Alkylidenverbrückte dissymmetrische zweikernige Metallocenkomplexe als Katalysatoren für die Ethylenpolymerisation

The synthesis is described of dissymmetric alkylidene bridged dinuclear metallocene complexes of titanium, zirconium and hafnium and some of the corresponding mononuclear reference complexes. The influence of structural parameters on the polymerization behaviour of the MAO activated complexes is systematically investigated for homogeneous ethylene polymerization. The dinuclear catalysts show higher polymerization activities than a mixture consisting of analogous mononuclear reference catalysts. The polyethylenes obtained from dinuclear complexes have higher polydispersities than those that were produced with mononuclear complexes.     

Hexene-1 polymerization by homogeneous zirconocene and heterogeneous-supported TiCl3 catalysts

MgCl₂-supported TiCl₃ catalysts, with and/or without electron donor modifier (internal B_i or external B_e), were compared with rac-ethylenebis(indenyl)zirconium dichloride ( 1 ) activated with either MAO or the cation forming agent, triphenyl carbenium tetrakis(pentafluorophenyl)borate ( 2 ), with triethylalumium (TEA). The activities of the heterogeneous catalysts depend on the presence or absence of the Lewis base, were relatively insensitive to the temperature of polymerization, and produce poly(hexene) with molecular weights up to 10⁶. The 1 /MAO catalyst has about five times higher activity at 50°C but is almost inactive at ?30°C; the overall activation energy is 12.4 kcal mol^?1. In contrast, the activity for hexene polymerization by the 1/2 /TEA catalyst is actually slightly greater at lower temperature. The MW's of poly(hexene) obtained with the zirconocenium catalysts are only in the tens of thousands because of rapid β-hydride elimination by the electrophilic cationic Zr center. © 1993 John Wiley & Sons, Inc.     

Syndioselective propylene polymerization catalyzed by rac-2,2-dimethylpropylidene (1-η5-cyclopentadienyl) (1-η5-fluorenyl) dichlorozirconium

Syndioselective propylene polymerization has been promoted by rac-2,2-dimethylpropylidene (1-η⁵-cyclopentadienyl) (1-η⁵-fluorenyl) dichlorozirconium ( 1 ). The active catalytic species were generated using either triphenylcarbenium tetrakis (pentafluorophenyl) borate ( 2 ) (Zr⁺ method) or methylaluminoxane (MAO method). The former exhibited much higher activity than the latter, especially at low polymerization temperatures (T_p). Syndiotactic poly (propylene) (s-PP) obtained at T_p = ?20°C has T_m approaching 160°C, [rrrr] pentad fraction of 0.92 to 0.95, and 45% crystallinity (X_c). It crystallized in two antichiral unit cells B and C. The C structure is favored by low temperature of polymerization, slow crystallization from melt, and annealing. The s-PP has M?_w/M?_n ranging from 3.6 to 4.4, which can be separated into stereoregular fractions soluble in heptane and hexane and stereoirregular fractions soluble in pentane, ether, and acetone. Therefore, this system cannot be considered to be a single-site catalyst. A parallel study was made on the isopropylidene (1-η⁵-cyclopentadienyl) (1-η⁵-fluorenyl) dichlorozirconium ( 3 )/MAO catalyst. Molecular mechanics calculations were performed for all combinations of the configuration of asymmetric centers. The steric energy favors syndiotactic enchainment for both catalysts 1 and 3 , with 1 forming the more syndioselective catalyst. © 1994 John Wiley & Sons, Inc.     

Activation of hafnocene catalyzed polymerization of 1-hexene with MAO and borate

A study of 1-hexene polymerization with ethylene-bis(9-fluorenyl) hafnium dichloride has been carried out using two different cocatalyst systems, methyl-aluminoxane/trimethylaluminum (MAO/TMA) and tris-isobutyl-aluminum/N,N-dimethylanilinium tetrakis(pentafluorophenyl) borate (TIBA/borate). When MAO/TMA was used, 1-hexene polymerized into a low molar mass poly(1-hexene) with low catalytic activity. Activation with TIBA/borate increased polymerization activity drastically as well as the molar mass of the polymers. In order to analyze differences in the activity profiles, UV-Vis spectroscopy was employed to investigate ligand to metal charge transitions (LMCT) of the hafnocene dichloride during the activation process. The low catalytic activity and the fast chain transfer to the cocatalyst with MAO/TMA may originate from strong bonding between the metallocene cation and the MAO/TMA species thus obstructing monomer coordination and insertion.     

