ansa-Metallocene (R-Ph)2C(Cp)(Ind)MCl2 with electron withdrawing substituents on phenyl groups for olefin polymerization

The new ansa-complexes (R-Ph)₂C(Cp)(Ind)MCl₂ (R = CF₃, F, Cl; M = Ti, Zr or Hf) were synthesized from the reaction of dilithium salt of the corresponding ligands with appropriate group 4 metal halides. They were tested for ethylene homopolymerization and copolymerization in the presence of methylaluminoxane (MAO) at various ethylene pressures and temperatures. In the case of zirconocenes, complexes 2 (R = CF₃) and 8 (R = Cl) demonstrated much higher catalytic activity than complexes 10 (Ph₂C(Cp)(Ind)ZrCl₂) and 5 (R = F) in ethylene polymerization. The same trend was observed in titanocenes and hafnocenes. The electronic and geometric effects of substituents at the phenyl group on the polymerization activity were easily noticed. For the ethylene/1-hexene or 1-octene copolymerization, 2 also showed the highest catalytic activity, and the copolymers from complex 8 possessed the highest 1-hexene and 1-octene contents.     

Preparation of titanocene and zirconocene dichlorides bearing bulky 1,4-dimethyl-2,3-diphenylcyclopentadienyl ligand and their behavior in polymerization of ethylene

New metallocene dichlorides [η⁵-(1,4-Me₂-2,3-Ph₂-C₅H)₂TiCl₂] (2), [η⁵-(1,4-Me₂-2,3-Ph₂-C₅H)₂ZrCl₂] (3) and [η⁵-(1,4-Me₂-2,3-Ph₂-C₅H)η⁵-(C₅H₅)ZrCl₂] (4) were prepared from lithium salt of 1,4-dimethyl-2,3-diphenylcyclopentadiene (1) and [TiCl₃(THF)₃], [ZrCl₄] and [η⁵-(C₅H₅)ZrCl₃(DME)], respectively. Compounds 2-4 were characterized by NMR spectroscopy, EI-MS and IR spectroscopy, and the solid state structure of 3 was determined by single crystal X-ray crystallography. The catalytic systems 3/MAO and 4/MAO were almost inactive in polymerization of ethylene at 30-50 °C, however, they exhibited high activity at temperature 80 °C. The catalyst formed from 2 and excess of MAO was practically inactive at all temperatures.     

Novel layered calcosilicate-immobilized iron-based diimine catalyst for ethylene polymerization

A novel layered calcosilicate (CAS-1) was employed to immobilize an iron-based diimine catalyst 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine iron chloride (I) onto it to form a supported catalyst (CC) for the first time. The crystal structure of CAS-1 was determined by X-ray crystallographic analysis in addition to SEM characterization. The CC-catalyzed ethylene polymerization exhibited good catalytic activities with either co-catalyst methylaluminoxane (MAO) or triethylaluminum (TEA). The resulting polyethylenes possessed not only higher molecular weight, melting temperature (T_m), and decomposition onset temperature (T_onset) than those obtained with its homogeneous counterpart, but also a unique morphology.     

A novel alkenyl-substituted ansa-zirconocene complex with dual application as olefin polymerization catalyst and anticancer drug

The alkenyl substituted fulvene compound, (C₅H₄)CMe(CH₂CH₂CHCMe₂) (1), reacts with one equivalent of LiMe to give the lithium derivative Li{C₅H₄(CMe₂CH₂CH₂CHCMe₂)} (2). The reaction of 2 with Me₂Si(C₅Me₄H)Cl gave the ansa-ligand precursor Me₂Si(C₅Me₄H)(C₅H₄(CMe₂CH₂CH₂CHCMe₂)) (3), which after the subsequent reaction with 2 equivalents of LiBuⁿ yielded the dilithium salt Li₂{Me₂Si(C₅Me₄)(C₅H₃(CMe₂CH₂CH₂CHCMe₂))} (4). The alkenyl-substituted zirconocene complex [Zr{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₃(CMe₂CH₂CH₂CHCMe₂))}Cl₂] (5) was synthesized by the equimolar reaction of 4 and ZrCl₄. 5 was characterized by spectroscopic methods and by single crystal X-ray diffraction studies. The zirconocene compound 5 has been tested as a catalyst in the polymerization of ethylene at different temperatures and Al:Zr ratios, and also in the co-polymerization of ethylene and 1-octene, observing modest co-monomer incorporations. In addition, the cytotoxic activity of 5 was tested against tumour cell lines 8505C anaplastic thyroid cancer, A253 head and neck tumour, A549 lung carcinoma, A2780 ovarian cancer and DLD-1 colon carcinoma. Complex 5 showed the best cytotoxic activity on A2780 ovarian cancer (IC₅₀ value of 36.8 ± 5.9 μM). This represents the highest reported cytotoxic activity of a zirconocene complex on A2780 ovarian cancer. In addition, the cytotoxic activities of 5, have been compared with those obtained using cisplatin.     

