Stereospecific Polymerization Of Propylene Research Articles

Scandium‐Catalyzed Polymerization of CH3(CH2)nCH=CH2 (n = 0–4): Remarkable Activity and Tacticity Control

AbstractThe C3‐symmetric trisoxazoline‐supported scandium complex [Sc(iPr‐trisox)(CH2SiMe3)3] (2) is highly active in the stereospecific polymerization of propene, 1‐butene, 1‐pentene, 1‐hexene and 1‐heptene, when activated with two equivalents of [Ph3C][B(C6F5)4]. The polymers thus produced were found to possess narrow molecular weight distributions and high levels of tacticity control (up to 99 % mmmm). Some insight into the nature of the active species was obtained by 1H, 13C and 29Si NMR experiments. In particular, the formation of two equivalents of Ph3CCH2SiMe3 at ambient temperature was observed alongside a C3‐symmetric scandium complex tentatively assigned as the dication [Sc(iPr‐trisox)(CH2SiMe3)]2+.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Stereospecific polymerization of propylene with group 4 ansa-fluorenylamidodimethyl complexes

Group 4 [η 1:η 3- tert-butyl(dimethylfluorenylsilyl)amido]dimethyl complexes [ t-BuNSiMe 2Flu]MMe 2 (M = Ti, 1; Zr, 2; Hf, 3) were synthesized in a one-pot synthesis starting from the ligand, MeLi and MCl 4 (M = Ti, Zr, Hf), respectively. The structures of these complexes were determined by X-ray crystallography and the results obtained revealed that the fluorenyl ligand coordinates to center metal in a η 3-manner irrespective of center metal employed. Propylene polymerization was conducted at 0 or 20 °C in toluene by 1– 3 combined with dried methylaluminoxane (MAO), which was prepared from the toluene solutions of MAO by removing free trialkylaluminiums, and HNMe 2PhB(C 6F 5) 4 in the presence of triisobutylaluminium. The 1–dried MAO system gave the polymer with syndiotactic triad (rr) of 63% at 0 °C, whereas 2 and 3 did not give any polymer in the same conditions. The 2–dried MAO system gave the polymer with the highest syndiotacticity (rr = 97%) at 20 °C, although the activity was low. The 3–dried MAO system did not give any polymer even at 20 °C. When HNMe 2PhB(C 6F 5) 4 was used in place of dried MAO at 20 °C, 1 gave almost atactic polymer, while 2 and 3 gave highly syndiotactic one (rr > 90%). These results indicate that the catalytic performance strongly depended on the center metal of the ansa-fluorenylamidodimethyl complexes as well as cocatalysts employed.

Syndiospecific living propylene polymerization catalyzed by titanium complexes having fluorine-containing phenoxy-imine chelate ligands.

The propylene polymerization behavior of a series of Ti complexes featuring fluorine-containing phenoxy-imine chelate ligands is reported. The Ti complexes combined with methylalumoxane (MAO) can be catalysts for living and, at the same time, stereospecific polymerization of propylene at room temperature or above. DFT calculations suggest that the attractive interaction between a fluorine ortho to the imine nitrogen and a beta-hydrogen of a growing polymer chain is responsible for the achievement of room-temperature living propylene polymerization. Although the Ti complexes possess C(2) symmetry, they are capable of producing highly syndiotactic polypropylenes. (13)C NMR is used to demonstrate that the syndiotacticity is governed by a chain-end control mechanism and that the polymerization is initiated exclusively via 1,2-insertion followed by 2,1-insertion as the principal mode of polymerization. (13)C NMR spectroscopy also elucidated that the polypropylenes produced with the Ti complexes possess regio-block structures. Substitutions on the phenoxy-imine ligands have profound effects on catalytic behavior of the Ti complexes. The steric bulk of the substituent ortho to the phenoxy oxygen plays a decisive role in achieving high syndioselectivity for the chain-end controlled polymerization. Over a temperature range of 0-50 degrees C, Ti complex having a trimethylsilyl group ortho to the phenoxy oxygen forms highly syndiotactic, nearly monodisperse polypropylenes (94-90% rr) with extremely high peak melting temperatures (T(m) = 156-149 degrees C). The polymerization behavior of the Ti complexes can be explained well by the recently proposed site-inversion mechanism for the formation of syndiotactic polypropylene by a Ti complex having a pair of fluorine-containing phenoxy-imine ligands.

