共查询到20条相似文献,搜索用时 31 毫秒
1.
A. A. Barabanov N. V. Semikolenova G. D. Bukatov M. A. Mats’ko V. A. Zakharov 《Polymer Science Series B》2008,50(11-12):326-329
The number of active centers C p and propagation rate constant k p upon ethylene polymerization with a homogeneous catalyst based on a cobalt complex with bis[imino]pyridyl ligands (LCoCl2, where L is 2,6-(2,6-(Me)2C6H3N=CMe)2C5H3N) using methylaluminoxane as an activator was determined by quenching by radioactive carbon monoxide (14CO). It was found that the drop in activity during polymerization on the above catalyst is due to the decreasing number of active centers (from 0.23 to 0.14 mol/mol Co within 15 min of polymerization); the propagation rate constant remained unchanged, 3.5 × 103 l/(mol s) at 35°C, which is substantially lower than for a catalyst based on an iron complex with analogous bis[imino]pyridyl ligands. It follows from the data on molecular mass characteristics of the produced polymer that the homogeneous catalyst LCoCl2/methylaluminoxane is of monocenter type, and the obtained value of the propagation rate constant reflects the true reactivity of its active centers. 相似文献
2.
合成了一系列α-二亚胺钴配合物[ArN=C(Me)-(Me)C=NAr]CoCl2(Ar=C6H5, 3a; 4-MeC6H4, 3b; 4-MeOC6H4, 3c; 4-FC6H4, 3d; 4-ClC6H4, 3e; 2-MeC6H4, 3f; 2-EtC6H4, 3g; 2-iPrC6H4, 3h; 2,4,6-Me3C6H2, 3i; 2,6-Et2C6H3, 3j; 2,6-iPrC6H3, 3k)和作为对比的吡啶双亚胺二氯化钴配合物(4a), 并用X射线单晶衍射方法研究了配合物3i, 3k和4a的分子结构. α-二亚胺钴配合物在倍半乙基氯化铝的作用下对丁二烯聚合有较高的催化活性,得到的顺式-1,4结构含量达98%,且有较高分子量(Mn≈1×104-1×105)的聚丁二烯. 配体的电子效应影响催化剂的活性及顺式-1,4选择性, 而配体的空间位阻对丁二烯聚合几乎没有影响. 详细研究了聚合时间、聚合温度、烷基铝助催化剂及铝比等条件对丁二烯聚合行为的影响. 相似文献
3.
Several phenoxy-imine ligands bearing o-trityl group in phenoxy moiety RN=CHArOH (Ar = C6H2(CPh3)tBu, R = 2,6-Me2C6H3 ( L 1 H ); 2,6-iPr2C6H3 ( L 2 H ); 3,5-(CF3)2C6H3 ( L 3 H ); 3,5-(OMe)2C6H3 ( L 4 H ); CHPh2 ( L 5 H ); CPh3 ( L 6 H )) were synthesized and characterized by1H NMR and 13C NMR spectroscopy. The vanadium complexes based on these ligands LVCl2(THF)2 ( 1–6 ) were synthesized via conventional transmetalation reaction in moderate to high yields. Complexes 1–6 were fully characterized by FT-IR, elemental analyses and the molecular structures of 1 , 2 ·H2O, (2 ·H2O ) 2 (μ-Cl) 2 , 4 , and 5 were confirmed by X-ray crystallographic analysis in which the six-coordinated vanadium centers are in a typical octahedral geometry. Upon activation with Et2AlCl in toluene, complexes 1–6 showed high activities in ethylene polymerization affording polymers with moderate molecular weight (5.9–11.8 × 104 Da). Moreover, in hexane or CH2Cl2, 1–6 /Et2AlCl exhibited enhanced activities. When activated with MAO or MMAO in toluene, these complexes showed relatively low activities but afforded polymers with ultra-high molecular weight (up to 3.30 × 106 Da). 1–6 /Et2AlCl also showed high activities in ethylene/1-hexene copolymerization at room temperature giving moderate molecular-weight polymers (6.5–11.4 × 104 Da) with co-monomer incorporation being of 6.0 ~ 7.8%. 相似文献
4.