Nature of the active component in the catalytic system prepared from titanium(III) chloride(AA), ethylaluminum dichloride,and tetrakis(dimethylamino)silane,in the polymerization of propylene

The chemistry of the titanium(III) chloride(AA)–ethylaluminum dichloride–tetrakis-(dimethylamino)silane system for the polymerization of propylene was studied. A complex of ethylaluminum dichloride with tetrakis(dimethylamino)silane was isolated. It was shown that this complex contains ethylaluminum dichloride and tetrakis(dimethylamino)silane in the ratio of 2:1. This complex with titanium(III) chloride is responsible for the polymerization activity.     

Substituent effects on titanocenium catalysts

Titanocene dichloride (1) and its bis(trifluoromethyl) (2) and bis(N,N-dimethylamino) (3) derivatives have been compared as catalysts for ethylene and propylene polymerizations using both methylaluminoxane (MAO) and triphenylcarbenium tetrakis(pentafluorophenyl)borate (4)/triisobutylaluminum (TIBA) as cocatalysts. The differences between the activities of the three ‘free’ titanocenium ions and the M _w of the polyolefins produced by them may be attributable to the relative stabilities of the intermediate olefin–titanocenium π-complexes. Interaction of either the neutral MAO or its anion with the titanocenium species may be responsible for the significantly lower catalytic efficiencies when the precursors were activated by MAO than by the 4/TIBA system.     

Ethylene and propylene polymerization behavior of a series of bis(phenoxy–imine)titanium complexes

This contribution reports ethylene and propylene polymerization behavior of a series of Ti complexes bearing a pair of phenoxy–imine chelate ligands. The bis(phenoxy–imine)Ti complexes in conjunction with methylalumoxane (MAO) can be active catalysts for the polymerization of ethylene. Unexpectedly, this C₂ symmetric catalyst produces syndiotactic polypropylene. ¹³C NMR spectroscopy has revealed that the syndiotacticity arises from a chain-end control mechanism. Substitutions on the phenoxy–imine ligands have substantial effects on both ethylene and propylene polymerization behavior of the complexes. In particular, the steric bulk of the substituent ortho to the phenoxy–oxygen is fundamental to obtaining high activity and high molecular weight for ethylene polymerization and high syndioselectivity for the chain-end controlled propylene polymerization. The highest ethylene polymerization activity, 3240 kg/mol-cat h, exhibited by a complex having a t-butyl group ortho to the phenoxy–oxygen, represents one of the highest reported to date for Ti-based non-metallocene catalysts. Additionally, the polypropylene produced exhibits a T_m, 140 °C, and syndioselectivity, rrrr 83.7% (achieved by a complex bearing a trimethylsilyl group ortho to the phenoxy–oxygen) that are among the highest for polypropylenes produced via a chain-end control mechanism. Hence, the bis(phenoxy–imine)Ti complexes are rare examples of non-metallocene catalysts that are useful for the polymerization of not only ethylene but also propylene.     

合成高分子量无规聚丙烯的研究 Ⅰ.单茂基钛化合物/MAO催化丙烯聚合

用合成得到的五甲基环戊二烯基三苄氧基钛［ＣｐＴｉ（ＯＢｚ）３］与甲基铝氧烷（ＭＡＯ）组成新型催化体系进行丙烯的均聚合,研究了影响聚合活性及产物分子量的各种因素．结果表明,用甲基取代钛化合物茂环上的氢可使聚合产物分子量增大一个数量级,所制得的聚丙烯为无规聚丙烯,具有高分子量（Ｍｗ＝２０～１００×１０４）．     