Chain transfer reaction by trialkylaluminum (AIR3) in the stereospecific polymerization of propylene with metallocene — AIR3/Ph3CB(C6F5)4

Stereospecific polymerization of propylene was carried out with rac-ethylenebis(indenyl)zirconium dichloride (rac-Et(Ind)2ZrCl2) (1), rac-dimethylsilylenebis(indenyl)zirconium dichloride (rac-Me2Si(Ind)2ZrCl2) (2) and isopropylidene(cyclopentadienyl)(9-fluorenyl)zirconium dichloride (i-Pr(Cp)(Flu)ZrCl2) (3) combined with trialkyl-aluminum (AIR3: R = C2H5, i-C4H9)/triphenylcarbenium tetrakis(pentafluorophenyl)borate (Ph3CB(C6F5)4) (4). In isospecific polymerization with 1 and 2, the molecular weight of polypropylenes decreased with increase in the molar ratio of AlEt3 (Et = C2H5)/Zr, whereas, an effect of AliBu3 (iBu = i-C4H9) concentration on molecular weight was not observed. The microstructures of resulting polypropylenes were studied by 13C n.m.r. and an increase in the molar ratio of ethyl end groups (derived from chain transfer to AlEt3) to n-propyl end groups (derived from β-hydrogen transfer) was observed with increase in the molar ratio of AlEt3Zr (1 and 2). The chain transfer reactions by both AlEt3 and AliBu3 were also detected in syndiospecific polymerization with 3. The molar ratio of alkyl (R) end groups (derived from chain transfer to AIR3) to n-propyl end groups was higher in the polypropylene obtained with AlEt3 than that obtained with AliBu3. The relative constants ktrAkp (ktrA = rate constant of chain transfer to AIR3, kp = rate constant of propagation) were determined by kinetic study.

Effect of polarity of the medium on the stereospecific polymerization of propylene by ansa‐zirconocene catalyst

AbstractPropylene was polymerized with rac‐ethylene‐bis (1‐η5‐indenyl)dichlorozirconium/methylaluminoxane in solvents of different polarity. The poly (propylene) formed was separated by solvent extraction; 13C‐NMR and DSC measurements were made on the polymer fractions. The poly(propylene) in each solvent fraction has its characteristic molecular weight steric pentad distributions, melting transition temperature, and enthalpy for fusion irrespective of the polymerization medium. The results suggest that the medium dielectric constant does not affect the polymerization rate or the intrinsic stereoselectivity, propagation and chain transfer rates a given catalytic species but can alter the occurrence of steric insertion errors through shifting of distributions of the propagating species producing poly(propylenes) of different stereoregularities. © 1994 John Wiley & Sons, Inc.

A novel MgCl2‐supported Ziegler‐Natta catalyst composition: Stereospecific polymerization of propene without external donor

Die Makromolekulare Chemie, Rapid CommunicationsVolume 14, Issue 2 p. 133-137 Article A novel MgCl2-supported Ziegler-Natta catalyst composition: Stereospecific polymerization of propene without external donor Eero Iiskola, Corresponding Author Eero Iiskola Neste Chemicals, P. O. Box 320, SF-06101 Porvoo, FinlandNeste Chemicals, P. O. Box 320, SF-06101 Porvoo, FinlandSearch for more papers by this authorAija Pelkonen, Aija Pelkonen Neste Chemicals, P. O. Box 320, SF-06101 Porvoo, FinlandSearch for more papers by this authorHeikki J. Kakkonen, Heikki J. Kakkonen University of Joensuu, Department of Chemistry, P. O. Box 111, SF-80101 Joensuu, FinlandSearch for more papers by this authorJouni Pursiainen, Jouni Pursiainen University of Joensuu, Department of Chemistry, P. O. Box 111, SF-80101 Joensuu, FinlandSearch for more papers by this authorTapani A. Pakkanen, Tapani A. Pakkanen University of Joensuu, Department of Chemistry, P. O. Box 111, SF-80101 Joensuu, FinlandSearch for more papers by this author Eero Iiskola, Corresponding Author Eero Iiskola Neste Chemicals, P. O. Box 320, SF-06101 Porvoo, FinlandNeste Chemicals, P. O. Box 320, SF-06101 Porvoo, FinlandSearch for more papers by this authorAija Pelkonen, Aija Pelkonen Neste Chemicals, P. O. Box 320, SF-06101 Porvoo, FinlandSearch for more papers by this authorHeikki J. Kakkonen, Heikki J. Kakkonen University of Joensuu, Department of Chemistry, P. O. Box 111, SF-80101 Joensuu, FinlandSearch for more papers by this authorJouni Pursiainen, Jouni Pursiainen University of Joensuu, Department of Chemistry, P. O. Box 111, SF-80101 Joensuu, FinlandSearch for more papers by this authorTapani A. Pakkanen, Tapani A. Pakkanen University of Joensuu, Department of Chemistry, P. O. Box 111, SF-80101 Joensuu, FinlandSearch for more papers by this author First published: February 1993 https://doi.org/10.1002/marc.1993.030140212Citations: 25AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume14, Issue2February 1993Pages 133-137 RelatedInformation

