Download or read book Synthesis of Group 4 Metal Octahedral Bis phenolate Complexes for Propylene Polymerization written by Madalyn Radlauer and published by . This book was released on 2008 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Octahedral Bis phenolate Ether Group IV Metal Complexes for Polymerization and Copolymerization of Alpha olefins written by Elizabeth Tanzini Kiesewetter and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Octahedral group IV bis(phenolate) ether complexes, activated by methylaluminoxane, are highly active and stereospecific [alpha]-olefin polymerization catalysts. X-ray crystallographic analysis reveals the Zr and Hf complexes to be closely isostructural; the bond lengths of the Hf complex are slightly shorter, but the maximum deviation is only 0.062 Å. Despite the structural similarity of the Hf and Zr complexes, the Hf complexes generate more highly stereoselective catalysts. In addition to the influence of the transition metal, the structure of the ligand has a large influence on the stereospecificity. Bis-t-Butyl phenyl substituted complexes of Hf and Zr, when activated by MAO at 50 - 80 °C, generate high molecular weight polypropylene (Mn = 130,000 - 360,000 g/mol) with isotacticities [mmmm]> 0.97 and melting points as high as 165°C. Octahedral group IV bisphenolate ether complexes, activated by methylaluminoxane, were also tested in propylene polymerization in the presence diethyl zinc. Although the Hf and Zr complexes are structurally similar, propylene polymerization behavior of the two catalysts differs significantly in terms of productivity, isospecificity and propensity to incorporate specific regioerrors. 13C-NMR analysis revealed that the type and the number of regioerrors being incorporated into the polymer chain are strongly dependent on the identity of the ligand and the metal. Low molecular weight polypropylene oligomers (Mn = 1700 - 9900 g/mol), generated in the presence of diethyl zinc facilitated end group analysis, which revealed the presence of isobutyl and 2-methylbutyl groups. Octahedral bis(phenolate) catalysts are highly active catalysts for the isospecific polymerization of 1-hexene and the production of high molecular weight ethylene/1-hexene copolymers. These catalysts are active for the production of high molecular weight copolymers even at high temperatures. The reactivity ratios for these complexes were determined; all of the bis(phenolate) complexes tested showed reasonable 1-hexene incorporations. The complexes prepared from the more sterically demanding ligands showed higher incorporations of comonomers than those prepared from the less sterically demanding ligands. Complexes of the type Cp*TiX2(ONR'R'') (Cp* = [Eta]5-C5Me5, X = Me, Cl; R = Et, TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl); X = R' = Me, R'' = tBu) were synthesized by several routes. Upon activation with [Ph3C]+[B(C6F5)4]- and AliBu3, these complexes generate highly active catalysts for propylene polymerization, although significant catalyst deactivation was observed. Activation with B(C6F5)3/AliBu3 or methylaluminoxane (MAO) resulted in reduced polymerization activity; the latter leading to increased catalyst lifetime. Reaction of Cp*Ti(Me)2(ONEt2) and Cp*Ti(Me)2(ONtBu(Me)) with B(C6F5)3 resulted in clean formation of the zwitterionic contact ion pairs, [Cp*Ti(Me)([Eta]2-ONEt2)]+[MeB(C6F5)3]- and [Cp*Ti(Me)([Eta]2-ONtBu(Me))]+[MeB(C6F5)3]- respectively whereas reaction of Cp*Ti(Me)2([Eta]2-ONtBu(Me)) with [Ph3C]+[B(C6F5)4]- resulted in the clean formation of the solvent-separated ion pair [Cp*Ti(Me)([Eta]2-ONtBu(Me))]+[B(C6F5)4]-. Addition of AliBu3 or AlMe3 to the cationic [Cp*Ti(Me)(ONtBu(Me))]+[B(C6F5)4]- resulted in decomposition of the cations.