Synthesis of phenylene–silylene–ethylene polymers via transition metal complex catalyzed hydrosilylation polymerization

New phenylene–silylene–ethylene polymers have been successfully synthesized using platinum–divinylsiloxane or rhodium and iridium siloxide complex‐catalysed polyhydrosilylation of divinylsubstituted carbosilanes with dihydrocarbosilanes or intermolecular hydrosilylation of new hydrovinylcarbosilane. Polycarbosilanes have been obtained with high molecular weights. They seem to be potential parent substances for future applications as preceramic and membrane materials. Copyright © 2005 John Wiley & Sons, Ltd.     

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.     

Zirconium complexes in homogeneous ethylene polymerization

This article reviews the recent progress of zirconium complexes for ethylene polymerization. Zirconium complexes are one of the most important types of catalysts for homogeneous ethylene polymerization. Polymerization behavior and polymer structure can be adjusted through the balancing of ligand structure. We surveyed the zirconium complexes synthesized from 2006 to early 2009 and summarize their comparative catalytic activities. Generally, the main factor observed is the steric bulk which on increasing reduces the catalytic activity. Electron count, electronic cloud, and inductive effect also influence the catalytic activity.     

The effect of cocatalysts on the oligomerization and cyclization of ethylene catalyzed by zirconocene complexes

Under certain conditions (150°C, P(C₂H₄)=1.4 MPa), the oligomerization of ethylene catalyzed by Cp₂ZrCl₂/EAO (ethylaluminoxane), Et₃Al or (i-Bu)₃Al afforded methylenecyclopentane (MCP) along with chain oligomers. The nature of cocatalysts and the Al/Zr ratios as well as the hydrolysis extent of Et₃Al have tangible effects on the selectivity of the cyclic oligomer. With Et₃Al as cocatalyst under optimal conditions, the oligomerization of ethylene gave MCP and C₄–C₁₀ chain olefins in a ratio of 45/55.

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二甲基二茂锆化合物(1,2-Ph2-4-MeCp)2 ZrMe2的合成及催化乙烯聚合反应研究

在惰性气氛下, 用2 mol甲基锂处理二(1,2-二苯基-4-甲基环戊二烯基)二氯化锆, 合成了大立体位阻的二甲基二茂锆化合物[(1,2-Ph2-4-MeCp)2ZrMe2]. 经元素分析、 核磁共振氢谱、 碳谱和X射线晶体衍射分析, 确定了该化合物的结构. 经Al( i Bu)3/Ph3C+B(C6F5)-4活化, 该化合物催化乙烯聚合反应显示出较高的催化活性, 生成高分子量及高熔点聚乙烯. 该体系的特点是在较低的n(Al)/n(Zr)比下即可有效地催化乙烯聚合.     

Polymerization of ethylene catalyzed by titanocene(iii) -b-diketonate complex and MMAO

Ethylene polymerizations were performed with a catalytic system composed of titanocene(III)-β-diketonate complex such as [Cp2Ti(III)(1-benzoylacetonato)] or [Cp2Ti(III)(dibenzoylmethanato)] and MMAO. These catalysts are active for the polymerization of ethylene to give high-density polyethylene with high molecular weight. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis of anilinonaphthoquinone-based nickel complexes and their application for olefin polymerization

A series of anilinonaphthoquinone-based nickel complexes, Ni(C₁₀H₅O₂NAr)(Ph)(PPh₃) (Ar = C₆H₃-2,6-Me (1c); Ar = C₆H₂-2,4,6-Me (2c); Ar = C₆H₃-2,6-Et (3c)), were synthesized and the structures of 1c-3c were confirmed by single crystal X-ray analyses. The anilinonaphthoquinone-ligated nickel complexes activated with B(C₆F₅)₃ showed high activities for ethylene polymerization at 40 °C under atmospheric pressure of ethylene and gave polyethylene with long chain branches and short chain branches. The activity of these systems was decreased by lowering polymerization temperature accompanied by increase in molecular weight. The number of the chain branches was also decreased with lowering polymerization temperature and increasing the bulkiness of the ligand.     