Stereoselective polymerization of α-olefins by heterogeneous chiral Ziegler-Natta catalysts

MgCl 2 -supported TiCl 3 catalysts were prepared to contain either chiral (racemic or optically active) or nonchiral Lewis basic esters. They were compared along with ordinary TiCl 3 in the stereospecific polymerization of propylene and in the stereoselective and stereoelective polymerization of chiral 3- and 4-methyl-substituted olefins. The number and type of active sites, kinetic parameters, stereoregularity and optical purity of the polymers were determined.

Stereospecific polymerization of propylene in the presence of homogeneous catalysts: ligand-monomer enantioselective interactions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStereospecific polymerization of propylene in the presence of homogeneous catalysts: ligand-monomer enantioselective interactionsPasquale Longo, Antonio Proto, Alfonso Grassi, and Paolo AmmendolaCite this: Macromolecules 1991, 24, 16, 4624–4625Publication Date (Print):August 1, 1991Publication History Published online1 May 2002Published inissue 1 August 1991https://doi.org/10.1021/ma00016a024RIGHTS & PERMISSIONSArticle Views111Altmetric-Citations40LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (237 KB) Get e-Alerts Get e-Alerts

Some novel structural and chemical aspects of Cp-substituted bent metallocene complexes

Abstract

Stereospecific polymerization of propene using MgCl2‐supported Ti catalysts combined with various alkyl titanium compounds

Stereospecific polymerization of propene using MgCl₂‐supported Ti catalysts combined with various alkyl titanium compounds

Stereospecific polymerization of propene using MgCl2‐supported Ti catalysts combined with (RCp)2TiMe2 (RH, Me)

Stereospecific polymerization of propene using MgCl₂‐supported Ti catalysts combined with (RCp)₂TiMe₂ (RH, Me)

The role of some bases in the stereospecific polymerization of propylene with titanium catalysts supported on magnesium chloride

The influence of Lewis bases on the stereospecificity and productivity of catalytic systems of the type MgCl2/TiCl4/AlR3 as well as on microtacticity and molecular weight of the polymer fractions has been systematically investigated using propylene as monomer. The results are in keeping with the hypothesis that beside non stereospecific centers two types of stereospecific catalytic centers exist, in one of which the Lewis base is present. The centers can be classified according to their Lewis acidity, the more acidic centers yielding polymers with lower molecular weight and tacticity. The structure of the Lewis bases is of paramount importance in determining the stereospecificity of the catalytic systems and can be used as a probe to investigate the structure of the different catalytic centers.

Stereospecific polymerization of propylene on systems TiX 3-AlEt 3

It has been shown that replacement of Cl atoms by I and Br atoms leads to decrease in the activity of the catalytis systems TiCl 3-AlEt 3 owing to decrease in the number of active centres. This decrease is probably due to the fact that a group of titanium atoms bound by halogen bridges, and not a single atom, is involved in the catalytis act. The most effective way of enhancing the isospecificity of the active centre is to induce the iodine-containing compound to act upon the TiCl 3 crystal surface. However, no simple correlation between the stereospecificity of the catalytis systems, ion radii of the anions and distances M-M and M-X was found.

