Binuclear complexes have attracted extensive attention in fields such as catalysis because of their likely bimetallic synergistic effect;however,the mechanism and factors influencing this synergism remain unclear.In t...Binuclear complexes have attracted extensive attention in fields such as catalysis because of their likely bimetallic synergistic effect;however,the mechanism and factors influencing this synergism remain unclear.In this work,six bis-β-ketoimine binuclear titanium complexes4a-4f containing different alkylthio sidearms and configurations were synthesized and characterized by nuclear magnetic resonance hydrogen spectrum(~1H-NMR),nuclear magnetic resonance carbon spectrum(^(13)C-NMR),Fourier transform infrared spectrum(FTIR),and elemental analysis.The intermetallic distances of isomeric complexes 4a,4d,4e and 4f determined through density functional theory(DFT)optimization were in the order 4a<4d<4e<4f and were found to significantly influence the catalytic performance for ethylene(co)polymerization.These complexes could efficiently catalyze ethylene polymerization and ethylene/1-hexene or ethylene/1-octene copolymerization with high activity to produce highmolecular-weight ethylene homo-and co-polymers.Among the three binuclear titanium complexes 4a-4c with similar structures but different lengths of alkylthio sidearms,complex 4a,which contained the shortest methylthio sidearm,exhibited the highest activity for ethylene polymerization and copolymerization with 1-hexene or 1-octene.Additionally,for ethylene/1-hexene or ethylene/1-octene copolymerization,it showed the highest comonomer incorporation compared with propylthio(4b)and octylthio(4c)derivatives because of the smaller steric hindrance of the methyl group in 4a and the more open coordination space for vinyl monomers.Furthermore,among the isomeric complexes 4a,4d,4e and4f,complex 4a with the shortest bimetallic distance also exhibited the highest activity towards ethylene(co)polymerization,and the highest 1-hexene or 1-octene incorporation in comparison with its regioisomeric counterparts 4d,4e and p-phenyl-bridged analog 4f,owing to a more appropriate bimetallic distance that is conducive to a synergistic effect.展开更多
A series of“half-sandwich”bis(imino)pyridyl iron complexes with a substituted 8-(p-Xphenyl)naphthylamine(X=OMe,Me,CF3)was designed and synthesized by combining weakπ-πinteraction with steric and electronic tunings...A series of“half-sandwich”bis(imino)pyridyl iron complexes with a substituted 8-(p-Xphenyl)naphthylamine(X=OMe,Me,CF3)was designed and synthesized by combining weakπ-πinteraction with steric and electronic tunings.The weak noncovalentπ-πinteraction as well as the steric and electronic effects of bis(imino)pyridyl iron complexes were identified by experimental analyses and calculations.The roles of weakπ-πinteraction,steric bulk,and electronic tuning on the ethylene polymerization performance of bis(imino)pyridyl iron catalysts were studied in detail.The combination ofπ-πinteraction with steric and electronic tunings can access to thermally stable bis(imino)pyridyl iron at 130°C.展开更多
A series of phosphine-sulfonate ligands bearing 2-,3-and 4-vinylphenyl on the phosphorus atom were designed,synthesized,characterized and investigated in Ni-and Pd-catalyzed ethylene polymerization.The structure of th...A series of phosphine-sulfonate ligands bearing 2-,3-and 4-vinylphenyl on the phosphorus atom were designed,synthesized,characterized and investigated in Ni-and Pd-catalyzed ethylene polymerization.The structure of the phosphine-sulfonate Pd complex bearing 2-vinylphenyl on the phosphorus atom showed 2,1-insertion for the 2-vinyl group.The phosphine-sulfonate Ni complex bearing 2-vinylphenyl resulted in significantly increased thermal stability and polyethylene molecular weights(Mn=3.69×10^(4)g·mol^(-1) at 80℃)versus the counterparts bearing 3-/4-vinyl groups as well as previously reported phosphine-sulfonate Ni complexes bearing bulky biaryl substituents.展开更多
A new polymer-supported metallocene catalyst has been prepared, The polymer-supported metallocene displayed considerably high activity in ethylene polymerization, the highest being 3.62x10(7) gPE/molZr.h, the molecula...A new polymer-supported metallocene catalyst has been prepared, The polymer-supported metallocene displayed considerably high activity in ethylene polymerization, the highest being 3.62x10(7) gPE/molZr.h, the molecular weight of the polyethylene produced was Mn = 1.29x10(5). about 3-4 times those of corresponding homogeneous zirconocenes. The polymer-supported metallocene keeps the characteristics of homogeneous metallocene catalysts, and offers some features, such as adaptable to gas phase and slurry processes: easy to prepare in low cost: relatively high activity and lower MAO/Zr ratio; lower inorganic residues in the polyolefins as compared to cases of SiO2, Al2O3 or MgCl2; unitary active structure, no complex surface as with SiO2; good control of morphology of the resulting polymer.展开更多
A silica-supported Ziegler-Natta catalyst with dimethyldichlorosilane （DMDS） as modifier and small silica as support was successfully prepared and characterized. Results from pilot screen showed that the new catalys...A silica-supported Ziegler-Natta catalyst with dimethyldichlorosilane （DMDS） as modifier and small silica as support was successfully prepared and characterized. Results from pilot screen showed that the new catalyst exhibited higher catalytic activity, better hydrogen response ability and better copolymerization ability than the commercial M catalyst. Pilot screen in ethylene gas phase fluidized bed polymerization, the catalytic activity of the new catalyst was up to 8000 g PE/g cat, which was twice of that of the commercial M catalyst. The bulk density of polyethylene obtained with the new catalyst was 0.38 g/cm^3. The new catalyst is suitable for condensed and super-condensed process in fluidized bed ethylene polymerization.展开更多