Download or read book Group 4 Complexes Bearing Tridentate Aryloxide Based Ancillary Ligands written by Ka-Ho Tam and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Group 4 Complexes Bearing Tridentate Aryloxide-based Ancillary Ligands: Synthesis, Characterization and Application as Olefin Polymerization Catalysts" by Ka-ho, Tam, 譚家豪, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled GROUP 4 COMPLEXES BEARING TRIDENTATE ARYLOXIDE- BASED ANCILLARY LIGANDS: SYNTHESIS, CHARACTERIZATION AND APPLICATION AS OLEFIN POLYMERIZATION CATALYSTS Submitted by Tam Ka Ho for the degree of Doctor of Philosophy at The University of Hong Kong in 2006 The preparation, characterization, crystal structures and olefin polymerization behavior of a class of Group 4 complexes, and in particular the Zr(IV) derivatives 1 1 [Zr(L )Cl (D)] [H L = 2,6-di(3-tert-butyl-5-methylphen-2-ol)pyridine; D = ethers, 2 2 ketones and Cl(HPR )], have been undertaken. These [O, N, O] catalysts exhibit excellent activities with MAO for ethylene polymerization. Studies to assess the impact of the donor group during catalysis suggest that the same active species is generated and the donor does not play an active role. Superior activities were observed with the Bu Al/Ph CB(C F ) cocatalyst in ethylene polymerization and - 3 3 6 5 4 -1 -1 propylene copolymerization (36,590 and 15,700 g mmol h respectively). Insight into the behavior of the catalytic system with MAO has been derived from gel permeation chromatography and NMR analyses of the polymers prepared under 1 13 different reaction conditions. H and C NMR end-group analyses reveal resonances for saturated methyl chain-end groups only, and undetectable levels of unsaturated vinyl chain ends. This indicates that for the polymerization chain-transfer mechanism, the conventional β-H transfer reactions are insignificant and the unusual chain transfer to Al pathway is vastly dominant. Group 4 complexes supported by unsymmetric tridentate [O, N, O] ligands bearing different substituents on the two aryloxide rings have been prepared, in order to develop new catalytic systems capable of stereospecific α-olefin polymerization. Their activities for ethylene polymerization with MAO are significantly lower than the symmetric [O, N, O] analogues. A number of group 4 bis(benzyl) complexes supported by tridentate pyridine-2- phenolate-6-aryl [O, N, C] ligands, with alkyl and halogen substituents at the R position ortho to the metal, have been prepared. This enabled direct comparison with the CF -substituted [O, N, C] analogues, which were recently reported to exhibit novel C-H---F-C contacts in solution with potential applications for attractive ligand---polymer interactions. The molecular structure of the Zr derivative bearing an ortho-Cl group was determined, revealing the benzyl moieties in an unusual 'anti, anti' configuration. Saliently, this polyethylene catalyst in conjunction with Bu Al/Ph CB(C F ) displayed the best activity thus far observed for [O, N, C] 3 3 6 5 4 -1 -1 catalysts (8630 g mmol h ). A series of group 4 bis(benzyl) complexes supported by newly designed [O, C, N] ligands bearing R substituents ortho to the metal has been prepared, such that the σ- aryl moiety resides trans to the alkyl/polymer chain, and catalyst decomposition pathways such as olefin insertion into the M-C(sp ) bond are impeded. The crystal structure of the CF -substituted hafnium(IV) complex features weak intramolecular 31 C-H---F-C (CF ---methylene) interactions. The H NMR spectra of [M(O, C, N- CF )(CH Ph) ] analogues revealed coupling (assigned to J [via M---F] for Hf and
Download or read book Group 4 Metal Octahedral Complexes as Catalysts for Olefin Polymerization written by Marina Lamberti and published by . This book was released on 2003 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis of Group 4 Metal diketimine Complexes written by William James Scanlon and published by . This book was released on 1998 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Designing Octahedral Group 4 Complexes as Catalysts for Polymerization Processes written by and published by . This book was released on 2009 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis and Characterization of Group 4 Complexes and Olefin Polymerization Catalysts Supported by Chelating V aryl Ligands written by Chun Yu Lo and published by . This book was released on 2009 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Amine bis phenolate Complexes of Chromium for Carbon Dioxide cyclohexene Oxide Copolymerization and Group I and II Complexes for the Ring Opening Polymerization of Rac lactide written by Katalin Devaine-Pressing and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Finding novel methods for polymer synthesis has been of particular interest as of late from both a chemical and commercial standpoint. This focus stems from the recognized need for biodegradable and biocompatible polymers, originating from renewable resources, and is a legitimate endeavor by society to ease the burden imposed on the environment. Society's conscience also recognizes the great need to utilize the carbon dioxide that is released in the atmosphere and it continues to make noble efforts in order not to contribute further to the greenhouse effect caused by greenhouse gases such as carbon dioxide. Therefore, the use of carbon dioxide as a starting material and the incorporation of it in the product of a chemical synthesis are currently developing research areas. Accordingly, combining the aim of environmentally friendly polycarbonate synthesis with incorporation of carbon dioxide in the polymer chain was the goal of the research conducted in the first part of this thesis. Additionally, biodegradable and biocompatible polylactide from lactide, originating from renewable feedstocks, was produced by biocompatible complexes in the second part. Polycarbonate synthesis was carried out in the presence of novel chromium(III) catalysts which were synthesized via salt metathesis reactions from tetradentate tripodal amine-bis(phenol) ligands. The complexes were characterized by MALDI-TOF mass spectrometry, UV-Vis and IR spectroscopy, magnetic susceptibility measurement and elemental analysis. The catalyst precursors selectively produced polycarbonates from epoxides and carbon dioxide with high yields and moderate molecular weights. Mechanistic studies revealed a first order dependence on catalyst concentration and that ring opening of the epoxide was initiated by a nucleophilic species originating either from the complex or from an externally added nucleophile. Biocompatible magnesium-, lithium-, sodium-, potassium- and calcium complexes of an amino-bis(phenolato) ligand were also prepared and characterized for the synthesis of polylactide, a biodegradable and biocompatible polymer. The magnesium and the sodium complexes in particular showed high catalytic activity and good control over the reaction. The complexes were active even under relatively low catalyst loading (0.1 - 0.2 mol%) and produced polymers of high purity as revealed by NMR, DSC and TGA.