Stereospecific Polymerization of Propylene: An Outlook 25 Years after Its Discovery

AbstractIn 1955 Natta and his co‐workers from the Istituto di Chimica Industriale del Politecnico di Milano reported the properties of highly crystalline polypropylene and other poly‐α‐olefins[1] which posses, at least in long sections of the main chain, asymmetric carbon atoms of the same absolute configuration (isotactic poly‐α‐olefins). The discovery of the new crystalline polymers was judged at that time “revolutionary in its significance”[2] and heralded a new era in polymer science and technology. Indeed, crystalline polypropylene, because of its relatively high melting point and its outstanding mechanical properties, has found very extensive application in the field of plastics films and fibers.—25 years after this publication, it is worthwhile examining the further developments following this discovery which has had such a great scientific and industrial impact, and the problems which are still open concerning the structure of the catalytic centers and the mechanisms by which practically completely stereoregular polypropylenes are formed.

Determining the number of active centres and the time of macromolecular extension in stereospecific polymerization of propylene (in connection with the paper by I. Meizlik and M. Lesna)

Results are described of determining the number of active centres and the time of macromolecular extension in stereospecific polymerization of propylene with a TiCl 3+Al(C 2H 5) 2Cl complex catalyst. It is shown that when calculating the number of extension centres and the life time of macromolecules from weight-average molecular weight it is essential to bear in mind the variation of polydispersion of the polymer with temperature and the degree of conversion.

Role of organometal and monomer in the formation of active centers at stereospecific polymerization of propylene

Role of organometal and monomer in the formation of active centers at stereospecific polymerization of propylene

The use of mesitaldehyde to promote stereospecific polymerization of propylene

The use of mesitaldehyde to promote stereospecific polymerization of propylene

Influence of the nature of the organometallic component of the complex catalyst on the kinetics of the stereospecific polymerization of propylene

1. The influence of the nature of the organometallic component in the catalytic system TiCl3-MeRn on the rate of polymerization of propylene, molecular weight, and stereoisomeric composition of the polypropylene formed was studied. 2. The nature of the metal of the organometallic component of the catalyst influences both the number of catalytic centers and their reactivity. 3. The nature of the alkyl group of the organometallic compound exerts little influence in comparison with the metal on the number of catalytic centers, and exerts practically no influence on their reactivity. 4. The stereospecific action of the catalytic system does not depend on the nature of the metal alkyl used as the co-catalyst.

Stereospecific Polymerization of Propylene with Natta Catalyst under Ordinary Pressure

AbstractThe stereospecific polymerization of propylene with Natta catalyst under ordinary pressure has been investigated and discussed. Propylene of 99.5% purity was polymerized with a metal‐organic complex catalyst, formed from A1(C2h5)3 and TiCl3, giving a white or greyish stereopolymer which contained ca. 70% isotactic polypropylene. The optimum conditions of polymerization were as follows: The mole‐ratio of Al(C2H3/TiCl3 was 8–15; the polymerization‐temperature was 70°C, and the concentration of TiCl3 was 0.6–0.8g per 120ml of n‐heptane. The maximum polymerization rate reached the value of 6g C3H6/hr./g TiCl3 and the apparent activation energy as calculated from an Arrheniusplotting line, was 12.1 kcal/mole.

Ziegler-Natta catalysis III. Stereospecific polymerization of propene with the catalyst system TiCl 3AlEt 3

The stereospecificity of the polymerization of propene under the influence of α-TiCl 3 and alkyl aluminum compounds is explained. The explanation rests exclusively on quantum chemical principles and the crystal chemistry of transition metal trichloride layer structures, subjects described in two preceding papers. The active centers formed by alkylation of titanium ions at those faces of the surface where chlorine vacancies are available are shown to possess the asymmetry necessary for the appropriate orientation of the α olefin in the π complex with the exposed titanium. The nonequivalence of the crystallographic sites of vacancy and alkyl group at the active center ensures that the growing alkyl group will move back to its original position after each incorporation of a new monomer. Thus the polymerization consists of a sequence of sterically identical steps which leads to isotacticity of the product.