In order to promote the thermostability of a-diimine nickel complex by ligand backbone structure,a series of α-diimine nickel complexes with substituents on acenaphthequinone backbone were synthesized and used as cat...In order to promote the thermostability of a-diimine nickel complex by ligand backbone structure,a series of α-diimine nickel complexes with substituents on acenaphthequinone backbone were synthesized and used as catalysts for ethylene polymerization.When the hydroxyethyl phenoxyl group was introduced to the acenaphthequinone-backbone,the thermal stability and activity of the catalyst could be significantly improved.The catalytic activity of complex C2[5-(4-(2-hydroxyethyl)phenoxyl)-N,N-bis(2,6-diisopropyl)acenaphthylene-1,2-diimine]nickel(Ⅱ)dibromide with isopropyl substituents on N-aryl reached 8.2×10^6g/(molNi·h)at 70℃and 2 MPa.The activity of[5-(4-(2-hydroxyethyl)phenoxyl)-N,N-bis(2,6-dibenzhydryl-4-menthylphenyl)acenaphthylene-1,2-diimine]nickel(Ⅱ)dibromide(C3)still maintained at 6.7×10^5 g/(molNi·h)at 120℃.Compared with C3 containing bulky dibenzhydryl substituents,the activity of C2 was sensitive to the change of the polymerization pressure.However,the polyethylenes obtained from complex C3 had lower branching density.Meanwhile,the molecular weight could reach 971 kg/mol,which is almost 5 times as much as that of the polyethylene obtained from complex C2.展开更多
A series of new nickel(Ⅱ)complexes with 2-aminomethylpyridine ligands,(2-PyCH_2NHAr)_2NiBr_2(Ar=2,6- dimethylphenyl 2a;2,6-diisopropylphenyl 2b,2,6-difluorophenyl 2c),have been synthesized and used as catalyst precur...A series of new nickel(Ⅱ)complexes with 2-aminomethylpyridine ligands,(2-PyCH_2NHAr)_2NiBr_2(Ar=2,6- dimethylphenyl 2a;2,6-diisopropylphenyl 2b,2,6-difluorophenyl 2c),have been synthesized and used as catalyst precursors for ethylene polymerization in the presence of methylaluminoxane(MAO).The catalysts containing ortho-alkyl-substituents afford high molecular weight branched polyethylenes as well as a certain amount of oligomers.Enhancing the steric bulk of the alkyl substituent of the catalyst resulted in...展开更多
Polyethylene (PE) grafting 4-vinylpyridine copolymers has been produced as powders of different rushes by theirradiation method. After treatment with methylaluminoxane (MAO), the copolymers were used as supports for C...Polyethylene (PE) grafting 4-vinylpyridine copolymers has been produced as powders of different rushes by theirradiation method. After treatment with methylaluminoxane (MAO), the copolymers were used as supports for Cp_2ZrCl_2catalyst Results of X-ray photoelectron spectroscopy, Fourier transforms infrared spectroscopy, ultraviolet spectroscopy andscanning electron microscope measurements show that the catalytic sites have been linked through MAO on the PE-graft-4-vinylpyridine (PEVP). The percentages of grafting 4-vinylpyridine and supported Cp_2ZrCl_2 depend on the size ofpolyethylene powder. The smaller the polyethylene powder, the more percent of 4-vinylpyridine groups and Cp_2ZrCl_2 existon the polyethylene chains, and the PEVP-supported catalyst has a relatively high activity for ethylene polymerization.展开更多
A nickel-diimine catalyst [N, N'-bis(2,6-diisopropylphenyl)-1,4-diaza-2,3-dimethyl-1, 3-butadiene nickel dibromide, DMN] was supported on palygorskite clay for ethylene slurry polymerization. The effect of support...A nickel-diimine catalyst [N, N'-bis(2,6-diisopropylphenyl)-1,4-diaza-2,3-dimethyl-1, 3-butadiene nickel dibromide, DMN] was supported on palygorskite clay for ethylene slurry polymerization. The effect of supporting methods on the catalyst impregnation was studied and compared. Pretreatment of the support with methylalumi-noxane (MAO) followed by DMN impregnation gave higher catalyst loading and catalytic activity than the direct impregnation of DMN. Catalyst activity as high as 5.42×105g PE·molNi-1·h-1 was achieved at ethylene pressure of 6.87×105 Pa and polymerization temperature of 20℃. In particular, the morphological change of the support during MAO treatment was characterized and analyzed. It was found that nano-fiber clusters formed during the support pretreatment, which increased the surface area of the support and favored the impregnation of the catalyst. The investigation of polymerization behavior of supported catalyst revealed that the polymerization rate could be kept at a relatively high level for a long time, different from the homogeneous catalyst. By analyzing the SEM photographs of the polymer produced by the supported catalyst, the morphological evolution of polymer particles was preliminarily studied.展开更多
The efficient copolymerization of olefin with polar monomers using nickel-based catalysts presents a longstanding challenge. In this contribution, three phosphine-benzocyclone ligands and corresponding neutral nickel ...The efficient copolymerization of olefin with polar monomers using nickel-based catalysts presents a longstanding challenge. In this contribution, three phosphine-benzocyclone ligands and corresponding neutral nickel catalysts(Ni1: Ar = Ph;Ni2: Ar = 2-(C_(6)H_(5))C_(6)H_(4);Ni3: Ar = 2-[2',6'-(Me O)_(2)-C_(6)H3]C_(6)H_(4)) were prepared and applied for the ethylene polymerization and copolymerization with polar monomers without any cocatalyst. The bulky substituent groups in complexes Ni2 and Ni3 contributed to high catalytic activities(up to 7.24×10^(6) and 9.04×10^(6)g·mol Ni^(-1)·h^(-1), respectively), and produced high-molecular-weight polyethylene(Mw up to 545.7 k Da). Complex Ni3 exhibited high activities for ethylene polymerization at the level of 10^(6) g·mol Ni^(-1)·h^(-1) across a wide range from 30 ℃ to 120 ℃, exhibiting excellent high temperature tolerance. These nickel complexes were also effectively employed in the copolymerization of ethylene with methyl acrylate, ethyl acrylate, butyl acrylate and lauryl acrylate, producing copolymers with high molecular weights(Mw up to 80.5 k Da) and high polar monomer incorporation(up to 8.2 mol%). Microstructure analyses revealed that the introduction of large sterically hindered substituents facilitated the incorporation of polar functional units into the polymer backbone. This study demonstrates the potential of these nickel-based catalysts for efficient copolymerization of olefin with polar monomers.展开更多
