Catalytic properties of the phenoxyimine zirconium complexes, viz., bis[N-(3,5-di-tert-butylsalicylidene)anilinato]zirconium(IV) dichloride (1) and its fluorinated analog, bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6-tetrafluoroanilinato]zirconium(IV) dichloride (2), were studied. Ethylene homopolymerization and copolymerization of ethylene with α-olefins were chosen as catalytic reactions,
and various organoaluminum compounds served as activators: commercial polymethylalumoxane (MAO) containing ∼35 mol.% of trimethylaluminum
(TMA), MAO purified from TMA (“dry” MAO), and “classical” organoaluminum compounds, namely, TMA and triisobutylaluminum (TIBA).
Complex 1 is not activated by “dry” MAO but is efficiently transformed into the catalytically active state by commercial MAO, “conventional”
TMA, and TIBA. These processes give low-molecular-weight polyethylenes (PE) characterized by high values of polydispersity
indices and by polymodal curves of gel permeation chromatography (GPC). The order of decreasing the efficiency of activation
for the cocatalysts is MAO > TIBA > TMA. Fluorinated complex 2 exhibits a high activity after its treatment with MAO and “dry” MAO, the activity is much lower upon mixing with TIBA, and
complex 2 is inactive when using TMA. In the copolymerization of ethylene with hex-1-ene and dec-1-ene, complex 1 treated with MAO is highly active but gives a low level of insertion of the comonomer (1–2 mol.% in the copolymer). Complex
2 activated with “dry” MAO is more efficient in the copolymerization of ethylene with propylene or hex-1-ene but, like complex
1, it does not produce copolymers with a high content of the comonomer. The both catalysts provide the insertion of α-olefin
as isolated units separated by extended sections of the chain consisting of ethylene units. 相似文献
The transformations of bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6-tetrafluoroanilinato]-titanium(iv) dichloride (L2TiCl2) occurring in toluene under the action of methylalumoxane (MAO) were studied by 1H NMR spectroscopy. The commercially available MAO containing trimethylaluminum (AlMe3) and MAO free of AlMe3 (the so called “dry” MAO) were used. The catalytic transformations of hex-1-ene involving the systems L2TiCl2-MAO were studied. We proposed the structures of the cationic titanium complexes formed in the absence and in the presence
of hex-1-ene under the action of MAO. In the absence of olefin, neutral and cationic titanium complexes are decomposed under
the action of AlMe3 according to the exchange reaction of the complex ligand with the methyl groups of AlMe3 to form LAlMe2. The neutral complexes react considerably faster than the cationic ones. In the presence of olefin, decomposition of complexes
under the action of AlMe3 is suppressed. The titanium complex activated by “dry” MAO isomerizes hex-1-ene to hex-2-ene. In the presence of large amounts
of TMA (commercial MAO), this reaction does not take place. 相似文献
A FI (phenoxy-imine) Zr-based catalyst of bis[1-[(2,6-diisopropylphenyl)imino]methyl-3,6-ditertbutyl-2-naphtholato]zirconium(IV) dichloride was prepared by changing the ligand from salicylaldehyde imine ligand which is used for well known FI catalysts to 2-hydroxynaphthalene-1-carbaldehyde imine ligand and used for polymerization of ethylene. Replacement of the phenoxy-group by naphtholato-group does not provide any spatial difficulties in the ortho-position to oxygen, but introduction of the bulky alkyl substitution groups at the ortho position of the naphthoxy-oxygen and on phenyl ring on the N dramatically enhanced the activity of the catalyst, as well as viscosity average molecular weight (Mv) of the obtained polymer. The prepared catalyst could produce a high molecular weight polyethylene under the polymerization conditions used. The optimum activity of the catalyst was obtained at the reaction temperature of 40°C. Activity of the catalyst was continuously increased with increasing MAO concentration and monomer pressure and no optimum activity was observed in the range studied. Crystallinity and melting point of the obtained polymer were between 55–65% and 125–135°C, respectively. A molecular weight distribution of 1.55–2.75 was obtained under the polymerization condition used and the polydispersity was broadened with the time. The activity of the catalyst was not sensitive to the hydrogen concentration. However, higher amount of hydrogen could slightly increase the activity of the catalyst. 相似文献
