“茂后”烯烃聚合催化剂

总结了近几年发展起来的新一代烯烃聚合催化剂———“茂后”催化剂,对“茂后”催化剂进行分类并对催化剂的结构、性能、催化烯烃聚合机理进行了评述．参考文献３３篇．     

茂金属/硼化合物烯烃聚合催化体系研究进展

本文介绍了茂金属? 硼化合物催化体系最新研究进展, 从催化体系的活性中心、聚合机理、新的茂金属及硼化物体系、它们对烯烃及极性单体的催化聚合等方面作了较详细阐述。     

四（五氟化苯基）卟啉氯化铁选择催化氧化超临界丙烷的反应机理

 以BHT为自由基捕捉剂，研究了四（五氟化苯基）卟啉氯化铁（Ⅲ）将超临界丙烷高选择性催化氧化为丙醇的反应机理．通过GC－MS分析发现，反应产物中有PBHT，故可认为在超临界丙烷氧化反应过程中有丙基自由基存在，初步推断反应涉及自由基机理．同时发现高浓度BHT抑制反应，低浓度BHT促进反应的现象，而以戊烷为底物时没有促进作用．这是由于BHT的位阻效应所致．并对BHT存在时超临界丙烷氧化反应机理进行了初步的推断．     

吡啶亚胺(胺)钒烯烃聚合催化剂

设计合成了一系列以吡啶二亚胺、吡啶胺-亚胺和吡啶二胺为螯合配体的三价钒配合物2a2e, 并通过红外和元素分析等技术手段对其进行了结构表征。 在助催化剂和再生活化剂的存在下, 这些催化剂展示出了高活性和良好的高温稳定性。 得到高相对分子质量、单峰分布聚乙烯表明聚合体系为单活性中心。 以吡啶二胺为螯合配体的配合物2e(2, 6-bis[2, 6-(ⁱPr)₂PhNC(Me)]₂(C₅H₃N)VCl)在50 ℃下显示出的活性高达6.96 kg PE/mmol_V·h, 且在70 ℃时仍保持高的催化活性, 这表明双阴离子吡啶二胺能更好的保护催化活性中心。 此外, 这类三价钒催化剂能高活性催化乙烯-降冰片烯及乙烯-己烯共聚, 在温和条件下即可得到较高单体插入率(降冰片烯37.3%, 己烯4.8%)的共聚物。     

Supported Zr-and Hf-cene Catalysts for Propylene Polymerization

The supported metallocene catalysts were obtained on the layered silicate montmorillonite (MMT), using AlMe₃ and AliBu₃ for synthesis of alkylaluminoxane directly on a support surface, followed by metallocene supporting. It was shown that the MMT-H₂O/AliBu₃ forms with ansa-Zr-cenes of C₁ and C₂-symmetry the significantly more active supported metal-alkyl complexes in propene polymerization, than MMT-H₂O/AlMe₃. The MMT-H₂O/AliBu₃ is the effective activator of the ansa-Hf-cenes, in contrast to MAO and MMT-H₂O/AlMe₃, giving the high active supported catalysts for synthesis of isotactic and elastic polypropene. The character of influence of metallocene fixation on support on the isotactic pentad [mmmm] content in polymer, compared to homogeneous analogues, depends on the metallocene nature. The introduction of borate Ph₃CB(C₆F₅)₄ in the case of both Zr-cene and Hf-cene catalysts increases significantly the activity at the reduced ratio of Al/Zr, Hf (100–500 instead of 2000–3000) and stabilizes the catalytic complexes.     

Latent Olefin Metathesis Catalysts for Polymerization of DCPD

Summary: Advances in design of latent ruthenium phenylindenylidene catalysts bearing salicylaldimine ligands for ring-opening metathesis polymerization are described. The presence of the substituents in ortho position in N-aryl ring of salicylaldimine ligand has been found to be the main factor determining the catalyst stability. The best of the studied catalysts after acid activation offers activity comparable to that of the dichloride systems in ring-opening metathesis polymerization of DCPD, while maintaining very high stability in the monomer solution.     