5,6,7-Trihydroquinolin-8-one was condensed with the corresponding benzidine to give N,N′-bis（5,6,7-trihydroquinolin-8-ylidene）-[1,1′-biphenyl]-4,4′-diamine derivatives（L1–L3）. The ligands were reacted with two...5,6,7-Trihydroquinolin-8-one was condensed with the corresponding benzidine to give N,N′-bis（5,6,7-trihydroquinolin-8-ylidene）-[1,1′-biphenyl]-4,4′-diamine derivatives（L1–L3）. The ligands were reacted with two equivalents of Ni Cl2·6H2O in a mixture of Et OH and CH2Cl2 to afford the corresponding dinickel（II） chloride complexes（Ni1-Ni3）. The organic compounds were completely characterized, whilst the bi-metallic complexes were characterized by FTIR spectra and elemental analysis. These nickel complexes exhibited high activities towards ethylene polymerization in the presence of either MAO or Me2AlCl, maintaining a high activity over a prolonged period. The obtained polyethylenes were confirmed as having low molecular weights by GPC analysis.展开更多
Two novel heterogeneous nickel a-diimine based polymerization catalysts, containing MWCNT as the main ligand, were synthesized by novel in situ catalyst preparation technique. The in situ synthesis was performed by co...Two novel heterogeneous nickel a-diimine based polymerization catalysts, containing MWCNT as the main ligand, were synthesized by novel in situ catalyst preparation technique. The in situ synthesis was performed by covalent attachment of the acenaphthenic ligand core to amine functionalized MWCNT ligand arms through diimine bonding and further nickel dibromide chelation. The prepared catalysts were fully characterized and their structures and supporting efficiencies were determined. Single or double introduction of the MWCNTs through their ends or sidewall（s） in the catalytic system, as a ligand, influenced the catalytic performance, microstructure and morphology of obtained polyethylenes. MWCNT sidewall bonding to para-aryl position of the tetramethylphenyl moiety performed as more electron-donating ligand than MWCNT ends linked to the imine bond and protected the catalytic system to retain its activity. This character resulted in the maintenance of the resulting polymer topology at elevated temperatures so that the catalytic activity and the obtained polymer melting points remained around 110 g PE·mmol^-1 Ni·h^-1 and 123 ℃ in all polymerization temperatures respectively. In polymerization trials, molecular weight fall against temperature was not as sharp as what had been observed in sequentially prepared catalysts insofar as the molecular weight of resultant polymer at 60 ℃ reached to 310000 g·mol^-1 which was close to the highest value had been reported at 30 ℃ for sequentially prepared catalysts. TEM observations showed the presence of the stopped-growth polymer chains due to geometrical constrains or ligand debonding for both catalytic systems.展开更多
A series of half-sandwich group IV metal complexes with tridentate monoanionic phenoxy-imine arylsulfide [O-NS] ligand [2-Bu^t4-Me-6-（（2-（SC6H5）C6H4N = CHC6H2O）]- （La） and dianionic phenoxy-amine arylsulfide [O...A series of half-sandwich group IV metal complexes with tridentate monoanionic phenoxy-imine arylsulfide [O-NS] ligand [2-Bu^t4-Me-6-（（2-（SC6H5）C6H4N = CHC6H2O）]- （La） and dianionic phenoxy-amine arylsulfide [O-N-S] ligand [2-Bu^t4-Me-6-（（2-（SC6H5）C6H4N-CH2C6H2O）]2- （Lb） have been synthesized and characterized. Lb was obtained easily in high yield by reduction of ligand La with excess LiAlH4 in cool diethyl ether. Half-sandwich Group Ⅳ metal complexes CpTi[O-NS]Cl2 （1a）, CpZr[O-NS]Cl2 （1b）, CpTi[O-N-S]Cl （2a）, CpZr[O-N-S]Cl （2b） and CpZr[O-N-S]Cl （2c） were synthesized by the reactions of La and Lb with CpTiCl3, CpZrCl3 and Cp ZrCl3, and characterized by IR, ^1H-NMR, ^13C-NMR and elemental analysis. In addition, an X-ray structure analysis was performed on ligand Lb. The title Group IV half-sandwich bearing tridentate [O,N,S] ligands show good catalytic activities for ethylene polymerization in the presence of methylaluminoxane （MAO） as co-catalyst up to 1.58 × 10^7 g-PE.mol-Zr-1.h-1. The good catalytic activities can be maintained even at high temperatures such as 100 ℃ exhibiting the excellent thermal stability for these half-sandwich metal pre-catalysts.展开更多
Several novel mono（β-enaminoketonato） vanadium complexes bearing constrained [（C6Hs）C6H3C（O）=C（CH2）nCH=N-Ar]VCl2（THF）2 （V3a： n = 1, Ar = C6H5; V4a： n = 2, Ar cyclic skeleton, including C6H5; V4b： n = 2,...Several novel mono（β-enaminoketonato） vanadium complexes bearing constrained [（C6Hs）C6H3C（O）=C（CH2）nCH=N-Ar]VCl2（THF）2 （V3a： n = 1, Ar = C6H5; V4a： n = 2, Ar cyclic skeleton, including C6H5; V4b： n = 2, Ar C6F5; V4c： n = 2, Ar = （C3H7）2C6H3; V5a： n = 3, Ar = C6H5）, were synthesized and their structure and properties were characterized. The structures of V4c and V5a in solid-state were further confirmed by X-ray crystallographic analysis. Density functional theory （DFT） results indicated that these complexes showed enhanced steric hindrance around the metal center as compared with the acyclic analogues. Upon activation with Et2AlCl and in the presence of ethyl trichloroacetate as a reactivator, all of the complexes exhibited high catalytic activities （107 gPE/（molv.h）） toward ethylene polymerization, and the obtained polymers exhibited unimodal distributions （Mw/Mn = 2.0-2.3） even produced at elevated temperatures （70-100 ℃） and prolonged reaction time. When MAO was employed as a cocatalyst, they only showed moderate catalytic activities （10^5 gPE/（molv·h））, but the resulting polymers had higher molecular weights （168-241 kg/mol）. These vanadium complexes with cyclic skeleton also showed high catalytic activities toward ethylene/norbornene copolymerization. The produced copolymers displayed approximate alternating structure at high in-feed concentration of norbornene. The catalytic capabilities of these complexes could be tuned conveniently by varying ligand structure. Furthermore, the cyclic voltammetry results also proved that these complexes exhibited better redox stabilities than the complexes bearing linear skeleton.展开更多