Syntheses and models for stereospecific metallocenes

Stereospecific, bridged [LL']M(R)⁺ catalysts (L, L' = substituted-cp, ind, or flu; R = hydrocarbyl) have been prepared by three new synthetic procedures. Propylene polymerizations with our new catalyst synthetic reagents, tris(pentafluorophenyl)boron (F15), magnesium dichloride, and trityl tetrakis(pentafluorophenyl)borate (trityl-F20) are compared with results obtained with the N, N-dimethyl-anilinium-F20 salt and with methylaluminoxane (MAO). Trimethylaluminium (TMA) or triethylaluminium(TEAL) scavenged poisons in the MAO free polymerizations. The site-control mechanism is discussed.     

Novel Unsymmetric α‐Diimine Nickel(II) Complexes: Suitable Catalysts for Copolymerization Reactions

We established a strategy to synthesize novel unsymmetric 2,3‐diaza‐1,4‐dithiane ligands. Reaction of [Ni(acac)₂] and trityl tetrakis(pentafluorophenyl)borate in the presence of these ligands afforded the corresponding salt‐type complexes. All new compounds were characterized by means of elemental analysis and NMR spectroscopy, and the complexes additionally by mass spectroscopy. NMR spectroscopic experiments on polymers generated by the symmetric ligand/trimethylaluminum catalyst system showed that all products were nearly linear, independent of the polymerization conditions. By contrast, polymers produced by the unsymmetric ligand/trimethylaluminum catalyst system under homopolymerization conditions were branched (15–24 ‰). Additionally, copolymerization experiments with propylene and 1‐hexene afforded copolymers with a branching level of up to 50 ‰.     

茂－茚锆金属络合物催化乙烯/1－己烯共聚和丙稀均聚研究

Complexes （R^1Cp）（R^2Ind）ZrCl2, the catalysts previously reported active for ethylene polymerization showed high activity in ethylene/1-hexene copolymerization and propylene polymerization in the presence of MAO. The content of 1-hexene in copolymers ranged from 1.2% to 3.2%. In propylene polymerization the complex 1 showed the highest activity, up to 1.2×10^6 g of polypropylene per mol of catalyst per hour. Based on the analysis of NMR spectral data, the relationships between complex structures and polymerization results were explored.     

Propene polymerization with rac-Me2Si(2-Me-Benz[e]Ind)2ZrX2 [X = Cl,Me] using different cation-generating reagents

Propene was polymerized with methylaluminoxane (MAO) and cationic activated rac-dimethylsilylene-2-methylbenz[e]indenylzirconocene [ MBI-Cl ₂] and [ MBI-Me ₂]. For cationic activation of the MBI-Me ₂ system tris(pentafluorophenyl)borane [I], N,N-dimethylanilinium tetra(pentafluorophenyl)borate [III] were used. The MAO-activated dimethyl complex showed higher activity with respect to the dichloride system using high catalyst concentrations and [Al]/[Zr] ratios. Most effective cationic activator for MBI-Me ₂ was N,N-dimethylanilinium tetra(pentafluorophenyl)borate [II] in combination with Al(i-Bu₃). Using tris(pentafluorophenyl)borane [I] at different polymerization conditions or N,N-dimethylanilinium tetra(pentafluorophenyl)borate [II] in combination with Al(Et)₃ no propene polymerization was observed due to the occurrence of reduction of the catalytically active site.     

亚乙基桥联-(4-取代茚)(芴)锆金属络合物的合成及其催化α-烯烃聚合反应

首次合成了3个C1-对称亚乙基桥联型-(4-取代茚)(芴)锆络合物2a～2c.并以甲基铝氧烷(MAO)为助催化剂用于催化丙烯聚合反应,所得聚丙烯具有较高的等规立构规整度,且随聚合温度的降低而升高.0℃时茚环2-位有甲基取代的络合物2a表现出最高的等规选择性,为93.6%;而60℃时络合物2a～2c都表现出最高的催化活性...     