New fluorinated bis(phenoxy-imine)zirconium complexes bearing halogen substituents in the ortho and para positions of the phenolate rings, bis[N-(3,5-dibromosalycilidene)-2,3,4,5,6-pentafluoroaniline]-Zr(IV) dichloride (1) and bis[N-(3,5-dichlorosalycilidene)-2,3,4,5,6-pentafluoroaniline]-Zr(IV) dichloride (2) have been synthesized and used as precatalysts in the polymerization of propylene and 1-hexene. Their catalytic behaviour was compared with that of the analogous fluorinated zirconium complexes bearing alkyl groups in the same positions of the phenolate rings to investigate the effects produced by the introduction of additional electron-withdrawing halogen substituents. Complexes 1 and 2 produce stereoirregular, slightly syndiotactic enriched polypropylenes showing enhanced catalytic activities and an improved primary regioselectivity. Both catalysts promote efficiently the oligomerization of 1-hexene to atactic and regioregular oligomers. Interestingly for both the studied monomers it is possible to control the molecular weights and the structures of end groups of the produced polymeric chains by an appropriate choice of the cocatalyst. Functionalization reactions of the unsaturated polymeric chains selectively produced are also reported. 相似文献
Addition polymerization of norbornene was performed with several pyridine bis(imine) cobalt dichloride complexes activated with methylaluminoxane (MAO), first described for ethylene polymerization. For the first time, norbornene was also polymerized with CoCl2 associated to MAO. The influence of several reaction parameters has been investigated. Quite different behavior was observed compared with ethylene polymerization. Moreover, the copolymerization of ethylene and norbornene with these complexes was not possible but led to a mixture of both homopolymers.
The pyridine bis(imine) cobalt dichloride complexes used in this study. 相似文献
This contribution reports on the syntheses, structures and olefin polymerization behavior of Ti complexes having a pair of chelating pyrrolide-imine [N−,N] ligands. X-ray analyses as well as 1H NMR studies demonstrate that bis(pyrrolide-imine) Ti complexes (named PI Catalysts) contain approximately octahedrally coordinated metal centers with mutually trans-pyrrolide-Ns, cis-imine-Ns and cis-Cls. DFT studies suggest that PI Catalysts, when activated, provide a metal alkyl in the cis position to a vacant coordination site for monomer binding. These theoretical studies also show that the active species derived from PI Catalysts normally possess higher electrophilicity and a sterically more open nature compared with those produced using bis(phenoxy-imine) Ti complexes (Ti-FI Catalysts) which are known as high performance olefin polymerization catalysts. These structural as well as electronic features suggest that PI Catalysts have high potential for the polymerization of olefinic monomers.Unlike high performance Ti-FI Catalysts, PI Catalysts do not require the presence of steric bulk in close proximity to the anionic donor. PI Catalysts combined with MAO display high ethylene polymerization activities (max. 33,200 kg-polymer/mol-cat/h, 25 °C, atmospheric pressure) comparable to those obtained with early group 4 metallocene catalysts (e.g., Cp2TiCl2 16,700 kg-polymer/mol-cat/h) under identical conditions. As expected, PI Catalysts exhibit higher incorporation capability for propylene and 1-hexene relative to FI Catalysts though the incorporation levels are lower than those for Cp2TiCl2. To our surprise, PI Catalysts/MAO show remarkably high norbornene (NB) incorporation, superior to that seen with the [Me2Si(Me4Cp)N-tBu]TiCl2 (CGC) catalyst system, and they readily form ethylene-NB copolymers with high NB contents. The highly electrophilic and sterically open nature is probably responsible for the high NB affinity. Additionally, PI Catalysts/MAO possess characteristics of living ethylene polymerization (though under limited conditions) and afford high molecular weight PEs with very narrow molecular weight distributions (Mn 225,000, Mw/Mn 1.15, 10-s polymerization, 25 °C). Moreover, these catalysts can copolymerize ethylene and NB in a highly controlled living manner to afford monodisperse alternating copolymers with very high molecular weights (Mn > 500,000, Mw/Mn < 1.2) at room temperature. This unique living nature allows the preparation of a number of ethylene- and NB-based block copolymers, including PE-b-poly(ethylene-co-NB) and poly(ethylene-co-NB)a-b-poly(ethylene-co-NB)b, in which each segment contains a different NB content. These are probably the first examples of the syntheses of block copolymers from ethylene and NB. Consequently, the discovery and application of PI Catalysts has exercised a significant influence on olefin polymerization catalysis and polymer synthesis. 相似文献
Synthesis and structure of Ti complex having a pair of chelating aminotropone[O-N]ligand have been reported.Calculations of density functional theory(DFT) studies suggest that bis(aminotropone) Ti complex,when activated with methylaluminoxane (MAO),have high potential for the polymerization of olefinic monomers.These theoretical studies also show that the active species derived from bis(aminotropone) Ti catalyst normally possess higher electrophilicity nature compared with those produced using bis(phenoxyimine) Ti complexes(Ti-FI catalysts) which are known as high performance olefin polymerization catalysts. Bis(aminotropone) Ti catalyst generates a catalytically active species that has higher electrophilicity than a Ti-FI catalysts. 相似文献
Two macrocyclic dinuclear complexes, [Cu2L1](PF6)2 and [Cu2L2](ClO4)2, were synthesized by cyclo-condensation between N,N′-bis(3-formyl-5-methylsalicylidene)ethylenediimine or N,N′- bis(3-formyl-5-n-butylsalicylidene)ethylenediimine and ethylenediamine in the presence of Cu2+ ions. The crystal structures of the complexes were studied. The variable-temperature magnetic susceptibilities and cyclic
voltammograms of the complexes were measured. The magnetic and electrochemical properties of the complexes were discussed.
The results show that the complexes display very strong antiferromagnetic exchanges and that all copper(II) complexes undergo
a one-electron transfer process. 相似文献
Changes in the molecular-weight characteristics of the product of ethylene polymerization in the course of reaction in the
presence of a homogeneous catalytic system and in the number and reactivity of catalyst active sites were studied. The catalytic
system consisted of bis[N-(3-tert-butylsalicylidene)anilinato]zirconium dichloride and methylalumoxane as an activator. This catalytic system exhibited the
signs of unsteady-state conditions: the rate of polymerization dramatically decreased as the reaction time increased. At the
onset of polymerization (to 5 min), the catalyst was single-site, and it produced low-molecular-weight polyethylene with Mw = (4–10) × 103 g/mol. The fraction of active sites at the initial point in time was as high as 11% based on the initial amount of the zirconium
complex. The reactivity of these centers was very high (the rate constant of polymer chain growth was 5.4 × 104 l mol−1 s−1 at 35°C). As the polymerization time increased, the number of active sites decreased and the molecular-weight distribution
of polyethylene broadened because of the decay of a portion of initial centers and the formation of new centers that produced
high-molecular-weight polyethylene with Mw to 130 × 104 g/mol. The propagation rate constant measured at a sufficiently long polymerization time (20 min) was lower than that at
the initial point in time; this fact suggests the much lower reactivity of the new active sites. 相似文献
The preparation and spectroscopic and structural characterization of three ZnII complexes with bis[N‐(2,6‐dimethylphenyl)imine]acenaphthene, L1, and with bis[N‐(2‐ethylphenyl)imine]acenaphthene, L2, are decribed herein. Two of the complexes were prepared from ZnCl2 and the third from Zn(NCS)2. One‐pot reaction techniques were used, leading to high yields. The complexes were characterized by microanalysis, IR and 1H NMR spectroscopy, and single‐crystal X‐ray diffraction. The structures of the complexes are significantly different, with the chloride‐containing species forming distorted tetrahedra around the metal, whereas its thiocyanate analog is dimeric, with each metal at the center of a distorted square pyramid, with bridging and terminal [SCN]– ligands. 相似文献