A group of five bis(arylimino)pyridine-cobalt(Ⅱ)chloride complexes,[2-{(2,6-(Ph_(2)CH)_(2)-4-MeOC_(6)H_(2))N=CMe}-6-(ArN=CMe)C_5 H_(3)N]CoCl_(2)(Ar=2,6-Me_(2)C_(6)H_(3)Co1,2,6-Et_(2)C_(6)H_(3)Co2,2,6-iPr_(2)C_(6)H_(3...A group of five bis(arylimino)pyridine-cobalt(Ⅱ)chloride complexes,[2-{(2,6-(Ph_(2)CH)_(2)-4-MeOC_(6)H_(2))N=CMe}-6-(ArN=CMe)C_5 H_(3)N]CoCl_(2)(Ar=2,6-Me_(2)C_(6)H_(3)Co1,2,6-Et_(2)C_(6)H_(3)Co2,2,6-iPr_(2)C_(6)H_(3)Co3,2,4,6-Me_(3)C_(6)H_(2)Co4,2,6-Et_(2)-4-MeC_(6)H_(2)Co5),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 by^(1)H-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(6.92×10^(6)g_(PE)·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=6.29×10^(5)g·mol^(-1)).All the polymers displayed high linearity as demonstrated by their melting temperatures(>130℃)and their~1 H-and^(13)C-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.展开更多
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 act...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.展开更多
The article describes ethylene polymerization reactions with transition metal catalysts based on complexes of CoCl_(2) and FeCl_(2) with an N,N,N-tridentate ligand 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine. Th...The article describes ethylene polymerization reactions with transition metal catalysts based on complexes of CoCl_(2) and FeCl_(2) with an N,N,N-tridentate ligand 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine. The complexes are converted into polymerization catalysts by reacting them either with polymethylalumoxane (MAO) or with a combination of Al(C2H5)2Cl and Mg(C4H9)2 at an [Al]:[Mg] ratio of ~3. Both MAO-activated complexes readily polymerize ethylene at 35 ℃ with the formation of linear, low molecular weight polymers with a narrow molecular weight distribution. The same complexes, when activated with the Al(C2H5)2Cl-Mg(C4H9)2 combination, form multi-center catalysts and generate polyethylenes with a broad molecular weight distribution.展开更多
The external stimulus response strategy has been evolved rapidly in the field of olefin polymerization.In this work,we modularly synthesized three types of double stimulus responsiveα-diimine palladium catalysts,comb...The external stimulus response strategy has been evolved rapidly in the field of olefin polymerization.In this work,we modularly synthesized three types of double stimulus responsiveα-diimine palladium catalysts,combining redox regulation and other regulation together,such as light,Lewis acid and alkali cations.The catalytic activities and the molecular weight of polyethylene products can be regulated for 4 times in ethylene polymerization.These palladium complexes were also used for the copolymerization reaction of ethylene and polar monomers,such as methyl 10-undecylenate and methyl acrylate,effectively regulating the catalytic activities,the molecular weight and polar monomer incorporation of the prepared copolymers.The research on these dual-regulated palladium complexes makes full use of prepared catalysts and provides new inspirations for regulating olefin polymerization.展开更多
The N,N,N'-ferrous chloride complexes,[2-{CMeN(2,4-(CHPh)_(2)-6-FC_(6)H_(2))}-6-(CMeNAr)C_(5)H_(3)N]FeCl_(2)(Ar=2,6-Me_(2)C_(6)H_(3) Fe1,2,6-Et_(2)C_(6)H_(3)Fe2,2,6-^(i)Pr_(2)C_(6)H_(3) Fe3,2,4,6-Me_(3)C_(6)H_(2) ...The N,N,N'-ferrous chloride complexes,[2-{CMeN(2,4-(CHPh)_(2)-6-FC_(6)H_(2))}-6-(CMeNAr)C_(5)H_(3)N]FeCl_(2)(Ar=2,6-Me_(2)C_(6)H_(3) Fe1,2,6-Et_(2)C_(6)H_(3)Fe2,2,6-^(i)Pr_(2)C_(6)H_(3) Fe3,2,4,6-Me_(3)C_(6)H_(2) Fe4 and 2,6-Et_(2)-4-MeC_(6)H_(2) Fe5),each possessing one N-2,4-dibenzhydryl-6-fluorophenyl group,were readily synthesized from their respective unsymmetrical bis(imino)pyridines,L1-L5.Structural identification of Fe2 highlighted the variation in the steric properties provided by the dissimilar N-aryl groups.Following pre-treatment with either MAO or MMAO,complexes Fe1-Fe5 all displayed,at an operating temperature of 80℃,high activities for ethylene polymerization with levels falling in the order:Fe4> Fe1> Fe5> Fe2> Fe3.Notably,Fe4/MAO displayed the highest activity of 1.94×10^(7) g_(PE)·mol_(Fe)^(-1)·h^(-1) of the study with only a modest loss in performance at 90℃.Generally,the resulting polyethylenes were highly linear(T_(m) range:122-132℃),narrowly disperse and of low molecular weight(M_(w) range:6.73-46.04kg·mol^(-1)),with the most sterically hindered Fe3 forming the highest molecular weight polymer of the series.End-group analysis by ^(1)H-and ^(13)CNMR spectroscopy revealed saturated alkyl(n-propyl and i-propyl) and unsaturated vinyl chain ends indicative of the role of both β-H elimination and chain transfer to aluminum as termination pathways.By comparison with previou sly reported iron precatalysts with similar tridentate ligand skeletons,it is evident that the introduction of a large benzhydryl group in combination with a fluorine as the ortho-substituents of one N-aryl group has the effect of enhancing thermal stability of the iron polymerization catalyst whilst maintaining appreciable polymer molecular weight.展开更多