Minoru Matsuda Yasuhiro Ishioroshi Kiichiro Seki 《Journal of polymer science. Part A, Polymer chemistry》1976,14(6):1337-1345
A kinetic study has been made of polymerization of methyl methacrylate initiated by an electron donor–acceptor complex of liquid SO2 (electron acceptor) and nicotine (donor) in the presence of carbon tetrachloride. It is concluded that the polymerization proceeds through free-radical intermediates similar to the cases of liquid SO2–pyridine and liquid SO2–poly(2-vinylpyridine) complexes. The overall rate of polymerization is proportional to the square root of both liquid SO2 and nicotine concentrations, and the values of kp/kt½ under various polymerization conditions are in satisfactory agreement with the literature values. For the activation energy of initiation, 13.6 kcal/mole is estimated from the kp/kt½ values obtained at temperatures ranging from 0 to 80°C. 相似文献
5.
Yi Yan Shi-Fang Yuan Ming Liu Gregory A.Solan Yan-Ping Ma Tong-Ling Liang Wen-Hua Sun 《高分子科学》2022,40(3):266-279
A group of five bis(arylimino)pyridine-cobalt(Ⅱ)chloride complexes,[2-{(2,6-(Ph2CH)2-4-MeOC6H2)N=CMe}-6-(ArN=CMe)C_5 H3N]CoCl2(Ar=2,6-Me2C6H3Co1,2,6-Et2C6H3Co2,2,6-iPr2C6H3Co3,2,4,6-Me3C6H2Co4,2,6-Et2-4-MeC6H2Co5),each containing one N-4-methoxy-2,6-dibenzhydrylphenyl group and one smaller sterically/electronically variable N-aryl group,have been synthesized in good yield(>71%)from the corresponding neutral terdentate nitrogen-donor precursor,L1-L5.All complexes have been characterized by1H-NMR and FTIR spectroscopy with the former highlighting the paramagnetic nature of these cobaltous species and the unsymmetrical nature of the chelating ligand.The molecular structures of Co3 and Co4 emphasize the steric differences of the two inequivalent N-aryl groups and the distorted square pyramidal geometry about the metal centers.In the presence of MAO or MMAO,Co1-Co5 collectively displayed high activities for ethylene polymerization producing high molecular weight polyethylenes that,in general,exhibited narrow dispersities(M_w/M_n values:2.12-4.07).Notably,the least sterically hindered Co1 when activated with MAO was the most productive(6.92×106gPE·mol-1(Co)·h-1)at an operating temperature of60℃.Conversely,the most sterically hindered Co3/MMAO produced the highest molecular weight polyethylene(M_w=6.29×105g·mol-1).All the polymers displayed high linearity as demonstrated by their melting temperatures(>130℃)and their~1 H-and13C-NMR spectra.By comparison of Co1 with its para-methyl,-chloro and-nitro counterparts,the presence of the para-methoxy substituent showed the most noticeable effect of enhancing the thermal stability of the catalyst. 相似文献
6.
Nallasamy Palanisami 《Journal of organometallic chemistry》2006,691(15):3260-3266
Aminosilanes bearing bulky substituents on nitrogen centers, [(ArNH)2SiPhMe] (Ar = 2,6-iPr2C6H3 (1), 2,4,6-Me3C6H2 (2)) and half-sandwich lithium silylamide [(2,6-Et2C6H3NLi)(2,6-Et2C6H3NH)SiPh2] (3) have been prepared and characterized by elemental analysis, IR, EI mass and NMR (1H and 29Si) spectroscopic studies. The solid state structures of 2 and 3 have been determined by single crystal X-ray diffraction studies. The molecule 2 has a C1 symmetry due to the steric crowding, and the two N-H protons are approximately trans to each other. The amido nitrogen atoms in 2 show significant deviation from trigonal-planar geometry, and as a result, the observed Si-N bonds are marginally longer than those observed in aminosilanes with planar nitrogen atoms. The molecule 3 exists as discrete dimer with an inversion center. The Li ion in 3 forms intramolecular π-complex with the neighboring aryl (2,6-Et2C6H3) group, to form a half-sandwich lithium silylamide. 相似文献
7.
