes. These are currently being intensively investigated as Lewis acid catalysts in asymmetric synthesis.     

Effect of methylaluminoxane/transition-metal ratio on the physical properties and chemical composition distributions of ethylene-hexene copolymers produced by a rac-Et(Ind)2ZrCl2/TiCl4/MAO/SMB catalyst

A silica-magnesium bisupport (SMB) was prepared by a sol-gel method for use as a support for the impregnation of TiCl₄ and rac-Et(Ind)₂ZrCl₂. The prepared rac-Et(Ind)₂ZrCl₂/TiCl₄/MAO(methylaluminoxane)/SMB catalyst was applied to the ethylene-hexene copolymerization under the conditions of variable Al(MAO)/Zr ratio and fixed Al(TEA, triethylaluminum)/Ti ratio. The effect of Al(MAO)/Zr ratio on the physical properties and chemical composition distributions of ethylene-hexene copolymers produced by a rac-Et(Ind)₂ZrCl₂/TiCl₄/MAO/SMB catalyst was investigated. The catalytic activity of rac-Et(Ind)₂ZrCl₂/TiCl₄/MAO/SMB was steadily increased with increasing Al(MAO)/Zr ratio from 200 to 500. The ethylene-hexene copolymer produced with Al(MAO)/Zr = 300, 400, and 500 showed two melting points at around 110 °C and 130 °C, while that produced with Al(MAO)/Zr = 200 showed one melting point at 136 °C. The number of chemical composition distribution (CCD) peaks was increased from 4 to 7 and the short chain branches of ethylene-hexene copolymer were distributed over lower temperature region with increasing Al(MAO)/Zr ratio. The lamellas in the copolymer were distributed over lower temperature region and the small lamellas in the copolymer were increased with increasing Al(MAO)/Zr ratio. The rac-Et(Ind)₂ZrCl₂/TiCl₄/MAO/SMB catalyst preferably produced a ethylene-hexene copolymer with non-blocky sequence ([EHE]) with increasing Al(MAO)/Zr ratio.     

Reduction reactions of the metallocene complex (η-C5H4CMe2C9H7)2ZrCl2

The preparation and characterization of the substituted bis(cyclopentadienyl) zirconium dichloride complexes (η⁵-C₅H₄CMe₂C₉H₇)₂ZrCl₂ (1a, b) is reported. The isomer mixture of 1a, b was treated with different reducing agents such as sodium and n-butyllithium under various reaction conditions. In these reactions CC and CH activation and cleavage reactions were observed. In combination with methylaluminoxane (MAO) 1a, b and 3 showed low activities as homogeneous ethylene polymerization catalysts and no activities towards propylene. Compounds 2 and 3 were characterized by NMR spectroscopy and X-ray crystallography.     

Novel sandwich complexes of zirconium [C9H5(SiMe3)2](C5Me4R)ZrCl2 (R = CH3, CH2CH2NMe2): Synthesis and reduction behavior

Novel half-sandwich [C₉H₅(SiMe₃)₂]ZrCl₃ (3) and sandwich [C₉H₅(SiMe₃)₂](C₅Me₄R)ZrCl₂ (R = CH₃ (1), CH₂CH₂NMe₂ (2)) complexes were prepared and characterized. The reduction of 2 by Mg in THF lead to (η⁵-C₉H₅(SiMe₃)₂)[η⁵:η²(C,N)-C₅Me₄CH₂CH₂N(Me)CH₂]ZrH (7). The structure of 7 was proved by NMR spectroscopy data. Hydrolysis of 2 resulted in the binuclear complex ([C₅Me₄CH₂CH₂NMe₂]ZrCl₂)₂O (6). The crystal structures of 1 and 6 were established by X-ray diffraction analysis.     

Regioselectivity of reactions of vinyl- and isopropenylcyclopentadienide anions with electrophilic agents. Synthesis and crystal structures of complexes [C5H4C(Me)=CH2]ZrCl3 · 2THF and [C5Me4CH=CH2]ZrCl3 · 2THF

Regioselectivity of the reactions of lithium vinyl- and isopropenylcyclopentadienides C₅H₄C(R)=CH₂ ^-Li⁺(R = H, Me) and lithium tetramethylvinylcyclopentadienide C₅Me₄CH=CH₂ ^-Li⁺ with various electrophilic agents (Me₃SiCl, Me₃SnCl, Et₂PCl, 2-chloro-1, 3-dioxaphospholane, and MeI) was studied. Two new monocyclopentadienyl zirconium complexes, [C₅H₄C(Me) = CH₂]ZrCl₃ · 2THF and [C₅Me₄CH=CH₂]ZrCl₃ · 2THF, were synthesized. Their crystal structures were established by X-ray diffraction. The results of quantum chemical calculations for the C₅H₄C(R) = CH₂ ^- (R = H, Me) and C₅Me₄CH=CH₂ ^- anions by the DFT method (RMPW1PW91) with the 6-311+G(d, p) split valence basis set are in good agreement with experimental data on the regioselectivity of their reactions with electrophilic agents.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 390–399, February, 2005.     