Titanium complexes bearing bidentate benzimidazole-containing ligands and their behavior in ethylene polymerization

A series of potentially bidentate benzimidazolyl ligands of the type (Bim)CH₂D (where Bim = benzimidazolyl and D = NMe₂L1, NEt₂L2, NPrⁱ₂L3, OMe L4 and SMe L5) has been reacted with Ti(NMe₂)₄ to give five- and six-coordinate Ti(IV) complexes of the type [(Bim)CH₂D]Ti(NMe₂)₃ and [(Bim)CH₂D]₂Ti(NMe₂)₂, respectively. The X-ray structures of [(Bim)CH₂OMe]Ti(NMe₂)₃, [(Bim)CH₂NMe₂]₂Ti(NMe₂)₂ and [(Bim)CH₂OMe)]₂Ti(NMe₂)₂ are reported along with an evaluation of their behavior in ethylene polymerization.     

Polymer‐supported zirconocene catalyst for ethylene polymerization

The use of crosslinked poly(styrene‐co‐4‐vinylpyridine) having functional groups as the support for zirconocene catalysts in ethylene polymerization was studied. Several factors affecting the activity of the catalysts were examined. Conditions like time, temperature, Al/N (molar ratio), Al/Zr (molar ratio), and the mode of feeding were found having no significant influence on the activity of the catalysts, while the state of the supports had a great effect on the catalytic behavior. The activity of the catalysts sharply increased with either the degree of crosslinking or the content of 4‐vinylpyridine in the support. Via aluminum compounds, AlR₃ or methylaluminoxane (MAO), zirconocene was attached on the surface of the support. IR spectra showed an intensified and shifted absorption bands of C N in the pyridine ring, and a new absorption band appeared at about 730 cm⁻¹ indicating a stable bond Al N formed in the polymer‐supported catalysts. The formation of cationic active centers was hypothesized and the performance of the polymer‐supported zirconocene was discussed as well. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 37–46, 1999     

Syndiospecific living polymerization of 4‐methylstyrene and styrene with (trimethyl)pentamethylcyclopentadienyltitanium/tris(pentafluorophenyl)borane/trioctylaluminum catalytic system

The polymerizations of styrene and 4‐methylstyrene (4MS) with a half‐metallocene type catalytic system composed of (trimethyl)pentamethylcyclopentadienyltitanium (Cp*TiMe₃), trioctylaluminum (AlOct₃), and tris(pentafluorophenyl)borane [B(C₆F₅)₃] were investigated at ?25 °C. The addition of AlOct₃ as a third component of the catalytic system is effective both to promote the syndiospecific polymerization and to inhibit the nonstereospecific polymerization at the low‐temperature region. The use of AlOct₃ was also effective to eliminate the chain transfer reaction to alkylaluminum. The number‐average molecular weights (M_n's) of poly(4MS) or polystyrene increased proportionally with increasing monomer conversion. The molecular weight distribution (MWD) of polymer stayed narrow [M_w/M_n = ～ 1.1 for poly(4MS) and M_w/M_n = ～ 1.5 for polystyrene]. It was thus concluded that the polymerizations of the styrenic monomers with Cp*TiMe₃/B(C₆F₅)₃/AlOct₃ catalytic system proceeded under living fashion at ?25 °C. The living random copolymerization behaviors of styrene and 4MS were also confirmed. The ¹³C NMR analysis clarified that each of the homopolymers and random copolymers obtained in this work had highly syndiotactic structure. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3692–3706, 2001     

Titanium complexes with novel triaryl-substituted phosphinimide ligands: Synthesis, structure and ethylene polymerization behavior