A Sterically Hindered Zirconocene Complex (1,2-Ph2C5H3)2ZrCl2:Synthesis, Structure and Properties as Olefin Polymerization Catalyst

SinceKaminskyeIal.discoveredthehighlyactivezirconocenedich1oride/methyl-aluminoxane(MAO)catalyticsystemforolefinpolymerization',intensiveresearchworkhasbeenfocusedondevelopingnewgroup4metal1ocenecatalystsforimprovingcatalystactivitiesandpolymerproperties"'.Inthedevelopmentofnewmetallocenecatalystsystems,liganddesignandmodificationhaveplayedanimportantrole.lthasbeenknownthatevenminormodificationofagivenligandframeworkcouldresultinsignificantchangesincatalystactivitiesandpolymerproperties'.Int…     

Aqueous cationic olefin polymerization using tris(pentafluorophenyl)gallium and aluminum

Tris(pentafluorophenyl)gallium ( 3 ) and aluminum ( 7 ) are active coinitiators for the production of medium‐high molecular weight (MW) polymers of styrene and isobutene (IB) under aqueous reaction conditions. Strong Brønsted acids formed in situ by reaction of these coinitiators with background moisture present in the monomer droplet ( 5 and 8 , respectively) are believed to be responsible for inducing cationic polymerization of these monomers. Of the two, 7 is the most active for IB polymerization in both aqueous media and anhydrous aliphatic solvents. These results are in contradistinction to tris(pentafluorophenyl)boron ( 2 ), which is incapable of polymerizing IB in aqueous or aliphatic media. The MWs of the polyisobutenes (PIBs) produced under aqueous conditions by either coinitiator greatly exceed those formed under similar reaction conditions by the strongly acidic chelating diborane (1,2‐C₆F₄[B(C₆F₅)₂]₂, 1 ) or diborole (1,2‐C₆F₄[9‐BC₁₂F₈]₂, 6 ). Both 3 and 7 are readily synthesized from the corresponding Group 13 halide compounds in conjunction with bis(pentafluorophenyl)zinc ( 4 ). Aqueous polymerization of IB dissolved in aliphatic solvents with 3 or 7 can yield PIBs with relatively narrow polydispersities. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

(η5-Pentamethylcyclopentadienyl)trimethyltitanium as a precursor for the syndiospecific polymerization of styrene

An equimolar mixture of Cp*Ti(CH₃)₃ (2) and Ph₃C⁺[B(C₆F₅)₄]^? (1) forms a highly active and syndioselective catalyst for the polymerization of styrene, producing 96% syndiotactic polystyrene (PS) at an activity of 0.91 × 10⁷ g PS (mol Ti)^?1 (mol styrene)^?1 h^?1. Both activity and syndioselectivity can be increased using tri–isobutylaluminum (TIBA) to scavenge the system. ESR measurements indicate that the polymerization proceeds via titanium(IV) intermediates. Catalysts derived from 2/methylaluminoxane (MAO) as well as Cp*TiCl₃/MAO also function as syndioselective styrene polymerization catalysts, but are less active than the ‘cationic’; system derived from 1 and 2.     

Preparation of Titania from Tetrakis(diethylamino)titanium via Hydrolysis

The conversion of tetrakis(diethylamino)titanium (Ti(NEt₂)₄) into titania via either a combination of hydrolysis (Ti(NEt₂)₄ : THF : H₂O = 1 : 10 : x, x = 2, 4, 10) at ambient conditions and calcination (method A) or hydrolysis in a water-tetrahydrofuran (THF) mixture (Ti(NEt₂)₄ : THF : H₂O = 1 : 10 : 100) at reflux (method B) was investigated. Titanium tertiary butoxide (Ti(O ^t Bu)₄) was also used as a substitute for Ti(NEt₂)₄. The hydrolysis via method A resulted in the formation of amorphous solids containing organics. Thermal analyses showed that the hydrolysis products showed mass losses up to 500°C probably due to the presence of diethylamine (Et₂NH) formed via the hydrolysis of Ti(NEt₂)₄ in the hydrolysis products, while a mass loss of the hydrolysis product from Ti(O ^t Bu)₄ was completed up to about 200°C. After calcination at 600°C, anatase or a mixture of anatase and rutile was obtained. The crystallization behavior of the hydrolysis products from Ti(NEt₂)₄ was different from that of the hydrolysis product from Ti(O ^t Bu)₄. The hydrolysis via method B gave only an amorphous material from Ti(NEt₂)₄, while a crystalline titania (anatase and brookite) formed from Ti(O ^t Bu)₄.     