This contribution reports ethylene polymerization behavior of titanium complexes incorporating bis（phenoxyimine） ligands. Six phenoxy-imine Ti（IV） complexes {6-R^1-2-[CH=N（2,6-difluoro-3,5-diR^2-4-R^3Ph）]C6H30}2...This contribution reports ethylene polymerization behavior of titanium complexes incorporating bis（phenoxyimine） ligands. Six phenoxy-imine Ti（IV） complexes {6-R^1-2-[CH=N（2,6-difluoro-3,5-diR^2-4-R^3Ph）]C6H30}2TiCl2 （1： R^1 = H, R^2 = H, R^3 = H; 2： R^1 = H, R^2 = H, R%3 = 4-vinylphenyl; 3： R^1 = CH3, R^2 = H, R^3 = H; 4： R^1 = CH3, R^2 = H, R^3 = 4-vinylphenyl; 5： R^1 = CH3, R^2 = F, R^3 = H; 6： R^1 = CH3, R^2 = F, R^3 = 4-vinylphenyl） have been synthesized and evaluated for ethylene polymerization using dried MAO （simplified as DMAO） as cocatalyst. An obvious catalytic heterogeneity of Cat 2 （Complex 2/DMAO） towards ethylene polymerization was observed, which was illustrated by decreased activity, multi- modal molecular weight distribution and partially improved particle morphology comparing with Cat 1. Moreover, Cat 3 exhibits ＂living＂ characteristics in the process under certain conditions （25 ~C, less than 20 min）. Otherwise, the moderate to high ethylene polymerization activity of ca. 105-106 g PE/（mol Ti＇h） and high molecular weight （Mw = 105-106） of polyethylene can be obtained by changing the skeleton structure of these complexes.展开更多
基金financially supported by the National Natural Science Foundation of China(No.21172269)the Fundamental Research Funds for the Central Universities,SouthCentral Minzu University(No.CZH24005)。
文摘Binuclear complexes have attracted extensive attention in fields such as catalysis because of their likely bimetallic synergistic effect;however,the mechanism and factors influencing this synergism remain unclear.In this work,six bis-β-ketoimine binuclear titanium complexes4a-4f containing different alkylthio sidearms and configurations were synthesized and characterized by nuclear magnetic resonance hydrogen spectrum(~1H-NMR),nuclear magnetic resonance carbon spectrum(^(13)C-NMR),Fourier transform infrared spectrum(FTIR),and elemental analysis.The intermetallic distances of isomeric complexes 4a,4d,4e and 4f determined through density functional theory(DFT)optimization were in the order 4a<4d<4e<4f and were found to significantly influence the catalytic performance for ethylene(co)polymerization.These complexes could efficiently catalyze ethylene polymerization and ethylene/1-hexene or ethylene/1-octene copolymerization with high activity to produce highmolecular-weight ethylene homo-and co-polymers.Among the three binuclear titanium complexes 4a-4c with similar structures but different lengths of alkylthio sidearms,complex 4a,which contained the shortest methylthio sidearm,exhibited the highest activity for ethylene polymerization and copolymerization with 1-hexene or 1-octene.Additionally,for ethylene/1-hexene or ethylene/1-octene copolymerization,it showed the highest comonomer incorporation compared with propylthio(4b)and octylthio(4c)derivatives because of the smaller steric hindrance of the methyl group in 4a and the more open coordination space for vinyl monomers.Furthermore,among the isomeric complexes 4a,4d,4e and4f,complex 4a with the shortest bimetallic distance also exhibited the highest activity towards ethylene(co)polymerization,and the highest 1-hexene or 1-octene incorporation in comparison with its regioisomeric counterparts 4d,4e and p-phenyl-bridged analog 4f,owing to a more appropriate bimetallic distance that is conducive to a synergistic effect.
基金supported by the State Key Research Development Program of China(No.2021YFB3800701)National Natural Science Foundation of China(NSFC,No.52173016)+2 种基金Guangdong Basic and Applied Basic Research Foundation(Nos.2024A1515012784,2024A1515011102,and 2023A1515110549)Fundamental Research Funds for the Central Universities,Sun Yat-sen University(No.24qnpy047)PetroChina Scientific and Technological Projects(No.2022DJ6308).
文摘A series of“half-sandwich”bis(imino)pyridyl iron complexes with a substituted 8-(p-Xphenyl)naphthylamine(X=OMe,Me,CF3)was designed and synthesized by combining weakπ-πinteraction with steric and electronic tunings.The weak noncovalentπ-πinteraction as well as the steric and electronic effects of bis(imino)pyridyl iron complexes were identified by experimental analyses and calculations.The roles of weakπ-πinteraction,steric bulk,and electronic tuning on the ethylene polymerization performance of bis(imino)pyridyl iron catalysts were studied in detail.The combination ofπ-πinteraction with steric and electronic tunings can access to thermally stable bis(imino)pyridyl iron at 130°C.
基金supported by the National Natural Science Foundation of China(Nos.21690071,21871242,U19B6001,U1904212)K.C.Wong Education Foundation.
文摘A series of phosphine-sulfonate ligands bearing 2-,3-and 4-vinylphenyl on the phosphorus atom were designed,synthesized,characterized and investigated in Ni-and Pd-catalyzed ethylene polymerization.The structure of the phosphine-sulfonate Pd complex bearing 2-vinylphenyl on the phosphorus atom showed 2,1-insertion for the 2-vinyl group.The phosphine-sulfonate Ni complex bearing 2-vinylphenyl resulted in significantly increased thermal stability and polyethylene molecular weights(Mn=3.69×10^(4)g·mol^(-1) at 80℃)versus the counterparts bearing 3-/4-vinyl groups as well as previously reported phosphine-sulfonate Ni complexes bearing bulky biaryl substituents.
文摘A new polymer-supported metallocene catalyst has been prepared, The polymer-supported metallocene displayed considerably high activity in ethylene polymerization, the highest being 3.62x10(7) gPE/molZr.h, the molecular weight of the polyethylene produced was Mn = 1.29x10(5). about 3-4 times those of corresponding homogeneous zirconocenes. The polymer-supported metallocene keeps the characteristics of homogeneous metallocene catalysts, and offers some features, such as adaptable to gas phase and slurry processes: easy to prepare in low cost: relatively high activity and lower MAO/Zr ratio; lower inorganic residues in the polyolefins as compared to cases of SiO2, Al2O3 or MgCl2; unitary active structure, no complex surface as with SiO2; good control of morphology of the resulting polymer.
基金supported by the Program for New Century Excellent Talents in Universities(NCET-07-0142)the Program for New Century Excellent Talents in Heilongjiang Provincial Universities(NCET-06-010)+1 种基金the National Natural Science Foundation of China(No.20972025)the Science Foundation of Tianjin University of Science & Technology(No.20090420).