Vilve Nummert Mare Piirsalu Ilmar A. Koppel 《Central European Journal of Chemistry》2013,11(12):1964-1975
The second-order rate constants k for the alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2C6H5, in aqueous 50.9% acetonitrile have been measured spectrophotometrically at 25°C. The log k values for meta and para derivatives correlated well with the Hammett σm,p substituent constants. The log k values for ortho-substituted phenyl benzoates showed good correlations with the Charton equation, containing the inductive, σI, resonance, σ○ R, and steric, E s B, and Charton υ substituent constants. For ortho derivatives the predicted (log k X)calc values were calculated with equation (log k ortho)calc = (log k H AN)exp + 0.059 + 2.19σI + 0.304σ○ R + 2.79E s B ? 0.0164ΔEσI — 0.0854ΔEσ○ R, where DE is the solvent electrophilicity, ΔE = E AN — E H20 = ?5.84 for aqueous 50.9% acetonitrile. The predicted (log k X)calc values for phenyl ortho-, meta- and para-substituted benzoates in aqueous 50.9% acetonitrile at 25°C precisely coincided with the experimental log k values determined in the present work. The substituent effects from the benzoyl moiety and aryl moiety were compared by correlating the log k values for the alkaline hydrolysis of phenyl esters of substituted benzoic acids, X-C6H4CO2C6H5, in various media with the corresponding log k values for substituted phenyl benzoates, C6H5CO2C6H4-X. 相似文献
8.
The reaction of formation of guanidines by coupling of carbodiimides and aromatic amines using imido vanadium complexes as catalyst have been investigated. Results demonstrate that the complex V(N-2,6-iPr2C6H3)Cl3 is an effective catalyst for this process. 相似文献
9.
Zengfang Huang Keming Song Fengshou Liu Jieming Long Hao Hu Haiyang Gao Qing Wu 《Journal of polymer science. Part A, Polymer chemistry》2008,46(5):1618-1628
A series of 2‐aminopyridine Ni(II) complexes bearing different substituent groups {(2‐PyCH2NAr)NiBr, Ar = 2,4,6‐trimethylphenyl ( 3a) , 2,6‐dichlorophenyl ( 3b ), 2,6‐dimethylphenyl ( 3c) , 2,6‐diisopropylphenyl ( 3d ), 2,6‐difluorophenyl ( 3e ); (2‐PyCH2NHAr)2NiBr2, Ar = 2,6‐diisopropylphenyl ( 4a )} have been synthesized and investigated as precatalysts for ethylene polymerization in the presence of methylaluminoxane (MAO). High molecular weight branched polymers as well as short‐chain oligomers were simultaneously produced with these complexes. Enhancing the steric bulk of the ortho‐aryl‐substituents of the catalyst resulted in higher ratio of solid polymer to oligomer and higher molecular weight of the polymer. With ortho‐haloid‐substitution, the catalysts afforded a product with low polymer/oligomer ratio ( 3b ) and even only oligomers ( 3e ) in which C14H28 had the maximum content. Compared with complex 3d containing ionic ligand, complex 4a containing neutral ligand exhibited obviously low catalytic activity for ethylene polymerization. The molecular weight, molecular weight distribution, and microstructure of the resulted polymer were characterized by gel permeation chromatography and 13C NMR spectrogram. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1618–1628, 2008 相似文献
10.
(Imido)vanadium Complexes as Efficient Catalyst Precursors for Olefin Polymerization/Oligomerization
(Arylimido)vanadium(V) complexes containing anionic ancillary donor ligands of type, V(NAr)Cl2(L) (Ar = 2,6-Me2C6H3, L = aryloxo, ketimide phenoxyimine, etc.) exhibited high catalytic activities for ethylene polymerization in the presence
of Al cocatalyst; V(NAr)Cl2(O-2,6-Me2C6H3) showed the exceptionally high activities in the presence of halogenated Al alkyls such as Et2AlCl, EtAlCl2, etc. (Arylimido)vanadium(V)-alkylidene complexes, V(CHSiMe3)(NAr)(L′) (L′ = N=C
t
Bu2, O-2,6-
i
Pr2C6H3) exhibited the remarkable catalytic activities for ring-opening metathesis polymerization of norbornene. (Imido)vanadium(V)
complexes containing the (2-anilidomethyl)pyridine ligand, V(NR)Cl2[2-Ar′NCH2(C5H4N)] (R = 1-adamantyl, cyclohexyl, phenyl, Ar′ = 2,6-Me2C6H3, 2,6-
i
Pr2C6H3), exhibit the remarkable activities for ethylene dimerization in the presence of MAO, affording 1-butene exclusively (selectivity
90.4 to >99%). The steric bulk of the imido ligand plays an important role in the selectivity, and the electronic nature directly
affects the activity. 相似文献
11.
