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Methylaluminoxane
Kinds of Methylaluminoxane Selected AbstractsEthene Polymerization Behavior of MAO-Activated Dichloridotitanium Complexes Bearing Bi- and Tetradentate Salicylaldimine DerivativesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2010Antti Pärssinen Abstract New chiral bridged tetradentate (N2O2)TiIVCl2 -type complexes bearing dimethylbiphenyl (1-Ti,3-Ti) and previously published binaphthyl-bridged (4-Ti) complex were synthesized with high yields. This was achieved by treating the corresponding Schiff-base ligand (H2L) precursors with Ti(NMe2)4, followed by conversion of these diamido complexes to LTiCl2 derivatives by the addition of excess of Me3SiCl. A series of unbridged titanium complexes 5-Ti,8-Ti with similar substituents at the phenoxy group were studied and their polymerization properties, after methylaluminoxane (MAO) activation, compared with the above bridged complexes. It was found that the catalysts bearing chiral tetradentate biaryl-bridged salicylaldimine ligands produce multimodal polyethylene (PE) with low activity [below 10 kgPE/(molTi,h,bar)] while their unbridged analogues provide activities that are 10,1000 times greater under similar reaction conditions. The reasons for this dramatic difference in polymerization activities are discussed based on the stabilities of the different cationic species configurations. [source] Monocyclopentadienyl Phenoxido,Amino and Phenoxido,Amido Titanium Complexes: Synthesis, Characterisation, and Reactivity of Asymmetric Metal Centre DerivativesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2008Giuseppe Alesso Abstract Reduction of phenol,imine derivatives R,N=CH(3,5-R2C6H2 -2-OH) (R = tBu; R, = C6H51a, p -MeC6H41b, Cy 1c, tBu 1d, 2,6-Me2C6H31e; R = H; R, = p -MeC6H41f; Cy = cyclohexyl) with MBH4 (M = Li, Na) or AlLiH4 in ethyl ether or thf at room temperature affords the phenol,amine compounds R,NHCH2(3,5-R2C6H2 -2-OH) 2a,c and 2e,f. The N -R-[2,4-di- tert -butyl]benzo-1-oxa-3-azine species (R = tBu 2d1, 2,6-Me2C6H32e1) are obtained by Mannich reaction of 2,4-di- tert -butylphenol with RNH2 in refluxing methanol. Intermediate 2d1 is converted in ethanol at room temperature into N - tert -butyl[2-hydroxy-3,5-di- tert -butyl]benzylamine (2d), whereas 2e is not obtained from 2e1 by using this procedure.N -alkyl,N - tert -butyl[2-hydroxy-3,5-di- tert -butyl]benzylaminecompounds tBuN(R)CH2(3,5- tBu2C6H2 -2-OH) (R = Me 2g, Et 2h, nPr 2i, CH2Ph 2j) are also prepared by the appropriate synthetic method. Treatment of 2a,c with 1 equiv. of TiCpCl3 in the presence of 2.5 equiv. of NEt3 in hexane at room temperature gives the monocyclopentadienyl phenoxido,amido monochloride complexes TiCp[R,NCH2(3,5- tBu2C6H2 -2-O)]Cl (R, = C6H53a, R, = p -MeC6H43b, R, = Cy 3c). The analogous complex Ti(,5 -C5H4SiMe2Cl)[C6H5NCH2(3,5- tBu2C6H2 -2-O)]Cl (4a) results from the reaction of 2a with Ti(,5 -C5H4SiMe2Cl)Cl3. Nevertheless, 2d reacts with TiCpCl3 in hexane in the presence of NEt3 at room temperature yielding the monocyclopentadienyl phenoxido dichloride compound TiCp[tBuNHCH2(3,5- tBu2C6H2 -2-O)]Cl2 (5), whereas in ethyl ether and in the absence of NEt3 adduct 5·HCl is obtained, which is further converted into TiCp[tBuNCH2(3,5- tBu2C6H2 -2-O)]Cl (3d) by addition of a NEt3/ethyl ether solution. The reaction of TiCpCl3 with 2a in the presence of 2.5 equiv. of NEt3 in a polar solvent (thf, CH2Cl2 or toluene) at room temperature affords TiCp[Ph(H)NCH2(3,5- tBu2C6H2 -2-O)]Cl (6a) as a mixture of two stereoisomers. All the reported compounds were characterised by the usual analytical and spectroscopic methods and the molecular structures of 2a, 2d, 2e and 3d were determined by X-ray diffraction analysis from suitable single crystals. Preliminary studies of catalytic activity for ethylene polymerisation by using solid methylaluminoxane as cocatalyst were performed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Nickel Complexes and Cobalt Coordination Polymers with Organochalcogen (S, Se) Ligands Bearing an N -Methylimidazole Moiety: Syntheses, Structures, and Properties,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2008Wei-Guo Jia Abstract The organochalcogen ligands (S, Se) derived from 3-methylimidazole-2-thione/selone groups mbit (2a), mbis (2b), ebit (2c), and ebis (2d) [mbit = 1,1,-methylenebis(1,3-dihydro-3-methyl-2H -imidazole-2-thione), mbis = 1,1,-methylenebis(1,3-dihydro-3-methyl-2H -imidazole-2-selone), ebit = 1,1,-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H -imidazole-2-thione), ebis = 1,1,-(1,2-ethanediyl)bis(1,3-dihydro-3-methyl-1H -imidazole-2-selone)] were synthesized and characterized. Mononuclear NiII complexes NiBr2mbit (3a), NiBr2mbis (3b), NiBr2ebit (3c), and NiBr2ebis (3d) were obtained by the reactions of Ni(PPh3)2Br2 with 2a, 2b, 2c, and 2d, respectively. However, when the corresponding ligands 2a, 2b, 2c, and 2d were treated with CoCl2 in thf solution CoII 1D coordination polymers (CoCl2mbit)n (4a), (CoCl2mbis)n (4b), (CoCl2ebit)n (4c), and (CoCl2ebis)n (4d) were obtained. All compounds were fully characterized