文摘A silica-supported Ziegler-Natta catalyst with dimethyldichlorosilane （DMDS） as modifier and small silica as support was successfully prepared and characterized. Results from pilot screen showed that the new catalyst exhibited higher catalytic activity, better hydrogen response ability and better copolymerization ability than the commercial M catalyst. Pilot screen in ethylene gas phase fluidized bed polymerization, the catalytic activity of the new catalyst was up to 8000 g PE/g cat, which was twice of that of the commercial M catalyst. The bulk density of polyethylene obtained with the new catalyst was 0.38 g/cm^3. The new catalyst is suitable for condensed and super-condensed process in fluidized bed ethylene polymerization.
基金the National Natural Science Foundation of China(Nos.21004017 and 21004043)the Natural Science Foundation of Hebei Provinee(No.B2015202049).
文摘In order to promote the thermostability of a-diimine nickel complex by ligand backbone structure,a series of α-diimine nickel complexes with substituents on acenaphthequinone backbone were synthesized and used as catalysts for ethylene polymerization.When the hydroxyethyl phenoxyl group was introduced to the acenaphthequinone-backbone,the thermal stability and activity of the catalyst could be significantly improved.The catalytic activity of complex C2[5-(4-(2-hydroxyethyl)phenoxyl)-N,N-bis(2,6-diisopropyl)acenaphthylene-1,2-diimine]nickel(Ⅱ)dibromide with isopropyl substituents on N-aryl reached 8.2×10^6g/(molNi·h)at 70℃and 2 MPa.The activity of[5-(4-(2-hydroxyethyl)phenoxyl)-N,N-bis(2,6-dibenzhydryl-4-menthylphenyl)acenaphthylene-1,2-diimine]nickel(Ⅱ)dibromide(C3)still maintained at 6.7×10^5 g/(molNi·h)at 120℃.Compared with C3 containing bulky dibenzhydryl substituents,the activity of C2 was sensitive to the change of the polymerization pressure.However,the polyethylenes obtained from complex C3 had lower branching density.Meanwhile,the molecular weight could reach 971 kg/mol,which is almost 5 times as much as that of the polyethylene obtained from complex C2.
基金the National Natural Science Foundation of China(Nos.20674097,20734004)the Ministry of Education of China(Foundation for Ph.D.Training).
文摘A series of new nickel(Ⅱ)complexes with 2-aminomethylpyridine ligands,(2-PyCH_2NHAr)_2NiBr_2(Ar=2,6- dimethylphenyl 2a;2,6-diisopropylphenyl 2b,2,6-difluorophenyl 2c),have been synthesized and used as catalyst precursors for ethylene polymerization in the presence of methylaluminoxane(MAO).The catalysts containing ortho-alkyl-substituents afford high molecular weight branched polyethylenes as well as a certain amount of oligomers.Enhancing the steric bulk of the alkyl substituent of the catalyst resulted in...
基金National Natural Science Foundation of China (No. 20272062)
文摘Polyethylene (PE) grafting 4-vinylpyridine copolymers has been produced as powders of different rushes by theirradiation method. After treatment with methylaluminoxane (MAO), the copolymers were used as supports for Cp_2ZrCl_2catalyst Results of X-ray photoelectron spectroscopy, Fourier transforms infrared spectroscopy, ultraviolet spectroscopy andscanning electron microscope measurements show that the catalytic sites have been linked through MAO on the PE-graft-4-vinylpyridine (PEVP). The percentages of grafting 4-vinylpyridine and supported Cp_2ZrCl_2 depend on the size ofpolyethylene powder. The smaller the polyethylene powder, the more percent of 4-vinylpyridine groups and Cp_2ZrCl_2 existon the polyethylene chains, and the PEVP-supported catalyst has a relatively high activity for ethylene polymerization.
基金Supported by the National Natural Science Foundation of China (No. 20376069).
文摘A nickel-diimine catalyst [N, N'-bis(2,6-diisopropylphenyl)-1,4-diaza-2,3-dimethyl-1, 3-butadiene nickel dibromide, DMN] was supported on palygorskite clay for ethylene slurry polymerization. The effect of supporting methods on the catalyst impregnation was studied and compared. Pretreatment of the support with methylalumi-noxane (MAO) followed by DMN impregnation gave higher catalyst loading and catalytic activity than the direct impregnation of DMN. Catalyst activity as high as 5.42×105g PE·molNi-1·h-1 was achieved at ethylene pressure of 6.87×105 Pa and polymerization temperature of 20℃. In particular, the morphological change of the support during MAO treatment was characterized and analyzed. It was found that nano-fiber clusters formed during the support pretreatment, which increased the surface area of the support and favored the impregnation of the catalyst. The investigation of polymerization behavior of supported catalyst revealed that the polymerization rate could be kept at a relatively high level for a long time, different from the homogeneous catalyst. By analyzing the SEM photographs of the polymer produced by the supported catalyst, the morphological evolution of polymer particles was preliminarily studied.
基金financially supported by the National Natural Science Foundation of China (No. 52130307)。
文摘The efficient copolymerization of olefin with polar monomers using nickel-based catalysts presents a longstanding challenge. In this contribution, three phosphine-benzocyclone ligands and corresponding neutral nickel catalysts(Ni1: Ar = Ph;Ni2: Ar = 2-(C_(6)H_(5))C_(6)H_(4);Ni3: Ar = 2-[2',6'-(Me O)_(2)-C_(6)H3]C_(6)H_(4)) were prepared and applied for the ethylene polymerization and copolymerization with polar monomers without any cocatalyst. The bulky substituent groups in complexes Ni2 and Ni3 contributed to high catalytic activities(up to 7.24×10^(6) and 9.04×10^(6)g·mol Ni^(-1)·h^(-1), respectively), and produced high-molecular-weight polyethylene(Mw up to 545.7 k Da). Complex Ni3 exhibited high activities for ethylene polymerization at the level of 10^(6) g·mol Ni^(-1)·h^(-1) across a wide range from 30 ℃ to 120 ℃, exhibiting excellent high temperature tolerance. These nickel complexes were also effectively employed in the copolymerization of ethylene with methyl acrylate, ethyl acrylate, butyl acrylate and lauryl acrylate, producing copolymers with high molecular weights(Mw up to 80.5 k Da) and high polar monomer incorporation(up to 8.2 mol%). Microstructure analyses revealed that the introduction of large sterically hindered substituents facilitated the incorporation of polar functional units into the polymer backbone. This study demonstrates the potential of these nickel-based catalysts for efficient copolymerization of olefin with polar monomers.