A novel zirconocene/ultradispersed diamond black powder supported catalytic system for ethylene polymerization

A novel carrier of ultradispersed diamond black powder (UDDBP) was used to support metallocene catalyst. Al₂O₃ was also used as carrier in order to compare with UDDBP. Supported catalysts for ethylene polymerization were synthesized by two different reaction methods. One way was direct immobilization of the metallocene on the support, the other was adsorption of MAO onto the support followed by addition of the metallocene. Four supported catalysts Cp₂ZrCl₂/UDDBP, Cp₂ZrCl₂/Al₂O₃, Cp₂ZrCl₂/MAO/UDDBP and Cp₂ZrCl₂/Al₂O₃/MAO were obtained. The content of the zirconium in the supported catalyst was determined by UV spectroscopy. The activity of the ethylene polymerization catalyzed by supported catalyst was investigated. The influence of Al/Zr molar ratio and polymerization temperature on the activity was discussed. The polymerization rate was also observed.     

Study of the compositional heterogeneity of ethylene-1-hexene copolymers via thermal fractionation with the use of differential scanning calorimetry

The compositional heterogeneity of ethylene-1-hexene copolymers synthesized with various types of supported catalysts, namely, the titanium-magnesium catalyst TiCl₄/MgCl₂ and the zirconocene catalyst SiO₂(MAO)/Me₂Si(Ind)₂ZrCl₂, is studied via the method of successive self-nucleation-annealing (SSA) with the use of differential scanning calorimetry. On the basis of the data on the temperatures of individual peaks on SSA curves, the thickness of lamellas composed of macromolecules with a certain degree of short-chain branching is estimated. The copolymer synthesized with the zirconocene catalyst has a narrower range of fusion and does not contain large lamellas composed of molecules with a low degree of short-chain branching. With the use of the broadness index, it is shown that the copolymer synthesized with the zirconocene catalyst has a more uniform distribution of the comonomer than does the copolymer synthesized with the titanium-magnesium catalyst. For the copolymers synthesized with the titanium-magnesium catalyst, the compositional heterogeneity increases with an increase in the content of 1-hexene.     

Synthesis of oxazoline functionalized polypropene using metallocene catalysts

Using two different zirconocene/MAO catalyst systems, propene was copolymerized with the comonomers 2‐(9‐decene‐1‐yl)‐1,3‐oxazoline and 2‐(4‐(10‐undecene‐1‐oxo)phenyl)‐1,3‐oxazoline, respectively. The catalysts used were rac‐Et[Ind]₂ZrCl₂ and rac‐Me₂Si[2‐Me‐4, 5‐BenzInd]₂ZrCl₂. Up to 0.53 mol‐% oxazoline could be incorporated into polypropene. Oxazoline content, molecular weight, degree of isotacticity and melting behavior were dependent on the catalyst system, comonomer structure and comonomer concentration in the feed.     

Titanium ketimide complexes as α-olefin homo- and copolymerisation catalysts. X-ray diffraction structures of [TiCp(NCBu2)Cl2] (Cp=Ind, Cp*)

The synthesis of [TiInd(NC^tBu₂)Cl₂] and the applications of [TiCp^′(NC^tBu₂)Cl₂] (Cp^′=Ind, Cp*, Cp) as ethylene and propylene homopolymerisation catalysts, as well as its behaviour as catalysts of ethylene and 10-undecen-1-ol copolymerisation are described. The optimisation of the catalytic reactions showed that all compounds are very active homopolymerisation catalysts, particularly [TiInd(NC^tBu₂)Cl₂] that gives 123.37 × 10⁶ g/(molTi [E] h) and 50.77 × 10⁶ g/(molTi [P] h) of linear polyethylene and atatic polypropylene, respectively. The less active homopolymerisation catalyst, [TiCp(NC^tBu₂)Cl₂], is the most effective ethylene/10-undecen-1-ol copolymerisation catalyst, leading to the highest degree of polar monomer incorporation. The polymers obtained were characterised by NMR and DSC. The molecular structures of [TiCp^′(NC^tBu₂)Cl₂] (Cp^′=Ind, Cp*) were determined by X-ray diffraction studies.     

Density functional theory study of the interaction of CP2*ZrCH 3+ (Cp* = C5H5, C5Me5, and C13H9) with ethylene molecule

Density functional theory was used to study gas-phase reactions between the Cp₂*ZrMe⁺ cations, where Cp* = C₅H₅ (1), Me₅Cp = C₅Me₅ (2), and Flu = C₁₃H₉ (3), and the ethylene molecule, Cp₂*ZrMe⁺ + C₂H₄ → Cp₂*ZrPr⁺ → Cp₂*ZrAllyl⁺ + H₂. The reactivity of the Cp₂*ZrMe⁺ cations with respect to the ethylene molecule decreased in the series 1 > 3 ≈ 2. Substitution in the Cp ring decreased the reactivity of the Cp₂*ZrMe⁺ cations toward ethylene, in agreement with the experimental data on the comparative reactivities of complexes 1 and 3. The two main energy barriers along the reaction path (the formation of the C-C bond leading to the primary product Cp₂*ZrPr⁺ and hydride shift leading to the secondary product Cp₂*Zr(H₂)Allyl⁺) vary in opposite directions in the series of the compounds studied. For Flu (3), these barriers are close to each other, and for the other compounds, the formation of the C-C bond requires the overcoming of a higher energy barrier. A comparison of the results obtained with the data on the activity of zirconocene catalysts in real catalytic systems for the polymerization of ethylene led us to conclude that the properties of the catalytic center changed drastically in the passage from the model reaction in the gas phase to real catalytic systems.