Influences of steric bulkiness in hydrotris(pyrazolyl)borate ligands on ethylene polymerization reaction

Manganese(II) complex catalysts with hydrotris(pyrazolyl)borate ligands have been examined on their catalytic performance in ethylene polymerization and ethylene/1‐hexene copolymerization. The activities of [Mn(L6)(Cl)(NCMe)] ( 1 ) and [Mn(L10)(Cl)] ( 2 ) activated by Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] for ethylene polymerization go up to 326 and 11 kg mol (cat^?1) h^?1, respectively, (L6^? = hydrotris(3‐phenyl‐5‐methyl‐1‐pyrazolyl)borate anion, L10^? = hydrotris(3‐adamantyl‐5‐isopropyl‐1‐pyrazolyl)borate anion). In particular, for ethylene/1‐hexene copolymerization, complex 1 gives high‐molecular‐weight poly(ethylene‐co‐1‐hexene)s with the highest M_w of 439,000 in manganese olefin polymerization catalyst systems. Moreover, the 1‐hexene incorporation by complex 1 seems more efficient than that by [Mn(L3)(Cl)] ( 4 ) (L3^? = hydrotris(3‐tertiary butyl‐5‐isopropyl‐1‐pyrazolyl)borate anion). In this work, we demonstrated that the coordination geometry and coordination number are also important factors for ethylene polymerization reaction as well as steric hindrances and ligand frameworks in our manganese(II) catalysts. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5720–5727, 2009     

Improved Molecular Weight Control in Ring‐Opening Metathesis Polymerization (ROMP) Reactions with Ru‐Based Olefin Metathesis Catalysts Using N Donors and Acid: A Kinetic and Mechanistic Investigation

The effect of the addition of H₃PO₄ on the ROMP activity of cyclooctene (COE) with first‐ [Cl₂(PCy₃)₂Ru?CHPh] and second‐generation [(H₂IMes)Cl₂(PCy₃)Ru?CHPh] Grubbs’ catalysts 1 and 4 (Cy=cyclohexyl, Ph=phenyl, Mes=2,4,6‐trimethylphenyl (mesityl)), their inhibited mixtures with 1‐methylimidazole (MIM), as well as their isolated bis‐N,N′‐dimethylaminopyridine (DMAP) derivatives [Cl₂(PCy₃)(DMAP)₂Ru?CHPh)] ( 5 b ) and [Cl₂(H₂IMes)(DMAP)₂Ru?CHPh] ( 7 b ) (DMAP=dimethylaminopyridine), a novel catalyst, has been investigated. The studies include the determination of their initiation rates, as well as a determination of the molecular weights and molecular weight distributions of the polymers obtained with these catalysts and catalyst mixtures from the exo‐7‐oxanorbornene derivative 11 . The structure of catalyst 7 b was confirmed by means of X‐ray diffraction. All N‐donor‐bearing catalysts or N‐donor‐containing catalyst mixtures not only exhibited elevated activity in the presence of acid, but also increased initiation rates. Using the reversible inhibition/activation protocol with MIM and H₃PO₄ enabled us to conduct controlled ROMP with catalyst 4 producing the isolated exo‐7‐oxanorbornene‐based polymer 12 with predetermined molecular weights and narrow molecular weight distributions. This effect was based on fast and efficient catalyst initiation in contrast to the parent catalyst 4 . Hexacoordinate complex 5 b also experienced a dramatic increase in initiation rates upon acid‐addition and the ROMP reactions became well‐controlled in contrast to the acid‐free reaction. In contrast, complex 7 b performs well‐controlled ROMP in the absence of acid, whereas the polymerization of the same monomer becomes less controlled in the presence of H₃PO₄. The closer evaluation of catalysts 5 b and 7 b demonstrated that their initiation rates exhibit a linear dependency on the substrate concentration in contrast to catalysts 1 and 4 . As a consequence, their initiation rates are determined by an associative step, not a dissociative step as seen for catalysts 1 and 4 . A feasible associative metathesis initiation mechanism is proposed.     