基金financially supported by the National Natural Science Foundation of China (Nos. 21374123 and U1362204)
文摘5,6,7-Trihydroquinolin-8-one was condensed with the corresponding benzidine to give N,N′-bis（5,6,7-trihydroquinolin-8-ylidene）-[1,1′-biphenyl]-4,4′-diamine derivatives（L1–L3）. The ligands were reacted with two equivalents of Ni Cl2·6H2O in a mixture of Et OH and CH2Cl2 to afford the corresponding dinickel（II） chloride complexes（Ni1-Ni3）. The organic compounds were completely characterized, whilst the bi-metallic complexes were characterized by FTIR spectra and elemental analysis. These nickel complexes exhibited high activities towards ethylene polymerization in the presence of either MAO or Me2AlCl, maintaining a high activity over a prolonged period. The obtained polyethylenes were confirmed as having low molecular weights by GPC analysis.
文摘Two novel heterogeneous nickel a-diimine based polymerization catalysts, containing MWCNT as the main ligand, were synthesized by novel in situ catalyst preparation technique. The in situ synthesis was performed by covalent attachment of the acenaphthenic ligand core to amine functionalized MWCNT ligand arms through diimine bonding and further nickel dibromide chelation. The prepared catalysts were fully characterized and their structures and supporting efficiencies were determined. Single or double introduction of the MWCNTs through their ends or sidewall（s） in the catalytic system, as a ligand, influenced the catalytic performance, microstructure and morphology of obtained polyethylenes. MWCNT sidewall bonding to para-aryl position of the tetramethylphenyl moiety performed as more electron-donating ligand than MWCNT ends linked to the imine bond and protected the catalytic system to retain its activity. This character resulted in the maintenance of the resulting polymer topology at elevated temperatures so that the catalytic activity and the obtained polymer melting points remained around 110 g PE·mmol^-1 Ni·h^-1 and 123 ℃ in all polymerization temperatures respectively. In polymerization trials, molecular weight fall against temperature was not as sharp as what had been observed in sequentially prepared catalysts insofar as the molecular weight of resultant polymer at 60 ℃ reached to 310000 g·mol^-1 which was close to the highest value had been reported at 30 ℃ for sequentially prepared catalysts. TEM observations showed the presence of the stopped-growth polymer chains due to geometrical constrains or ligand debonding for both catalytic systems.
基金financially supported by the Shanghai Science and Technology Committee(08DZ2270500,08DJ1400103)Shanghai Leading Academic Discipline Project(B108)the National Basic Research Program of China(2009CB825300,2010DFA41160)
文摘A series of half-sandwich group IV metal complexes with tridentate monoanionic phenoxy-imine arylsulfide [O-NS] ligand [2-Bu^t4-Me-6-（（2-（SC6H5）C6H4N = CHC6H2O）]- （La） and dianionic phenoxy-amine arylsulfide [O-N-S] ligand [2-Bu^t4-Me-6-（（2-（SC6H5）C6H4N-CH2C6H2O）]2- （Lb） have been synthesized and characterized. Lb was obtained easily in high yield by reduction of ligand La with excess LiAlH4 in cool diethyl ether. Half-sandwich Group Ⅳ metal complexes CpTi[O-NS]Cl2 （1a）, CpZr[O-NS]Cl2 （1b）, CpTi[O-N-S]Cl （2a）, CpZr[O-N-S]Cl （2b） and CpZr[O-N-S]Cl （2c） were synthesized by the reactions of La and Lb with CpTiCl3, CpZrCl3 and Cp ZrCl3, and characterized by IR, ^1H-NMR, ^13C-NMR and elemental analysis. In addition, an X-ray structure analysis was performed on ligand Lb. The title Group IV half-sandwich bearing tridentate [O,N,S] ligands show good catalytic activities for ethylene polymerization in the presence of methylaluminoxane （MAO） as co-catalyst up to 1.58 × 10^7 g-PE.mol-Zr-1.h-1. The good catalytic activities can be maintained even at high temperatures such as 100 ℃ exhibiting the excellent thermal stability for these half-sandwich metal pre-catalysts.
基金the National Natural Science Foundation of China(No.21234006)China National High-tech R&D Program(No.2015AA034002)
文摘Several novel mono（β-enaminoketonato） vanadium complexes bearing constrained [（C6Hs）C6H3C（O）=C（CH2）nCH=N-Ar]VCl2（THF）2 （V3a： n = 1, Ar = C6H5; V4a： n = 2, Ar cyclic skeleton, including C6H5; V4b： n = 2, Ar C6F5; V4c： n = 2, Ar = （C3H7）2C6H3; V5a： n = 3, Ar = C6H5）, were synthesized and their structure and properties were characterized. The structures of V4c and V5a in solid-state were further confirmed by X-ray crystallographic analysis. Density functional theory （DFT） results indicated that these complexes showed enhanced steric hindrance around the metal center as compared with the acyclic analogues. Upon activation with Et2AlCl and in the presence of ethyl trichloroacetate as a reactivator, all of the complexes exhibited high catalytic activities （107 gPE/（molv.h）） toward ethylene polymerization, and the obtained polymers exhibited unimodal distributions （Mw/Mn = 2.0-2.3） even produced at elevated temperatures （70-100 ℃） and prolonged reaction time. When MAO was employed as a cocatalyst, they only showed moderate catalytic activities （10^5 gPE/（molv·h））, but the resulting polymers had higher molecular weights （168-241 kg/mol）. These vanadium complexes with cyclic skeleton also showed high catalytic activities toward ethylene/norbornene copolymerization. The produced copolymers displayed approximate alternating structure at high in-feed concentration of norbornene. The catalytic capabilities of these complexes could be tuned conveniently by varying ligand structure. Furthermore, the cyclic voltammetry results also proved that these complexes exhibited better redox stabilities than the complexes bearing linear skeleton.