Qiumiao Shen Dr. Xiaoli Ma Dr. Wenling Li Wenqing Liu Yi Ding Prof. Zhi Yang Prof. Herbert W. Roesky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(51):11918-11923
The effective catalytic activity of organoaluminum compounds for the monohydroboration of carbodiimides has been demonstrated. Two aluminum complexes, 2 and 3 , were synthesized and characterized. The efficient catalytic performances of four aluminum hydride complexes L1AlH2 (L1=HC(CMeNAr)2, Ar=2,6-Et2C6H3; 1 ), L2AlH2(NMe3) (L2=o-C6H4F(CH=N-Ar), Ar=2,6-Et2C6H3; 2 ), L3AlH (L3=2,6-bis(1-methylethyl)-N-(2-pyridinylmethylene)phenylamine; 3 ), and L4AlH(NMe3) (L4=o-C6H4(N-Dipp)(CH=N-Dipp), Dipp=2,6-iPr2C6H3; 4 ), and an aluminum alkyl complex L1AlMe2 ( 5 ) were used for the monohydroboration of carbodiimides investigated under solvent-free and mild conditions. Compounds 1 – 3 and 5 can produce monohydroborated N-borylformamidine, whereas 4 can afford the C-borylformamidine product. A suggested mechanism of this reaction was explored, and the aluminum formamidinate compound 6 was characterized by single-crystal X-ray, also a stoichiometric reaction was investigated. 相似文献
12.
Artem A. Barabanov Gennady D. Bukatov Vladimir A. Zakharov 《Journal of polymer science. Part A, Polymer chemistry》2008,46(19):6621-6629
The inhibition of ethylene polymerization with radioactive carbon monoxide (14CO) was used to obtain data on the number of active sites (CP) and propagation rate constant (kP) at ethylene polymerization in the temperature range of 35–70 °C over supported catalysts LFeCl2/Al2O3, LFeCl2/SiO2, and LFeCl2/MgCl2 (L: 2,6‐(2,6‐(Me)2C6H3N = CMe)2C5H3N) with activator Al(i‐Bu)3. The values of effective activation energy (Eeff), activation energy of propagation reaction (EP), and temperature coefficients of variation of the number of active sites (ECp = Eeff ? EP) were determined. The activation energies of propagation reaction for catalysts LFeCl2/Al2O3, LFeCl2/SiO2, and LFeCl2/MgCl2 were found to be quite similar (5.2–5.7 kcal/mol). The number of active sites diminished considerably as the polymerization temperature decreased, the ECp value being 5.2–6.2 kcal/mol for these catalysts at polymerization in the presence of hydrogen. The reactions of reversible transformations of active centers to the surface hydride species at polymerization in the presence and absence of hydrogen are proposed as the derivation of ECp. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6621–6629, 2008 相似文献
13.
《Journal of Molecular Catalysis #》1979,5(1):1-13
In the catalytic systems Co(acac)2 or Co(acac)3, C3H4, (iBu)3Al, the active catalyst is formed via exchange of acac for iBu groups. From kinetic measurements it follows that Co(acac)2 and Co(acac)3 give the same catalyst with a polymerization rate constant k p = 29 ± 3 min−1 at relatively high Al/Co ratios (≥30). At low Al/Co ratios (≤0.05) a less active catalyst is formed with a polymerization rate constant kp = 3.6 ± 0.4 min−1, possibly due to the acac groups remaining in the catalytically active complex. The kinetic results show that the highly active cobalt catalyst is formed via an equilibrium with (iBu)3Al which indicates that the active catalyst complex is bimetallic. 相似文献
14.
The active center concentration C_p, the rate constant k_p, and the activation energy of chain propagation E_p in the polymerization of propylene with complex-type TiCl_3-(C_2H_5)_2AlCl catalyst system were studied. The Mn was corrected by (?) value determined by GPC. The values thus obtained for C_p, k_p, and E_p at 50℃were 3.01 mol/mol Ti, 6.27 1/mol·sec, and 5.10 Kcal/mol respectively.The kinetic parameters were compared with those obtained from conventional TiCl_3·AlCl_2 catalyst, showing that the higher activity of the complex-type catalyst over the conventional catalyst is not only due to the higher C_p of the former, but to a greater extent due to the increase of the k_p value. 相似文献
15.