A series of titanium phosphinimide complexes [Ph₂P(2-RO-C₆H₄)]₂TiCl₂ (7, R = CH₃; 8, R = CHMe₂) and [PhP(2-Me₂CHO-C₆H₄)][THF]TiCl₃ (9) have been prepared by reaction of TiCl₄ with the corresponding phosphinimines under dehalosilylation. The structure of complex 9 has been determined by X-ray crystallography, and a solvent molecule THF was found to be coordinated with the central metal and the Ti-O bond was consistent with the normal Ti-O (donor) bond length. The complexes 7 and 8 displayed inactive to ethylene polymerization, and the complex 9 displayed moderate activity in the presence of modified methylaluminoxane (MMAO) or i-Bu₃Al/Ph₃CB(C₆F₅)₄, and this should be partly attributed to coordination of THF with titanium and the steric effect of two iso-propoxyl. And catalytic activity up to 32.2 kg-PE/(mol-Ti h bar) was observed.     

Use of V and V–Cr catalysts interchanged in “Y” zeolites for the polymerization of ethylene

Ethylene polymerization has been studied in the presence of catalyst based on vanadium or vanadium-chromium supported on a zeolite HY. The effect of vanadium over chromium has been investigated as a function of the sequence of exchange of metals on the support and metal contents. Both effects were investigated in relation to the characteristics of the polyethylene (PE) obtained. Low activity has been found for the V ( II ) zeolite HY catalyst. Moreover, vanadium acts either as an inhibitor or as a promoter for the polymerizing activity of the Cr ( III )/zeolite catalyst, depending on the preparation method. © 1994 John Wiley & Sons, Inc.     

Substituent effect of bisindenyl zirconene catalyst on ethylene/1-hexene copolymerization and propylene polymerization

Nonbridged bis-substituted indenyl zirconene complexes were used as the catalysts for ethylene/1-hexene copolymerization and propylene polymerization. The complicated “comonomer effect” on the activity of ethylene/1-hexene copolymerization was observed. The effect also worked on the incorporation of comonomer. The number and the position of the substituents were important for the copolymerization behavior and the microstructure of the resultant copolymer as well as for propylene polymerization.     

Synthesis, structure and ethylene polymerization behavior of titanium phosphinoamide complexes

(Phosphinoamide)(cyclopentadienyl)titanium(IV) complexes of the type Cp*TiCl₂(η²-Ph₂PNR) [Cp*=C₅Me₅; R = t-Bu (2a), R = n-Bu (2b), R = Ph (2c)] have been prepared by the reaction of Cp*TiCl₃ with the corresponding lithium phosphinoamides. The structure of Cp*TiCl₂(η²-Ph₂PN^tBu) (2a) and Cp*TiCl₂(η²-Ph₂PNPh) (2c) have been determined by X-ray crystallography. These complexes exhibited moderate catalytic activities for ethylene polymerization in the presence of modified methylaluminoxane (MMAO). Catalytic activity of up to 2.5 × 10⁶ g/(mol Ti h) was observed when activated by i-Bu₃Al/Ph₃CB(C₆F₅)₄.     

Tris(pyrazolyl)methane–chromium(III) complexes as highly active catalysts for ethylene polymerization

Reaction of complex CrCl₃(THF)₃ with the tris(pyrazolyl)methane ligands, HC(Pz)₃, HC(3,5-Me₂Pz)₃ and their substituted derivatives RC(Pz)₃ (R = Me, CH₂OH, CH₂OSO₂Me) in THF lead to the formation of neutral complexes of the types [RC(Pz)₃CrCl₃] and [RC(3,5-Me₂Pz)₃CrCl₃]. After reaction with methylalumoxane (MAO) these complexes are active in the polymerization of ethylene. The substituent on the methane central carbon atom of the ligand has some influence in polymerization behavior. This compounds present higher activities than similar chromium complexes, in the ethylene polymerization reaction.     

Effect of experimental conditions on ethylene polymerization with in‐situ‐supported metallocene catalyst

Ethylene polymerization was carried out with a novel in‐situ‐supported metallocene catalyst that eliminates the need for a supporting step before polymerization. The influence of the metallocene amount, aluminum to zirconium mole ratio, temperature, pressure, and cocatalyst type on polymerization kinetics and molecular weight distribution of the produced polyethylene was studied. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1803–1810, 2000