Metallocene‐mediated cationic ring‐opening polymerization of 2‐methyl‐ and 2‐phenyl‐oxazoline

The cationic ring‐opening polymerization of 2‐methyl‐2‐oxazoline and 2‐phenyl‐2‐oxazoline was efficiently used using bis(η⁵‐cyclopentadienyl)dimethyl zirconium, Cp₂ZrMe₂, or bis(η⁵‐tert‐butyl‐cyclopentadienyl)dimethyl hafnium in combination with either tris(pentafluorophenyl)borate or tetrakis(pentafluorophenyl)borate dimethylanilinum salt as initiation systems. The evolution of polymer yield, molecular weight, and molecular weight distribution with time was examined. In addition, the influence of the initiation system and the monomer on the control of the polymerization was studied. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 000: 000–000, 2011     

Group 4 octahedral benzamidinate complexes: syntheses,structures, and catalytic activities in the polymerization of propylene modulated by pressure

The synthesis and structural X-ray diffraction studies for some benzamidinate ligations and several group 4 benzamidinate complexes are presented. The use of the cis-octahedral C(2)-symmetry compounds was studied to shed light on the conceptual applicability of these complexes as potential catalysts for the stereoregular polymerization of propylene. We demonstrate that the stereoregular polymerization of propylene catalyzed by early-transition metal octahedral benzamidinate complexes, activated with either MAO or B(C(6)F(5))(3) as cocatalysts, can be modulated by pressure (from atactic to isotactic through elastomers). The different effects in the polymerization process such as the nature of solvent or cocatalyst, temperature, pressure, molar ratio catalyst:cocatalyst, and the relationship between the symmetry of the complex and the polymer microstructure have been investigated. When the complex [4-CH(3)-C(6)H(4)C(NTMS)(2)](2)ZrMe(2) (9) was activated with MAO, it was found to be a good catalyst for the polymerization of propylene, at atmospheric pressure, producing an oily polymer resembling an atactic polypropylene. Being activated with B(C(6)F(5))(3), complex 9 produces a highly isotactic (mmmm = 98%) product. Likewise, when the polymerization of propylene was performed with complex 9 and MAO at high pressure (liquid propylene), a highly stereoregular polymer was also obtained. Larger activities and stereoregularities were achieved by performing the reaction in CH(2)Cl(2) as compared to toluene. Contrary to complex 9, at atmospheric pressure the complex [4-CH(3)-C(6)H(4)C(NTMS)(2)](2)TiMe(2) (10) is not active either in CH(2)Cl(2) or in toluene. At high pressure, complex 10 produces elastomeric polypropylene. Activities of the isolobal complexes [C(6)H(4)C(NTMS)(2)](2)ZrMe(2) (11) and [C(6)H(4)C(NTMS)(2)](2)TiMe(2) (12) were found to be larger than those of complexes 9 and 10, respectively. Contrary to the structures of the elastomeric polypropylenes described in the literature, the obtained elastomers are characterized by frequent alternation of the isotactic domains with stereodefects. The stereoregular errors are formed by the intramolecular epimerization of the growing chain at the last inserted unit. The epimerization reaction was corroborated through the isomerization of alkenes.     

Ethylene polymerization and copolymerization with hexene-1 on supported metallocene catalysts based on (C<Subscript>5</Subscript>H<Subscript>5</Subscript>)<Subscript>4</Subscript>Zr and methylaluminoxane

New supported metallocene catalysts based on tetrakis(cyclopentadienyl)zirconium + methylaluminoxane (MAO) were prepared and tested for ethylene polymerization and copolymerization with hexene-1. It was shown that silica gel of the Davison 952 brand is the best support for such catalysts. The maximum catalyst activity was achieved on the support impregnated with the (C₅H₅)₄Zr-MAO complex. The addition of hexene-1 into the liquid phase resulted in acceleration of polymerization and an increase in the product yield. The morphological, rheological, and other properties of polymers and copolymers were studied. The test catalytic system can be used for manufacture of low-, medium-, and high-density polyethylenes with various stress-strain characteristics.     