Download or read book Group 4 Metal and Vanadium Bis phenolato Complexes written by Geert Johannes Marinus Meppelder and published by . This book was released on 2009 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis of Group IV Transition Metal Complexes and Their Applications as Catalysts for Ethylene Polymerization written by Khalil Ahmad and published by . This book was released on 2010 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Group 4 Complexes Bearing Tridentate Aryloxide based Ancillary Ligands written by Ka-ho Tam and published by . This book was released on 2006 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis Characterization and Oxidation of New Divalent Lanthanide Bis phenolate Complexes and Their Applications in the Ring Opening Polymerization of Cyclic Esters written by Divine Timah Dugah and published by . This book was released on 2009 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Group 4 Complexes Bearing Tridentate Aryloxide based Ancillaryligands written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Late Transition Metal Polymerization Catalysis written by Bernhard Rieger and published by John Wiley & Sons. This book was released on 2006-03-06 with total page 345 pages. Available in PDF, EPUB and Kindle. Book excerpt: At the start of the 1950s, Ziegler and Natta discovered that simple metallorganic catalysts are capable of transforming olefins into linear polymers with highly ordered structures. This pioneering discovery was recognized with a Nobel Prize in 1963. In the 80s and 90s, the development of molecular defined metallocenes led to a renaissance for non-polar polyolefin materials. Designer catalysts allowed a greater precision in defining properties of the material. The past 10 years have seen the discovery of new catalysts based on late transition metals, which allow the combination of polar monomers with non-polar olefins and thus lead to innovative materials. Here, the world's leading authors from industry and academia describe the latest developments in this fascinating field for the first time in such comprehensive detail. In so doing, they introduce readers systematically to the basic principles and show how these new catalysts can effectively be used for polymerization reactions. This makes the book an ideal and indispensable reference for specialists, advanced students, and scientists of various disciplines dealing with research into catalysts and materials science.
Download or read book Zeitschrift F r Naturforschung written by and published by . This book was released on 2004 with total page 762 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Surface Organometallic Chemistry Molecular Approaches to Surface Catalysis written by Jean-Marie Basset and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface organometallic chemistry is a new field bringing together researchers from organometallic, inorganic, and surface chemistry and catalysis. Topics ranging from reaction mechanisms to catalyst preparation are considered from a molecular basis, according to which the "active site" on a catalyst surface has a supra-molecular character. This. the first book on the subject, is the outcome of a NATO Workshop held in Le Rouret. France, in May. 1986. It is our hope that the following chapters and the concluding summary of recommendations for research may help to provide a definition of surface organometallic chemistry. Besides catalysis. the central theme of the Workshop, four main topics are considered: 1) Reactions of organometallics with surfaces of metal oxides, metals. and zeolites; 2) Molecular models of surfaces, metal oxides, and metals; 3) Molecular approaches to the mechanisms of surface reactions; 4) Synthesis and modification of zeolites and related microporous solids. Most surface organometallic chemistry has been carried out on amorphous high-surf ace-area metal oxides such as silica. alumina. magnesia, and titania. The first chapter. contributed by KNOZINGER. gives a short summary of the structure and reactivity of metal oxide surfaces. Most of our understanding of these surfaces is based on acid base and redox chemistry; this chemistry has developed from X-ray and spectroscopic data, and much has been inferred from the structures and reactivities of adsorbed organic probe molecules. There are major opportunities for extending this understanding by use of well-defined (single crystal) oxide surfaces and organometallic probe molecules.
Download or read book Olefin Polymerization written by Walter Kaminsky and published by Wiley-VCH. This book was released on 2006-08-18 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: With an enormous velocity, olefin polymerization has expanded to one of the most significant fields in polymers since the first industrial use about 50 years ago. In 2005, 100 million tons of polyolefins were produced - the biggest part was catalyzed by metallorganic compounds. The Hamburg Macromolecular Symposium 2005 with the title "Olefin Polymerization" involved topics such as new catalysts and cocatalysts, kinetics, mechanism and polymer reaction engineering, synthesis of special polymers, and characterization of polyolefins. The conference combined scientists from different disciplines to discuss latest research results of polymers and to offer each other the possibility of cooperation. This is reflected in this volume, which contains invited lectures and selected posters presented at the symposium.