by IR spectroscopy and elemental analysis. The crystal structures of 2c, 3a, 3b, 3c, 4a, 4b, and 4c were determined by X-ray crystallography. The local geometry around the nickel atom in complexes 3a,c was distorted tetrahedron with coordinated S(Se) and two Br atoms, and the organochalcogen ligands form an eight- or a nine-membered ring with the nickel atom included. The cobalt atom coordination polymers 4a and 4b coexist as left-handed and right-handed helical chains, but 4c formed a zigzag chain with a CH3CN solvent molecule taken up in the channel structure. After activation with methylaluminoxane (MAO), the nickel complexes exhibited high activities for addition polymerization of norbornene (1.42,×,108 g,PNBmol,1,Nih,1 for 3a). The effects of the Al/Ni ratio, reaction temperature, and reaction time to norbornene polymerization were also investigated.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Sterically Demanding Iminopyridine LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 26 2007Torsten Irrgang Abstract Two sterically demanding iminopyridine ligands, (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridin-2-ylmethylene]amine and (2,6-diisopropylphenyl)[6-(2,6-dimethylphenyl)pyridin-2-ylmethylene]amine, were prepared by a two-step process: first, condensation of 6-bromopyridine-2-carbaldehyde with an equimolecular amount of 2,6-diisopropylaniline, and second, Kumada-type coupling of in-situ-formed Grignard compounds of 1-bromo-2,6-dimethylphenyl and 1-bromo-2,4,6-triisopropylphenyl. Dichlorido complexes of the ligands were synthesized starting from FeCl2, [PdCl2(cod)], [NiCl2(dme)], and CoCl2 (cod = 1,5-cyclooctadiene, dme = dimethoxyethane). X-ray crystal structure analyses of a Fe, Pd, and Co complex were determined. Ethylene polymerization/oligomerization behavior of the dichlorido complexes after activation with methylaluminoxane or triethylaluminum was studied. Ethylene dimerization selectivity greater than 95,% was observed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Studies of the Nature of the Catalytic Species in the ,-Olefin Polymerisation Processes Generated by the Reaction of Diamido(cyclopentadienyl)titanium Complexes with Aluminium Reagents as CocatalystsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2005Vanessa Tabernero Abstract The reaction of the diamido(chloro)cyclopentadienyltitanium compounds TiCpRx[1,2-C6H4(NR,)2]Cl [CpRx = ,5 -C5H5, ,5 -C5(CH3)5, ,5 -C5H4(SiMe3); R, = CH2tBu, Pr] with the Grignard reagent MgClR (R = Me, CH2Ph) affords the monomethyl and monobenzyl derivatives TiCpRx[1,2-C6H4(NR,)2]R. Upon addition of methylaluminoxane (MAO), the chloro- and alkyltitanium complexes show low activity towards the polymerisation of ethylene and styrene. However, no methylation was observed during the treatment of trimethylaluminium with the chloro compounds TiCpRx[1,2-C6H4(NR,)2]Cl. Instead, these reactions give the dinuclear aluminium complexes Al2[1,2-C6H4(NR,)2]Me4 (R, = CH2tBu, Pr) through transmetallation of the diamido ligand, suggesting a deactivation process of the catalysts in the olefin polymerisation reactions. In an additional effort to model the catalytic species, stoichiometric reactions between the methyl derivatives TiCpRx[1,2-C6H4(NR,)2]Me and solid methylaluminoxane (MAO) were studied by NMR spectroscopy. Monitoring of these reactions revealed the formation of zwitterionic species depending on the nature of the solvent. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Catalytic synthesis of styryl-capped isotactic polypropylenesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2010Huahua Huang Abstract Bis-styrenic molecules, 1,4-divinylbenzene (DVB) and 1,2-bis(4-vinylphenyl)ethane (BVPE), were successfully combined with hydrogen (H2) to form consecutive chain transfer complexes in propylene polymerization mediated by an isospecific metallocene catalyst (i.e., rac -dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride, I) activated with methylaluminoxane (MAO), rendering a catalytic access to styryl-capped isotactic polypropylenes (i -PP). The chain transfer reaction took place in a unique way where prior to the ultimate chain transfer DVB/H2 or BVPE/H2 caused a copolymerization-like reaction leading to the formation of main chain benzene rings. A preemptive polymer chain reinsertion was deduced after the consecutive actions of DVB/H2 or BVPE/H2, which gave the styryl-terminated polymer chain alongside a metal-hydride active species. It was confirmed that the chain reinsertion occurred in a regio-irregular 1,2-fashion, which contrasted with a normal 2,1-insertion of styrene monomer and ensured subsequent continuous propylene insertions, directing the polymerization to repeated DVB or BVPE incorporations inside polymer chain. Only as a competitive reaction, the insertion of propylene into metal-hydride site broke the chain propagation resumption process while completed the chain transfer process by releasing the styryl-terminated polymer chain. BVPE was found with much higher chain transfer efficiency than DVB, which was attributed to its non-conjugated structure with much divided styrene moieties resulting in higher polymerization reactivity but lower chain reinsertion tendency. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3709,3713, 2010 [source] Controlled vinyl-type polymerization of norbornene with a Nickel(II) diphosphinoamine/methylaluminoxane catalytic systemJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2009Georgios C. Vougioukalakis Abstract A novel nickel-based complex coordinated with an asymmetric diphosphinoamine ligand was synthesized and fully characterized. Single crystals of good quality were also obtained, and the solid-state structure of the complex was studied via X-rays diffraction. The catalytic activity of this Ni(II) complex in the vinyl-type polymerization of norbornene was studied with methylaluminoxane (MAO) as the cocatalyst/activator. The influence of the reaction time, the equivalents of MAO used, and the concentration of the monomer on: (i) the activity of the catalytic system; (ii) the isolated yield of the polymer; and (iii) the molecular weight and molecular weight distribution of the polymer were investigated. The isolated polynorbornene (PNB) yields are significantly higher compared with those reported for other similar nickel-based systems. The as-obtained PNBs are characterized by high molecular weights and relatively narrow and monomodal molecular weight distributions (amongst the narrowest reported in the literature). The linear dependence of the molecular weight of the obtained PNB on the concentration of norbornene points toward a controlled polymerization reaction. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5241,5250, 2009 [source] Synthesis of a new zirconium catalyst for ethylene polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2008Fabiana De C. Fim Abstract A novel complex dichlorobis(2-ethyl-3-hydroxy-4-pyrone)zirconium(IV) (ZrCl2(ethylpyrone)2) was synthesized. Complexation of the pyrone ligand to the zirconium was confirmed by UV, 1H and 13C-NMR, and electrochemical studies. NMR showed the presence of four isomers and density functional theory calculations indicated that the main isomer had a cis configuration. The catalyst was shown to be active in ethylene polymerization in the presence of the cocatalyst methylaluminoxane. The highest catalyst activity for the zirconium complex was achieved at Al/Zr = 2500, 70 °C and when a small concentration of catalyst was used (1 ,mol). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3830,3841, 2008 [source] Vinyl polymerization of norbornene by mono- and trinuclear nickel complexes with indanimine ligandsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2008Guangrong Tang Abstract A series of new indanimine ligands [ArNCC2H3(CH3)C6H2(R)OH] (Ar = Ph, R = Me (1), R = H (2), and R = Cl (3); Ar = 2,6- i -Pr2C6H3, R = Me (4), R = H (5), and R = Cl (6)) were synthesized and characterized. Reaction of indanimines with Ni(OAc)2·4H2O results in the formation of the trinuclear hexa(indaniminato)tri (nickel(II)) complexes Ni3[ArN = CC2H3(CH3)C6H2(R)O]6 (Ar = Ph, R = Me (7), R = H (8), and R = Cl (9)) and the mononuclear bis(indaniminato)nickel (II) complexes Ni[ArNCC2H3(CH3)C6H2(R)O]2 (Ar = 2,6- i -Pr2C6H3, R = Me (10), R = H (11), and R = Cl (12)). All nickel complexes were characterized by their IR, NMR spectra, and elemental analyses. In addition, X-ray structure analyses were performed for complexes 7, 10, 11, and 12. After being activated with methylaluminoxane (MAO), these nickel(II) complexes can polymerize norbornene to produce addition-type polynorbornene (PNB) with high molecular weight Mv (106 g mol,1), highly catalytic activities up to 2.18 × 107 gPNB mol,1 Ni h,1. Catalytic activities and the molecular weight of PNB have been investigated for various reaction conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 489,500, 2008 [source] Homo- and copolymerization of ethylene and norbornene with bis(,-diketiminato) titanium complexes activated with methylaluminoxaneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2008Yongfei Li Abstract Homo- and copolymerization of ethylene and norbornene were investigated with bis(,-diketiminato) titanium complexes [ArNC(CR3)CHC(CR3)NAr]2TiCl2 (R = F, Ar = 2,6-diisopropylphenyl 2a; R = F, Ar = 2,6-dimethylphenyl 2b; R = H, Ar = 2,6-diisopropylphenyl 2c; R = H, Ar = 2,6-dimethylphenyl 2d) in the presence of methylaluminoxane (MAO). The influence of steric and electric effects of complexes on catalytic activity was evaluated. With MAO as cocatalyst, complexes 2a,d are moderately active catalysts for ethylene polymerization producing high-molecular weight polyethylenes bearing linear structures, but low active catalysts for norbornene polymerization. Moreover, 2a,d are also active ethylene,norbornene (E,N) copolymerization catalysts. The incorporation of norbornene in the E,N copolymer could be controlled by varying the charged norbornene. 13C NMR analyses showed the microstructures of the E,N copolymers were predominantly alternated and isolated norbornene units in copolymer, dyad, and triad sequences of norbornene were detected in the E,N copolymers with high incorporated content of norbornene. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 93,101, 2008 [source] Polymerization of ,-pinene with Schiff-base nickel complexes catalyst: Synthesis of relatively high molecular weight poly(,-pinene) at high temperature with high productivityJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2007Peng Yu Abstract A series of easily accessible and stable Schiff-base nickel complexes (complex 1,4) in conjunction with methylaluminoxane (MAO) were employed for the synthesis of relatively high molecular weight ,-pinene polymers at high temperature with high productivity. The ligand structure of the complex had a substantial effect on the polymerization in terms of the productivity and the molecular weight. With complex 4 in the presence of MAO, high molecular weight polymers of ,-pinene (Mn , 10,900) were obtained at 40 °C with an extremely high productivity up to 1.25 × 107 g poly,-pinene/mol of Ni. 1H NMR analyses showed that the obtained ,-pinene polymer was structurally identical to that formed by conventional cationic Lewis acid initiators. The polymerization was presumably initiated by the nickel cation formed by the reaction of the schiff-base nickel complex and MAO, while the propagation proceeded in a manner typical for a conventional carbocationic polymerization process. Direct evidence for the carbocationic polymerization was offered by the fact that quenching of the polymerization with methanol at a low monomer conversion resulted in incorporation of a methoxyl end group into the polymer chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3739,3746, 2007 [source] Bis(salicylaldiminate)copper(II)/methylaluminoxane catalysts for homo- and copolymerizations of ethylene and methyl methacrylateJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2007Anna Maria Raspolli Galletti Abstract Bis(salicylaldiminate)copper(II) complexes, when activated with methylaluminoxane, catalyzed the homo- and copolymerizations of ethylene and methyl methacrylate (MMA). The activity in the MMA homopolymerization was influenced by the electronic and steric characteristics of the Cu(II) precursors as well as the cocatalyst concentration. The same systems revealed modest activity also in the homopolymerization of ethylene, giving a highly linear polyethylene, and in its copolymerization with MMA. These copolymers exhibited a very high content of polar groups (MMA units > 70 mol %) and were characterized by a high molecular weight and polydispersity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1134,1142, 2007 [source] Copolymerization of norbornene and styrene catalyzed by a novel anilido,imino nickel complex/methylaluminoxane systemJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2006Haiyang Gao Abstract Copolymerizations of norbornene with styrene were carried out with a catalytic system of anilido,imino nickel complex (ArNCHC6H4NAr)NiBr (Ar = 2,6-dimethylphenyl) and methylaluminoxane in toluene. The influence of the comonomer feed content and polymerization temperature on the conversion and composition of the copolymers with (ArNCHC6H4NAr)NiBr/methylaluminoxane was investigated. An increase in the initial styrene feed content led to an increase in the incorporated styrene content of the resulting copolymer. The determination of the reactivity ratios showed a much high reactivity for norbornene (reactivity ratio for styrene = 0.26, reactivity ratio for norbornene = 20.78), which was consistent with a coordination mechanism. NMR analysis of the end groups further confirmed that the chain was initiated through a styrene secondary insertion or a norbornene insertion into NiH and terminated through ,-H elimination from an inserted styrene unit. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5237,5246, 2006 [source] Copolymerization of ethylene with styrene catalyzed by a linked bis(phenolato) titanium catalystJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2006Carmine Capacchione Abstract Copolymerization of ethylene with styrene, catalyzed by 1,4-dithiabutanediyl-linked bis(phenolato) titanium complex and methylaluminoxane, produced exclusively ethylene,styrene copolymers with high activity. Copolymerization parameters were calculated to be rE = 1.2 for ethylene and rS = 0.031 for styrene, with rErS = 0.037 indicating preference for alternating copolymerization. The copolymer microstructure can be varied by changing the ratio between the monomers in the copolymerization feed, affording copolymers with styrene content up to 68%. The copolymer microstructure was fully elucidated by 13C NMR spectroscopy revealing, in the copolymers with styrene content higher than 50%, the presence of long styrene,styrene homosequences, occasionally interrupted by isolated ethylene units. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1908,1913, 2006 [source] Preparation of linear ,-olefins to high-molecular weight polyethylenes using cationic ,-diimine nickel(II) complexes containing chloro-substituted ligands,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2006Chun-Lei Song Abstract A series of ,-diimine nickel(II) complexes containing chloro-substituted ligands, [(Ar)NC(C10H6)CN(Ar)]NiBr2 (4a, Ar = 2,3-C6H3Cl2; 4b, Ar = 2,4-C6H3Cl2; 4c, Ar = 2,5-C6H3Cl2; 4d, Ar = 2,6-C6H3Cl2; 4e, Ar = 2,4,6-C6H2Cl3) and [(Ar)NC(C10H6)CN(Ar)]2NiBr2 (5a, Ar = 2,3-C6H3Cl2; 5b, Ar = 2,4-C6H3Cl2; 5c, Ar = 2,5-C6H3Cl2), have been synthesized and investigated as precatalysts for ethylene polymerization. In the presence of modified methylaluminoxane (MMAO) as a cocatalyst, these complexes are highly effective catalysts for the oligomerization or polymerization of ethylene under mild conditions. The catalyst activity and the properties of the products were strongly affected by the aryl-substituents of the ligands used. Depending on the catalyst structure, it is possible to obtain the products ranging from linear ,-olefins to high-molecular weight polyethylenes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1964,1974, 2006 [source] Vinyl polymerization of norbornene by bis(nitro-substituted-salicylaldiminate)nickel(II)/methylaluminoxane catalystsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2006Carlo Carlini Abstract The polymerization of norbornene has been investigated in the presence of different bis(salicylaldiminate)nickel(II) precursors activated by methylaluminoxane. These systems are highly active in affording nonstereoregular vinyl-type polynorbornenes (PNBs) with high molecular weights. The productivity of the catalytic systems is strongly enhanced (up to 35,000 kg of PNB/mol of Ni × h) when electron-withdrawing nitro groups are introduced on the phenol moiety. On the contrary, the presence of bulky alkyl groups on the N -aryl moiety of the ligand does not substantially affect the activity or characteristics of the resulting PNBs. The catalytic performances are also markedly influenced by the reaction parameters, such as the nature of the solvent, the reaction time, and the monomer/Ni and Al/Ni molar ratios. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1514,1521, 2006 [source] Propylene polymerization with nickel,diimine complexes containing pseudohalidesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2006Marcos L. Dias Abstract DADNiX2 nickel,diimine complexes [DAD = 2,6- iPr2C6H3NC(Me)C(Me)N2,6- iPr2C6H3] containing nonchelating pseudohalide ligands [X = isothiocyanate (NCS) for complex 1 and isoselenocyanate (NCSe) for complex 2] were synthesized, and the propylene polymerization with these complexes and also with the Br ligand (X = Br for complex 3) activated by methylaluminoxane (MAO) were investigated (systems 1, 2, and 3/MAO). The polypropylenes obtained with systems 1, 2, and 3 were amorphous polymers and had high molecular weights and narrow molecular weight distributions. Catalyst system 1 showed a relatively high activity even at a low Al/Ni ratio and reached the maximum activity at the molar ratio of Al/Ni = 500, unlike system 3. Increases in the reaction temperature and propylene pressure favored an increase in the catalytic activity. The spectra of polypropylenes looked like those of propylene,ethylene copolymers containing syndiotactic propylene and ethylene sequences. At the same temperature and pressure, system 2 presented the highest number of propylene sequences, and system 3 presented the lowest. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 458,466, 2006 [source] Ethylene/,-olefin copolymerization with bis(,-enaminoketonato) titanium complexes activated with modified methylaluminoxaneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2005Li-Ming Tang Abstract Copolymerizations of ethylene with ,-olefins (i.e., 1-hexene, 1-octene, allylbenzene, and 4-phenyl-1-butene) using the bis(,-enaminoketonato) titanium complexes [(Ph)NC(R2)CHC(R1)O]2TiCl2 (1a: R1 = CF3, R2 = CH3; 1b: R1 = Ph, R2 = CF3; and 1c: R1 = t -Bu, R2 = CF3), activated with modified methylaluminoxane as a cocatalyst, have been investigated. The catalyst activity, comonomer incorporation, and molecular weight, and molecular weight distribution of the polymers produced can be controlled over a wide range by the variation of the catalyst structure, ,-olefin, and reaction parameters such as the comonomer feed concentration. The substituents R1 and R2 of the ligands affect considerably both the catalyst activity and comonomer incorporation. Precatalyst 1a exhibits high catalytic activity and produces high-molecular-weight copolymers with high ,-olefin insertion. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6323,6330, 2005 [source] Highly active copolymerization of ethylene with 10-undecen-1-ol using phenoxy-based zirconium/methylaluminoxane catalystsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2005Xiaofan Zhang Abstract Activated with methylaluminoxane (MAO), phenoxy-based zirconium complexes bis[(3- tBu-C6H3 -2-O)-CHNC6H5]ZrCl2, bis[(3,5-di- tBu-C6H2 -2-O)-PhCNC6H5] ZrCl2, and bis[(3,5-di- tBu-C6H2 -2-O)-PhCN(2-F-C6H4)]ZrCl2 for the first time have been used for the copolymerization of ethylene with 10-undecen-1-ol. In comparison with the conventional metallocene, the phenoxy-based zirconium complexes exhibit much higher catalytic activities [>107 g of polymer (mol of catalyst),1 h,1]. The incorporation of 10-undecen-1-ol into the copolymers and the properties of the copolymers are strongly affected by the catalyst structure. Among the three catalysts, complex c is the most favorable for preparing higher molecular weight functionalized polyethylene containing a higher content of hydroxyl groups. Studies on the polymerization conditions indicate that the incorporated commoner content in the copolymers mainly depends on the comonomer concentration in the feed. The catalytic activity is slightly affected by the Al(MAO)/Zr molar ratio but decreases greatly with an increase in the polymerization temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5944,5952, 2005 [source] Vinylic and ring-opening metathesis polymerization of norbornene with bis(,-ketoamine) cobalt complexes,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2005Feng Bao Abstract Cobalt complexes 1,4 bearing N,O -chelate ligands based on condensation products of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone with aniline, o -methylaniline, ,-naphthylamine, and p -nitroaniline, respectively, were synthesized, and the structures of 1 and 4 were characterized by single-crystal X-ray diffraction analyses. The bis(,-ketoamine) cobalt complexes could act as moderately active catalyst precursors for norbornene polymerization with the activation of methylaluminoxane. This catalytic reaction proceeded mainly through a vinyl-type polymerization mechanism. 1H NMR and IR showed that in all cases, a small amount of double bonds raised from ring-opening metathesis polymerization (ROMP) was present in the polymerization products. The variation of the polymerization conditions affected the ROMP unit ratio in the polynorbornenes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5535,5544, 2005 [source] Effects of methylaluminoxane immobilization on silica on the performance of zirconocene catalysts in propylene polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2005Madri Smit Abstract Investigation of the characteristics and performance in propylene polymerization of silica-immobilized methylaluminoxane (MAO), in combination with a moderately and a highly isospecific zirconocene catalyst, has revealed that a simple impregnation of silica with MAO at ambient temperature is insufficient to obtain uniform distribution of MAO throughout the support particle. Homogeneous Al distribution throughout the support, giving increased catalyst activity, was achieved by a more rigorous impregnation of silica with MAO at elevated temperatures. The highest catalyst activities were obtained by precontacting the MAO with the zirconocene to generate the activated species before immobilization on silica. Polymer particle morphology was strongly dependent on the characteristics of the silica used for catalyst immobilization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2734-2748, 2005 [source] The discovery of metallocene catalysts and their present state of the artJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2004Walter Kaminsky Abstract Metallocene and other transition metal complexes activated by methylaluminoxane are highly active catalysts for the polymerization of olefins, diolefins, and styrene, which was discovered at the University of Hamburg about 25 years ago. These catalysts allow the synthesis of polymers with a highly defined microstructure, tacticity, and stereoregularity, as well as new copolymers with superior properties such as film clarity, tensile strength, and lower extractables. A better understanding of the mechanism of olefin polymerization leads to findings of other new single site catalysts. The development of the metallocene/MAO-catalysts from their discovery to their present state of the art is presented. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3911,3921, 2004 [source] 13C NMR determination of the microstructure of polypropylene obtained with the DADNi(NCS)2/methylaluminoxane catalyst systemJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2004Griselda Barrera Galland Abstract A complete 13C NMR characterization of a polymer synthesized with a new Ni-diimine complex [DADNi(NCS)2, where DAD = 2,6 - iPrC6H3NC(Me)C(Me) N2,6 - iPrC6H3] activated by methylaluminoxane by homopolymerization of propylene is presented. The amorphous material was made up mainly of blocks of syndiotactic polypropylene and ethylene,propylene copolymer. Some degree of propylene inversion (<1.2 mol %) and of long isobutyl and 2-methyl hexyl branching (<1 mol %) were assigned and quantified. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2171,2178, 2004 [source] In situ ethylene homopolymerization and copolymerization catalyzed by zirconocene catalysts entrapped inside functionalized montmorilloniteJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2003Chengbin Liu Abstract Ethylene homopolymerizations and copolymerizations were catalyzed by zirconocene catalysts entrapped inside functionalized montmorillonites that had been rendered organophilic via the ion exchange of the interlamellar cations of layered montmorillonite with hydrochlorides of L -amino acids (AAH+Cl,) or their methyl esters (MeAAH+Cl,), with or without the further addition of hexadecyltrimethylammonium bromide (C16H33N+Me3Br,; R4N+Br,). In contrast to the homogeneous Cp2ZrCl2/methylaluminoxane catalyst for ethylene homopolymerizations and copolymerizations with 1-octene, the intercalated Cp2ZrCl2 activated by methylaluminoxane for ethylene homopolymerizations and copolymerizations with 1-octene proved to be more effective in the synthesis of polyethylenes with controlled molecular weights, chemical compositions and structures, and properties, including the bulk density. The effects of the properties of the organic guests on the preparation and catalytic performance of the intercalated zirconocene catalysts were studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2187,2196, 2003 [source] Structure,property transition-state model for the copolymerization of ethene and 1-hexene with experimental and theoretical applications to novel disilylene-bridged zirconocenesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2003Hanne Wigum Abstract Ethene homopolymerization and copolymerization with 1-hexene were performed with three new tetramethyldisilylene-bridged zirconocene catalysts with 2-indenyl ligand (A), 2-tetrahydroindenyl ligand (B), and tetramethyl-cyclopentadienyl ligand (C) and with methylaluminoxane as a cocatalyst. Catalysts A and B showed substantial comonomer incorporation, resulting in a copolymer melting temperature more than 20° lower than that of the corresponding homopolymer. In contrast, catalyst C produced a copolymer with a low 1-hexene content and a high melting temperature. The reduction in the molecular weight with 1-hexene addition also correlated well with the comonomer incorporation. For all three catalysts, the homopolymer and copolymer unsaturations indicated frequent chain termination after 1-hexene insertion and a high degree of chain-end isomerization during the homopolymerization of ethene. The chain transfer to Al in the cocatalyst also appeared to be important. The comonomer response could be correlated with the structural properties of the catalyst, as derived from quantum chemical calculations. A linear model, calibrated against recent experiments with unbridged (MenC5H5,n)2ZrCl2 catalysts, suggested that the low comonomer incorporation obtained with catalyst C was caused partly by a narrow opening angle between the aromatic ligands and partly by steric hindrance in the transition state of comonomer insertion. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1622,1631, 2003 [source] Nickel(II) and palladium(II) complexes with ,-dioxime ligands as catalysts for the vinyl polymerization of norbornene in combination with methylaluminoxane, tris(pentafluorophenyl)borane, or triethylaluminum cocatalyst systems,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2002Bernd Berchtold Abstract Nickel(II) and palladium(II) complexes with ,-dioxime ligands dimethylglyoxime, diphenylglyoxime, and 1,2-cyclohexanedionedioxime represent six new precatalysts for the polymerization of norbornene that can be activated with methylaluminoxane (MAO), the organo-Lewis acid tris(pentafluorophenyl)borane [B(C6F5)3], and triethylaluminum (TEA) AlEt3. The palladium but not the nickel precatalysts could also be activated by B(C6F5)3 alone, whereas two of the three nickel precatalysts but none of the palladium systems are somewhat active with only TEA as a cocatalyst. It was possible to achieve very high polymerization activities up to 3.2 · 107 gpolymer/molmetal · h. With the system B(C6F5)3/AlEt3, the activation process can be formulated as the following two-step reaction: (1) B(C6F5)3 and TEA lead to an aryl/alkyl group exchange and result in the formation of Al(C6F5)nEt3,n and B(C6F5)3,nEtn; and (2) Al(C6F5)nEt3,n will then react with the precatalysts to form the active species for the polymerization of norbornene. Variation of the B:Al ratio shows that Al(C6F5)Et2 is sufficient for high activation. Gel permeation chromatography indicated that it was possible to control the molar mass of poly(norbornene)s by TEA or 1-dodecene as chain-transfer agents; the molar mass can be varied in the number-average molecular weight range from 2 · 103 to 9 · 105 g · mol,1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3604,3614, 2002 [source] Syndiospecific polymerization of styrene with BzCpTiCl3 and methylaluminoxane as cocatalystsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2001Constantin Schwecke Abstract Benzyl cyclopentadienyl titanium trichloride (BzCpTiCl3) was synthesized from benzyl bromide, cyclopentadienyl lithium, and titanium tetrachloride and used in combination with methylaluminoxane (MAO) for the syndiospecific polymerization of styrene. Kinetic measurements of the polymerization were carried out at different temperatures. The polymerization with BzCpTiCl3/MAO differs from the polymerization with cyclopentadienyl titanium trichloride in its behavior toward the Al/Ti ratio. In addition, high activities are observed at high Al/Ti ratios. By analyzing the polymerization runs and the physical properties of the polymers with differential scanning calorimetry, 13C NMR spectroscopy, wide-angle X-ray scattering measurements, and gel permeation chromatography, we found that the phenyl ring coordinates to the titanium atom during polymerization. Other known substitutions of the cyclopentadienyl ring (V. Scholz, Dissertation, University of Hamburg, 1998) in principle influence the polymerization activity. The physical properties of the polymers produced by the catalysts already known are nearly identical. BzCpTiCl3 is the first catalyst that leads to polystyrene obviously different from the polystyrene produced by other highly active catalysts. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2805,2812, 2001 [source] Syndiospecific polymerization of styrene catalyzed by CpTiCl2(OR) complexesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2001Haiyan Ma Abstract Five new CpTiCl2(OR) alkoxyl-substituted half-sandwich complexes, where R was methoxyethyl (1), methoxypropyl (2), methoxyisopropyl (3), o -methoxyphenyl (4), or tetrahydrofurfuryl (5), were synthesized, characterized, and tested as catalyst precursors for the syndiospecific polymerization of styrene. These precursors were more active than (,5 -cyclopentadienyl)trichlorotitanium (CpTiCl3). The different structures of the alkoxyl ligands affected the activity slightly. When the polymerization was carried out in bulk, all the complexes (1,5) exhibited high activities, even at the low molar ratio of Al/Ti = 300. The syndiotactic polystyrene (s-PS) percentage of the polymer produced by alkoxyl-substituted complexes was much higher than that of CpTiCl3. The really active center might be described as [CpTiMe]+ · [MAOX], · nMAO (where MAO is methylaluminoxane). The normal active species [CpTiMe]+ made up the core and the anion mass [MAOX], · nMAO surrounded the core and constituted the outer shell circumstance. They activated the syndiospecific polymerization of styrene as a whole. For a high concentration of MAO, the function of the alkoxyl group was weak because of the limited proportion in the outer shell. For a low concentration of MAO, the proportion of alkoxyl ligands in the outer shell increased greatly, and their influence also became significant, as reflected in a higher s-PS percentage of the obtained polymer. The existence of the additional oxygen atom in the alkoxyl ligand stabilized the active species more effectively; this was reflected in the higher temperature of the maximum activities. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1817,1824, 2001 [source] Lanthanide Metal-Organic Frameworks as Ziegler,Natta Catalysts for the Selective Polymerization of IsopreneMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 22 2009Marta J. Vitorino Abstract The unprecedented ability of neodymium-based metal organic frameworks (MOFs) as polymerisation pre-catalysts towards isoprene is reported. Combined with methylaluminoxane (MAO) or modified MAO (MMAO), they afford mainly cis -selective polyisoprene, up to 90.7%. Both the activity and the selectivity are tentatively ascribed to the intrinsic microstructure of the starting materials. Compared to conventional carboxylates, MOFs associated to an Al co-catalyst are less active but the selectivity is found to be higher, and it may be modified by controlling the access to the pores, which would be favored at higher temperatures. Some residual crystalline MOF remains disseminated within the polymer matrix, as shown by X-ray diffraction and X-ray absorption spectroscopy studies. [source] Tandem Action of TpMsNiCl and Supported Cp2ZrCl2 Catalysts for the Production of Linear Low-Density PolyethyleneMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 9 2006Maria Cristina A. Kuhn Abstract Summary: Linear low-density polyethylene (LLDPE) samples with different properties were prepared from ethylene, without the addition of an , -olefin co-monomer, using a combination of the catalyst precursors TpMsNiCl (TpMs,=,hydridotris(3-mesitylpyrazol-1-yl) and Cp2ZrCl2/SMAO-4, by varying the nickel loading mole fraction (xNi). Upon activation with methylaluminoxane (MAO), this binary catalytic system showed activities varying from 12.3 to 309.1 kg of PE,·,(mol[M],·,atm,·,h),1. The properties of the polymeric materials are influenced by xNi as well as by the temperature of polymerization, affording the copolymers with a melting point (Tm) between 118 and 135,°C. The GPC results show that the molecular weight () of the polymers is sensitive to the xNi. In all of the cases studied, the GPC curves displayed monomodal molecular weight distributions (MWDs) with the average molecular weight varying from 30,000 to 507,000 g,·,mol,1. Studies using dynamic mechanical thermal analysis (DMTA) show that the formation of different polymeric materials is associated with the branching content, with the stiffness varying according to the xNi and the temperature used in the polymerization reaction. Overview of the copolymerization process, from ethylene in the presence of MAO, mediated by catalysts 1 and 2/SMAO. [source] | |||||||||||||