Propylene polymerization with nickel–diimine complexes containing pseudohalides

DADNiX₂ nickel–diimine complexes [DAD = 2,6‐iPr₂? C₆H₃? N?C(Me)? C(Me)?N? 2,6‐iPr₂? C₆H₃] containing nonchelating pseudohalide ligands [X = isothiocyanate (NCS) for complex 1 and isoselenocyanate (NCSe) for complex 2 ] were synthesized, and the propylene polymerization with these complexes and also with the Br ligand (X = Br for complex 3 ) activated by methylaluminoxane (MAO) were investigated (systems 1 , 2 , and 3 /MAO). The polypropylenes obtained with systems 1 , 2 , and 3 were amorphous polymers and had high molecular weights and narrow molecular weight distributions. Catalyst system 1 showed a relatively high activity even at a low Al/Ni ratio and reached the maximum activity at the molar ratio of Al/Ni = 500, unlike system 3 . Increases in the reaction temperature and propylene pressure favored an increase in the catalytic activity. The spectra of polypropylenes looked like those of propylene–ethylene copolymers containing syndiotactic propylene and ethylene sequences. At the same temperature and pressure, system 2 presented the highest number of propylene sequences, and system 3 presented the lowest. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 458–466, 2006     

Multinuclear cobalt–salen complexes with phenylene linker for epoxide polymerizations

Di‐ and trinuclear cobalt (Co)–salen complexes with a benzene ring as a rigid linker were explored for epoxide polymerizations. The dinuclear Co–salen complex with a 1,2‐phenylene linker showed higher catalytic activity than the dinuclear Co–salen complex with a 1,3‐phenylene linker and the trinuclear Co–salen complex with a 1,3,5‐benzenetriyl linker for the copolymerization of propylene oxide (PO) with carbon dioxide. A combination of the absolute configuration of the two Co–salen moieties was found to affect its catalytic activity. The optimized dinuclear Co–salen complex with a heterochiral combination demonstrated highest activity and maintained its catalytic activity under a low catalyst concentration. The heterochiral dinuclear Co–salen complex also showed high activity for the copolymerization of PO with cyclic anhydride. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2150–2159     

Fluorinated bis(phenoxyketimine)titanium complexes for the living, isoselective polymerization of propylene: multiblock isotactic polypropylene copolymers via sequential monomer addition

A series of bis(phenoxyketimine)titanium dichloride complexes were synthesized and evaluated as catalysts for living, isoselective propylene polymerization upon activation with methylaluminoxane (MAO). Catalysts bearing phenoxyketimine ligands with different substituents at the ortho and para positions of the phenolate ring and substituents at the ketimine carbon were investigated. The identity of the ketimine substituent had the largest effect on the activity and isoselectivity of propylene polymerization. Complex 12/MAO promoted the living, isoselective polymerization of propylene ([m4] = 0.73, alpha = 0.94). This catalyst system was used for the synthesis of a number of block copolymers featuring isotactic polypropylene semicrystalline blocks and poly(ethylene-co-propylene) amorphous blocks. Several triblock samples with varying block lengths, a pentablock, and a heptablock copolymer were synthesized. Mechanical testing has revealed that each is elastomeric with elongations at break between approximately 790-1000%.     

Heavy-atom kinetic isotope effects,cocatalysts, and the propagation transition state for polymerization of 1-hexene using the rac-(C(2)H(4)(1-indenyl)(2))ZrMe(2) catalyst precursor

Using 13C NMR techniques, the 12C/13C kinetic isotope effects (KIEs) for the polymerization of 1-hexene catalyzed by rac-(C2H4(1-indenyl)2)ZrMe2 in the presence of four different cocatalysts (tris(pentfluorophenyl)borane, tris(pentafluorophenyl)alane, anilinium tetrakis(pentafluorophenyl)borate, and methylalumoxane) have been determined. All cocatalysts yield similar KIEs within experimental uncertainty, with values of 1.009(1) and 1.017(2) at C1 and C2, respectively. Ab initio DFT computational modeling of the polymerization KIE indicates that alkene binding to the catalyst must be reversible, with the majority of the KIE developing in the subsequent migratory insertion reaction.