Polymerization of methyl methacrylate by metallocene imido complexes and tris(pentafluorophenyl)alane

The polymerization of methyl methacrylate (MMA) was investigated with tris(pentafluorophenyl)alane [Al(C₆F₅)₃] and four metallocene imido complexes that varied in the complex symmetry/chirality, metal, and R group in the ?NR moiety, as well as a zirconocene enolate preformed from the imido zirconocene and MMA. This study examined four aspects of MMA polymerization: the effects of the metallocene imido complex structure on the polymerization activity and polymer tacticity, the degree of polymerization control, the elementary reactions of the imido complex with Al(C₆F₅)₃ and MMA, and the polymerization kinetics and mechanism. There was no effect of the imido complex symmetry/chirality on the polymerization stereochemistry; the polymerization followed Bernoullian statistics, producing syndiotactic poly(methyl methacrylate)s with moderate (～70% [rr]) to high (～91% [rr]) syndiotacticity, depending on the polymerization temperature. Polymerization control was demonstrated by the number‐average molecular weight, which increased linearly with an increase in the monomer conversion to 100%, and the relatively small and insensitive polydispersity indices (from 1.21 to 1.17) to conversion. The reactions of the zirconocene imido complex with Al(C₆F₅)₃ and MMA produced the parent base‐free imido complex and the [2 + 4] cycloaddition product (i.e., zirconocene enolate), respectively; the latter product reacted with Al(C₆F₅)₃ to generate the active zirconocenium enolaluminate. The MMA polymerization with the metallocene imido complex and the alane proceeded via intermolecular Michael addition of the enolaluminate to the alane‐activated MMA involved in the propagation step. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3132–3142, 2003     

Effects of tris(pentafluorophenyl)borane on the activation of the Ni(II)-based catalyst in the addition polymerization of norbornene

The activity of the transition metal complex, such as Ni(2-ethyl hexanoate)₂ (1), Co(2-ethyl hexanoate)₂ (2), TiCl₄ (3), or CpTiCl₃ (4) (Cp = cyclopentadiene), in combination with MAO (methylaluminoxane), was investigated in the polymerization of norbornene. The Ni(II) complex 1 with MAO showed moderate activity to give 20.8 kg_polymer/mol_Ni h, while the other three complexes 2-4 with MAO just showed trivial activity. Effects of the Lewis acids on the activation of the catalyst of 1/MAO were examined. The employment of B(C₆F₅)₃ with 1/MAO significantly enhanced the activity to give up to around 133 kg_polymer/mol_Ni h. The use of other borane compounds, such as B(C₆H₅)₃ and BEt₃, or the stronger electron acceptor BF₃ · OBu₂, with 1/MAO in place of B(C₆F₅)₃ clearly showed the main functions of B(C₆F₅)₃. The high Lewis acidity of B(C₆F₅)₃ enabled it to develop matured active complexes, thus enhancing the activity. Several Ni(II) complexes were employed to determine whether their activity was comparable to that of complex 1 in norbornene polymerization. The study of the ¹H and ¹³C NMR spectra of the polynorbornene produced with 1/B(C₆F₅)₃/MAO showed that the initiation of addition polymerization occurred through the insertion of the exo face of the norbornene into the active complex. Effects of the variation in the polymerization variables, such as the levels of B(C₆F₅)₃ and MAO, temperature, and solvent, on the polymerization were discussed.     