基金financially supported by the National Natural Science Foundation of China(No.21871275)。
文摘A group of five bis(arylimino)pyridine-cobalt(Ⅱ)chloride complexes,[2-{(2,6-(Ph_(2)CH)_(2)-4-MeOC_(6)H_(2))N=CMe}-6-(ArN=CMe)C_5 H_(3)N]CoCl_(2)(Ar=2,6-Me_(2)C_(6)H_(3)Co1,2,6-Et_(2)C_(6)H_(3)Co2,2,6-iPr_(2)C_(6)H_(3)Co3,2,4,6-Me_(3)C_(6)H_(2)Co4,2,6-Et_(2)-4-MeC_(6)H_(2)Co5),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 by^(1)H-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(6.92×10^(6)g_(PE)·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=6.29×10^(5)g·mol^(-1)).All the polymers displayed high linearity as demonstrated by their melting temperatures(>130℃)and their~1 H-and^(13)C-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.
文摘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.
基金carried out according to the program of Fundamental Scientific Research of the Russian Federation
文摘The article describes ethylene polymerization reactions with transition metal catalysts based on complexes of CoCl_(2) and FeCl_(2) with an N,N,N-tridentate ligand 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine. The complexes are converted into polymerization catalysts by reacting them either with polymethylalumoxane (MAO) or with a combination of Al(C2H5)2Cl and Mg(C4H9)2 at an [Al]:[Mg] ratio of ~3. Both MAO-activated complexes readily polymerize ethylene at 35 ℃ with the formation of linear, low molecular weight polymers with a narrow molecular weight distribution. The same complexes, when activated with the Al(C2H5)2Cl-Mg(C4H9)2 combination, form multi-center catalysts and generate polyethylenes with a broad molecular weight distribution.
基金supported by National Natural Science Foundation of China(No.52203016)China Postdoctoral Science Foundation(Nos.2021M703072 and 2022T150617)+1 种基金USTC Research Funds of the Double First-Class Initiative(No.YD9990002018)The Fundamental Research Funds for the Central Universities(No.WK9990000142)。
文摘The external stimulus response strategy has been evolved rapidly in the field of olefin polymerization.In this work,we modularly synthesized three types of double stimulus responsiveα-diimine palladium catalysts,combining redox regulation and other regulation together,such as light,Lewis acid and alkali cations.The catalytic activities and the molecular weight of polyethylene products can be regulated for 4 times in ethylene polymerization.These palladium complexes were also used for the copolymerization reaction of ethylene and polar monomers,such as methyl 10-undecylenate and methyl acrylate,effectively regulating the catalytic activities,the molecular weight and polar monomer incorporation of the prepared copolymers.The research on these dual-regulated palladium complexes makes full use of prepared catalysts and provides new inspirations for regulating olefin polymerization.
基金Chinese Academy of Sciences for a President's International Fellowship for Visiting Scientists。
文摘The N,N,N'-ferrous chloride complexes,[2-{CMeN(2,4-(CHPh)_(2)-6-FC_(6)H_(2))}-6-(CMeNAr)C_(5)H_(3)N]FeCl_(2)(Ar=2,6-Me_(2)C_(6)H_(3) Fe1,2,6-Et_(2)C_(6)H_(3)Fe2,2,6-^(i)Pr_(2)C_(6)H_(3) Fe3,2,4,6-Me_(3)C_(6)H_(2) Fe4 and 2,6-Et_(2)-4-MeC_(6)H_(2) Fe5),each possessing one N-2,4-dibenzhydryl-6-fluorophenyl group,were readily synthesized from their respective unsymmetrical bis(imino)pyridines,L1-L5.Structural identification of Fe2 highlighted the variation in the steric properties provided by the dissimilar N-aryl groups.Following pre-treatment with either MAO or MMAO,complexes Fe1-Fe5 all displayed,at an operating temperature of 80℃,high activities for ethylene polymerization with levels falling in the order:Fe4> Fe1> Fe5> Fe2> Fe3.Notably,Fe4/MAO displayed the highest activity of 1.94×10^(7) g_(PE)·mol_(Fe)^(-1)·h^(-1) of the study with only a modest loss in performance at 90℃.Generally,the resulting polyethylenes were highly linear(T_(m) range:122-132℃),narrowly disperse and of low molecular weight(M_(w) range:6.73-46.04kg·mol^(-1)),with the most sterically hindered Fe3 forming the highest molecular weight polymer of the series.End-group analysis by ^(1)H-and ^(13)CNMR spectroscopy revealed saturated alkyl(n-propyl and i-propyl) and unsaturated vinyl chain ends indicative of the role of both β-H elimination and chain transfer to aluminum as termination pathways.By comparison with previou sly reported iron precatalysts with similar tridentate ligand skeletons,it is evident that the introduction of a large benzhydryl group in combination with a fluorine as the ortho-substituents of one N-aryl group has the effect of enhancing thermal stability of the iron polymerization catalyst whilst maintaining appreciable polymer molecular weight.
基金financially supported by the National Natural Science Foundation of China(Nos.20936006 and 20976152)National Basic Research Program of China(2011CB606001)+1 种基金Doctoral Program of Higher Education of China(No.20100101110041)Program for Changjiang Scholars and Innovative Research Team in Zhejiang University
文摘This contribution reports ethylene polymerization behavior of titanium complexes incorporating bis（phenoxyimine） ligands. Six phenoxy-imine Ti（IV） complexes {6-R^1-2-[CH=N（2,6-difluoro-3,5-diR^2-4-R^3Ph）]C6H30}2TiCl2 （1： R^1 = H, R^2 = H, R^3 = H; 2： R^1 = H, R^2 = H, R%3 = 4-vinylphenyl; 3： R^1 = CH3, R^2 = H, R^3 = H; 4： R^1 = CH3, R^2 = H, R^3 = 4-vinylphenyl; 5： R^1 = CH3, R^2 = F, R^3 = H; 6： R^1 = CH3, R^2 = F, R^3 = 4-vinylphenyl） have been synthesized and evaluated for ethylene polymerization using dried MAO （simplified as DMAO） as cocatalyst. An obvious catalytic heterogeneity of Cat 2 （Complex 2/DMAO） towards ethylene polymerization was observed, which was illustrated by decreased activity, multi- modal molecular weight distribution and partially improved particle morphology comparing with Cat 1. Moreover, Cat 3 exhibits ＂living＂ characteristics in the process under certain conditions （25 ~C, less than 20 min）. Otherwise, the moderate to high ethylene polymerization activity of ca. 105-106 g PE/（mol Ti＇h） and high molecular weight （Mw = 105-106） of polyethylene can be obtained by changing the skeleton structure of these complexes.