Olayinka A. Oyetunji Banyaladzi D. Paphane Clifford A. L. Becker 《Transition Metal Chemistry》2006,31(7):951-957
The interaction of pyridine with four tetrakis(arylisocyanide)cobalt(II) complexes, [Co(CNR)4(ClO4)2] R = 2,6-Me2C6H3 (A), 2,4,6-Me3C6H2 (B), 2,6-Et2C6H3 (C) and 2,6-iPr2C6H3 (D), have been studied in 2,2,2-trifluoroethanol medium. The kinetics of the reactions were investigated over the 293–318 K
temperature range. The reaction profile exhibited two distinct processes, proposed to be an initial fast substitution followed
by a slow reduction, for each of the reactions. The pseudo first-order rate constants for both processes increased with increasing
concentration of pyridine with the reduction processes exhibiting saturation kinetics at high pyridine concentrations. Steric
hindrance plays a significant role in the rates of the reactions, as the rates decrease in the order k(A) > k(B) > k(C) > k(D). The activation enthalpies, ΔH‡, increase from A to D while the activation entropies, ΔS‡, are relatively similar for the four reactions, indicating similar transition states and hence similar mechanisms. Complex
B was first synthesized and characterized in this study. 相似文献
16.
Badral Gansukh Qiuyue Zhang Zygmunt Flisak Tongling Liang Yanping Ma Wen-Hua Sun 《应用有机金属化学》2020,34(4):e5471
The five unsymmetrical 2-[1-(2,4-dibenzhydryl-6-chlorophenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridine compounds (aryl: 2,6-Me2Ph L1 , 2,6-Et2Ph L2 , 2,6-iPr2Ph L3 , 2,4,6-Me3Ph L4 and 2,6-Et2–4-MePh L5 ) were prepared and characterized with FT-IR and 1H/13C NMR spectroscopy as well as elemental analysis. The treatment of L1 – L5 with CrCl3·3THF affords the corresponding chromium chloride complexes ( Cr1 – Cr5 ) in excellent yields. The molecular structures of Cr2 and Cr3 characterized by X-ray diffraction show a distorted octahedral geometry with three nitrogen atoms and three chlorine atoms around the metal center. On activation with either MAO or MMAO, Cr1 – Cr5 collectively display high activity (up to 14.96 × 106 g (PE) mol−1 (Cr) h−1 at 60 °C) affording highly linear polyethylene with low molecular weight distribution (Mw/Mn) ranging from 1.06 to 2.81. An in-depth catalytic evaluation of Cr1 was conducted in order to investigate how the cocatalyst type and its amount, reaction temperature and polymerization time affect the catalytic activities and polymer properties. 相似文献
17.
Yukio Imanishi Kotohiro Nomura 《Journal of polymer science. Part A, Polymer chemistry》2000,38(Z1):4613-4626
Olefin polymerizations catalyzed by Cp′TiCl2(O‐2,6‐iPr2C6H3) ( 1 – 5 ; Cp′ = cyclopentadienyl group), RuCl2(ethylene)(pybox) { 7 ; pybox = 2,6‐bis[(4S)‐4‐isopropyl‐2‐oxazolin‐2‐yl]pyridine}, and FeCl2(pybox) ( 8 ) were investigated in the presence of a cocatalyst. The Cp*TiCl2(O‐2,6‐iPr2C6H3) ( 5 )–methylaluminoxane (MAO) catalyst exhibited remarkable catalytic activity for both ethylene and 1‐hexene polymerizations, and the effect of the substituents on the cyclopentadienyl group was an important factor for the catalytic activity. A high level of 1‐hexene incorporation and a lower rE · rH value with 5 than with [Me2Si(C5Me4)(NtBu)]TiCl2 ( 6 ) were obtained, despite the rather wide bond angle of Cp Ti O (120.5°) of 5 compared with the bond angle of Cp Ti N of 6 (107.6°). The 7 –MAO catalyst exhibited moderate catalytic activity for ethylene homopolymerization and ethylene/1‐hexene copolymerization, and the resultant copolymer incorporated 1‐hexene. The 8 –MAO catalyst also exhibited activity for ethylene polymerization, and an attempted ethylene/1‐hexene copolymerization gave linear polyethylene. The efficient polymerization of a norbornene macromonomer bearing a ring‐opened poly(norbornene) substituent was accomplished by ringopening metathesis polymerization with the well‐defined Mo(CHCMe2Ph)(N‐2,6‐iPr2C6H3)[OCMe(CF3)2]2 ( 10 ). The key step for the macromonomer synthesis was the exclusive end‐capping of the ring‐opened poly(norbornene) with p‐Me3SiOC6H4CHO, and the use of 10 was effective for this polymerization proceeding with complete conversion. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4613–4626, 2000 相似文献
18.