Inclusion Complexes of Cyclodextrins with Tetrakis(4-carboxyphenyl)porphyrin and Tetrakis(4-sulfonatophenyl)porphyrin in Aqueous Solutions

In neutral and alkaline solutions, tetrakis(4-carboxyphenyl)porphyrin (TCPP) and tetrakis(4-sulfonatophenyl)porphyrin (TSPP) form 1:1 and 2:1 host–guest inclusion complexes with -cyclodextrin (-CD), -cyclodextrin (-CD), and 6-deoxy-6-diethylamino--CD (DEA--CD), except for DEA--CD in alkaline solution. On the other hand, TCPP and TSPP form only 1:1 inclusion complexes with 6-deoxy-6-dihexylamino--CD (DHA--CD). The limited solubilities of DEA--CD in alkaline solution and DHA--CD are likely responsible for no observation of the 2:1 inclusion complex containing DEA--CD in alkaline solution and that containing DHA--CD. The equilibrium constants (Ks) of TCPP and TSPP for the formation of the inclusion complexes have been estimated from the absorption and/or fluorescence intensity changes in neutral and alkaline solutions. The K₂ values, which are the equilibrium constants for the formation of the 2:1 host–guest inclusion complex from the 1:1 inclusion complex, are about one tenth the corresponding K₁ values, except for the -CD–TSPP system in alkaline solution. In neutral solution, where DEA--CD and DHA--CD are in protonated forms, the electrostatic force operates between DEA--CD (DHA--CD) and TCPP (TSPP), leading to the greater K values than those in alkaline solution, where DEA--CD and DHA--CD exist as neutral species.     

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.     

Living Polymerization of Propene with Alkyltitanium-Based Catalysts

Living polymerization of propene with alkyltitanium-based catalysts is described with emphasis on the role of the activators employed. (¹ : ³-tert-Butyl(dimethylfluorenylsilyl)amido)dimethyltitanium activated by tris(pentafluorophenyl)borane (B(C₆F₅)₃) catalyzes the living polymerization at -50 °C. The use of dried methylaluminoxane (MAO) in place of B(C₆F₅)₃ raises the living polymerization temperature to 0 °C and improves the syndiospecificity. A chelating diamide dimethyltitanium activated by dried modified MAO (MMAO) catalyzes the living polymerization at 0 °C to give a statistically atactic polymer. The heterogenization of the living systems is attempted by supporting MAO, MMAO and dried MMAO on SiO₂ as solid activators.     

Isoselective Ring-opening Polymerization of Racemic Lactide Catalyzed by N-heterocyclic Olefin/(Thio)urea Organocatalysts

The isoselective ring-opening polymerization of racemic lactide was achieved by combining N-heterocyclic olefin(NHO) with mono(thio)ureas or bis(thio)ureas as catalytic systems. The polymerization process shows high stereoselectivity, controllability and reactivity,delivering multi-block isotactic polylactides with high chain-end fidelity and narrow molecular weight distributions. The enhancement of catalytic performance was observed in the following order: bisthiourea(DTU) monothiourea(TU) bisurea(DU) urea(U). The highest Pm(probability of forming a meso dyad) = 0.91 was observed at-70 °C when using NHO/U1 catalytic system and the high stereoselectivity was attributed to chain-end control mechanism.     

B(C6F5)3在有机化学及高分子化学中的应用研究进展

B(C6F5)3与传统的Lewis酸相比,具有化学性质稳定、酸性强、使用方便等优点,被称为非传统的Lewis酸。B(C6F5)3的应用领域已经从最初的烯烃聚合共催化剂向有机化学及高分子化学的其它各个领域发展。B(C6F5)3催化的反应与传统Lewis酸催化的反应在反应机理及反应结果上均有很大的不同。本文主要综述B(C6F5)3近年来在有机化学及高分子化学中的应用研究成果。     

Ethylene (Co)Polymerization with Metallocene Catalysts Encapsulated in Gel‐Type Poly(styrene‐co‐divinylbenzene) Beads

Gel‐type poly(styrene‐co‐divinylbenzene) beads (PS bead) were used as a carrier to encapsulate metallocene catalysts through a simple swelling‐shrinking procedure. The catalytic species were homogeneously distributed in the PS bead particle. The catalyst exhibited high and stable ethylene polymerization and ethylene/1‐hexene copolymerization activity affording uniform spherical polymer particles (1 mm). Polymerization rate profiles exhibited slow initiation and stable increase in polymerization activity with time.