Highly syndiotactic “living” poly(propylene)s were synthesized at 25°C using a bis[N‐(3‐tert‐butylsalicylidene)‐2,3,4,5,6‐pentafluoroanilinato]titanium (IV) dichloride/MAO catalyst system, and microstructures of the polymer were analyzed by means of 13C NMR spectroscopy. The syndiotactic poly(propylene) contains isobutyl, isopentyl and propyl end groups, suggesting that the living polymerization of propylene was initiated via 1,2‐insertion, followed by 2,1‐insertion as the principal mode of polymerization. Pentad distribution analysis revealed that the syndiospecific polymerization proceeds under chain‐end control. 相似文献
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 Mw 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. 相似文献
The [VO(acac)2]/Schiff base [R-2-(N-3,5-di-tert-butylsalicylidene)amino-2-phenyl-1-ethanol, S-2-(N-3,5-di-tert-butylsalicylidene)amino-3,3-dimethyl-1-butanol, S-2-(N-3,5-di-tert-butylsalicylidene)amino-3-methyl-1-butanol, or R-2-(N-3,5-di-tert-butylsalicylidene)amino-3-phenyl-1-propanol]/H2O2 catalytic systems for the asymmetric oxidation of sulfides and the [VO(acac)2]/(3bR,4aR)-2-(3,4,4-trimethyl-3b,4,4a,5-tetrahydrocyclopropa[3,4]cyclopenta[1,2-c]pyrazol-1-yl)ethanol/tert-butyl hydroperoxide/TBHP and VO(OAlkyl)3/[2,2]paracyclophane-4-carboxylic acid N-(1,1-dimethylethyl)-N-hydroxamide/TBHP catalytic systems for the asymmetric epoxidation of allylic alcohols were studied using 13C, 51V, and 17O NMR spectroscopy. The key intermediates of these systems (peroxo and alkylperoxo complexes of vanadium(V)) were detected, their structures in solution were studied, and the reactivity was evaluated. 相似文献
This contribution reports Mitsui's R&D activities in the field of catalysis technology focusing on molecular catalysts. Examples of the high-performance molecular catalysts developed at Mitsui include bis(phenoxy-imine) group 4 transition metal complex catalysts (FI Catalysts), phosphazene catalysts (PZN catalysts) and b(beta)-ketoiminato Co(II) complex catalysts. Many of the materials stemming from these catalysts were either difficult or impossible to prepare using conventional catalysts. 相似文献
Based on new results as well as the reported data, the ethylene and propylene polymerization behavior of bis(phenoxy-imine) Ti complexes (Ti-FI Catalysts) combined with MAO (particularly that of their fluorinated versions) is discussed, with an emphasis on the characteristics and mechanisms of living ethylene and syndioselective living propylene polymerization. Unlike common living olefin polymerization catalysts, fluorinated Ti-FI Catalysts with MAO display thermally robust living behavior and polymerize ethylene in a highly controlled manner at temperatures as high as 50 °C. Additionally, despite being C2-symmetric catalysts, fluorinated Ti-FI Catalysts/MAO mediate highly syndioselective living propylene polymerization. Fluorinated Ti-FI Catalysts that we developed are the first examples of catalysts that induce the living polymerization of both ethylene and propylene. In addition, they are also the first examples of living and, at the same time, highly stereoselective propylene polymerization catalysts. The versatile and robust living nature of the fluorinated Ti-FI Catalysts allows the preparation of a wide variety of unique living polymers; some of which can even be produced catalytically. On the basis of theoretical calculations as well as experimental results, we conclude that these unusual polymerization features of fluorinated Ti-FI Catalysts originate from an attractive interaction between the ligand and a growing polymer chain and/or the fluxional character of the catalyst coupled with 2,1-regiochemistry. This is in stark contrast to group 4 metallocene catalysts, which control olefin polymerization mainly by repulsive interactions based on the rigidly organized ligand frameworks. 相似文献