Various (adamantylimido)vanadium(V) dialkyl complexes containing aryloxo ligands, V(NAd)(CH2SiMe3)2(OAr) [Ad = 1-adamantyl (1); Ar = Ph (a), 4-FC6H4 (b), 2,6-F2C6H3 (c), 2,6-Me2C6H3 (d), C6F5 (e)], have been prepared and identified. These complexes were employed as the catalyst precursors for ring-opening metathesis polymerization (ROMP) of norbornene (NBE) in the presence of PMe3 at 80 °C. The activity was strongly affected by the aryloxo substituent and increased in the order: C6H5 < 4-FC6H4 < 2,6-Me2C6H3 << 2,6-F2C6H3, C6F5. The same trend was observed in the ROMPs by the arylimido-aryloxo analogues, V(NAr′)(CH2SiMe3)2(OAr) (2a-e; Ar′ = 2,6-Me2C6H3), under the same conditions, and the activities by the arylimido analogues were generally higher than the adamantylimido analogues in most case. The (imido)vanadium(V) complexes containing O-2,6-F2C6H3 (1,2c) or OC6F5 (1,2e) exhibited high catalytic activities, and these results strongly suggest that electronic as well as steric factors play a role. Living ring-opening polymerization of THF proceeded in the presence of V(NAd) (CH2SiMe3)(OAr)2 (Ar = 2,6-Me2C6H3, C6F5) and [Ph3C][B(C6F5)4], affording high molecular weight polymers with narrow molecular weight distributions (ex. Mn = 2.11 × 105, Mw/Mn = 1.18). 相似文献
19.
Badral Gansukh Qiuyue Zhang Chantsalnyam Bariashir Arumugam Vignesh Yanping Ma Tongling Liang Wen-Hua Sun 《Molecules (Basel, Switzerland)》2020,25(23)
By dealing CrCl3∙3THF with the corresponding ligands (L1–L5), an array of fluoro-substituted chromium (III) chlorides (Cr1–Cr5) bearing 2-[1-(2,4-dibenzhydryl-6-fluoro- phenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridine (aryl = 2,6-Me2Ph Cr1, 2,6-Et2Ph Cr2, 2,6-iPr2Ph Cr3, 2,4,6-Me3Ph Cr4, 2,6-Et2-4-MePh Cr5) was synthesized in good yield and validated via Fourier Transform Infrared (FT-IR) spectroscopy and elemental analysis. Besides the routine characterizations, the single-crystal X-ray diffraction study revealed the solid-state structures of complexes Cr2 and Cr4 as the distorted-octahedral geometry around the chromium center. Activated by either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the chromium catalysts exhibited high activities toward ethylene polymerization with the MMAO-promoted polymerizations far more productive than with MAO (20.14 × 106 g (PE) mol−1 (Cr) h−1 vs. 10.03 × 106 g (PE) mol−1 (Cr) h−1). In both cases, the resultant polyethylenes were found as highly linear polyethylene waxes with low molecular weights around 1–2 kg mol−1 and narrow molecular weight distribution (MWD range: 1.68–2.25). In general, both the catalytic performance of the ortho-fluorinated chromium complexes and polymer properties have been the subject of a detailed investigation and proved to be highly dependent on the polymerization reaction parameters (including cocatalyst type and amount, reaction temperature, ethylene pressure and run time). 相似文献
20.
The copolymerizations of ethylene with 10-undecen-1-ol have been investigated using vanadium precatalysts, bis(imino)pyrrolyl vanadium(Ⅲ) complexes 1-3, 2,5-C4H2N(CH=NR)2VCl2(THF)2 [R = C6H5 (1), 2,6-iPr2C6H3 (2), C6F5 (3)], and the iminopyrrolyl and b-diketiminate ones for comparison. The polar monomer was pretreated by diethylaluminium chloride (present also as the cocatalyst) before the copolymerization. The monomer reactivity ratios were evaluated using the Fineman-Ross method. The ligand structure considerably influenced the catalytic activity and tolerance towards the polar monomer, the polar monomer incorporation and the molecular weights of the resultant copolymers. The bis(imino)pyrrolyl vanadium complexes exhibited promising catalytic performance for the copolymerization, and a high catalytic activity up to 3.84 kg/mmolv·h with a high comonomer incorporation of 14.0 mol% was achieved by complex 3 under mild conditions. 相似文献