DOCSLIB.ORG

The Use of Functionalized Zirconocenes As Precursors to Silica-Supported Zirconocene Olefin Polymerization Catalysts

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

THE USE OF FUNCTIONALIZED ZIRCONOCENES AS PRECURSORS TO SILICA-SUPPORTED ZIRCONOCENE OLEFIN POLYMERIZATION CATALYSTS by Cheng, Xu A Dissertation Submitted to the Faculty of the Virginia Polytechnic Institute and State University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Chemistry Paul A. Deck, Chairman Karen J. Brewer Brian E. Hanson Timothy E. Long James M. Tanko Dec. 10th, 2001 Department of Chemistry Virginia Tech Blacksburg, Virginia Keywords: Synthesis, Organometallic, Zirconocene, Stannyl, Silyl, Electrophilic Substitution, Hydrolysis, Polyolefin Catalyst, MAO, Immobilization, Silica, Leaching Copyright 2001, Cheng, Xu Abstract Me3Si substituents adjacent to Cp2MCl2 (M = Ti, Zr, Hf) are converted to BrMe2Si groups using BBr3. The high reactivity of the Si-Br bonds toward nucleophiles such as water suggested that these substituents could react with hydroxylated silica surfaces, immobilizing the metallocenes. This dissertation concerns the syntheses of electrophile-functionalized zirconocene dihalide complexes and their use as precursors to silica-supported metallocene olefin polymerization catalysts. First we extended the metallocene “functionalization” chemistry to obtain substituents bearing more than one electrophilic bond. (Me3Sn)2C5H4 combined with CpZrCl3 in toluene to 5 afford (h -Me3Sn-C5H4)CpZrCl2 (A). Reactions of A with electrophiles (E-X = Cl2B-Cl, I-Cl, 5 and I-I) afforded (h -XMe2Sn-C5H4)CpZrCl2 (and E-Me) cleanly. The reaction of A with BBr3 5 5 afforded either (h -BrMe2Sn-C5H4)CpZrBr2 (25 °C, 10 min) or (h -Br2MeSn-C5H4)CpZrBr2 (25 5 °C, 15 h). Ph2MeSi-C5H4Li combined with ZrCl4•2THF to afford (h -Ph2MeSi-C5H4)2ZrCl2 (B). The reaction of B with BCl3 led to incomplete cleavage of the Ph-Si bonds, however treatment of 5 5 B with BBr3 afforded (h -Br2MeSi-C5H4)2ZrBr2 (C) efficiently. X-ray crystal structures of (h - 5 ClMe2Sn-C5H4)CpZrCl2•½toluene, (h -Br2MeSn-C5H4)CpZrBr2•THF, B, and C were obtained. Metallocene C reacts with water to afford an oligosiloxane-supported zirconocene dibromide. Spectroscopic characterization suggested a stereoregular structure in which the metallocene units have meso symmetry. The oligomeric substance showed high activity for homogeneous ethylene polymerization. Supported metallocene olefin polymerization catalysts were prepared by combining a functionalized metallocene precursor (Cp2ZrBr2 bearing either BrMe2Si or Br2MeSi groups) and partially dehydroxylated silica. The activities of the immobilized zirconocene catalysts ii decreased and the stabilities increased with increasing number of tethers. The immobilized 5 catalyst prepared from (h -Br2MeSi-C5H4)2ZrBr2, which is assumed to form two “double- tethers” to silica, was significantly more active than the catalyst prepared from [h5-1,3- (BrMe2Si)2C5H3]2ZrBr2, which is assumed to form four “single-tethers” to silica. Catalyst leaching was observed in all the immobilized zirconocene catalysts. Finally we report model studies on the stability of the Si-O-Si bonds toward 5 t methylaluminoxane (MAO). The reaction of (h -BrMe2Si-C5H4)CpZrBr2 with BuMe2SiOH results in the formation of Si-O-Si bonds; addition of NEt3 results in further reaction to afford Si- O-Zr bonds. The reaction of Me3Si-O-SiMe3 with MAO showed that Si-O-Si bonds can be cleaved under the conditions of our polymerization reactions. iii Acknowledgements I sincerely thank my advisor, Prof. Paul A. Deck, for his great support and guidance in my graduate research for the Ph. D. degree at Virginia Tech. Under his supervision, I learned a lot of synthetic organometallic methods and techniques, as well as methods and techniques for heterogeneous catalytic olefin polymerization. It has been a great opportunity and experience for me to work in his group. I sincerely appreciate his great help. I am grateful to my committee members, Professors Karen Brewer, Brian Hanson, Timothy Long, and James Tanko, for their kind help during the course of my research and graduate study. I also want to thank William Bebout and Tom Glass of the Analytical Service for their help with the NMR instrument, and Ms. Judy Gunderson of Dow Chemical for her kind work in obtaining the GPC data of polyethylene samples. I also got a lot of help in my research from my group partners in the past two years. They are Francisco Cavadas, Eric Hawrelak, Owen Lofthus, Matthew Thornberry, and Andrea Warren. Their friendship encouraged me to overcome many difficulties. I wish to take this opportunity to thank them. This research was supported by the National Science Foundation (CHE-9875446) and Research Corporation (CS0567). I appreciate their financial support. Finally, without the edification, support, and endless love from my parents, I would not have been the person I am. They were, are, and will be forever the most important source of encouragement to me. This dissertation is dedicated to them. iv Table of Contents Chapter 1 Introduction................................................................................................................. 1 1.1 Polyethylenes and Methods to Produce Polyethylenes.......................................................... 1 1.1.1 Classification of Polyethylenes and Their Applications............................................... 1 1.1.2 Free Radical Polymerization......................................................................................... 3 1.1.3 Coordination Polymerization Using Ziegler-Natta Catalysts ....................................... 5 1.1.3.1 The Solution Polymerization Process ..................................................................... 9 1.1.3.2 The Bulk Polymerization Process........................................................................... 9 1.1.3.3 The Slurry Polymerization Process......................................................................... 9 1.1.3.4 The Gas-Phase Polymerization Process................................................................ 10 1.2 Metallocene Catalysts.......................................................................................................... 13 1.2.1 Development of Metallocene Catalysts ...................................................................... 13 1.2.2 Synthesis, Structure and Property of Aluminoxanes .................................................. 15 1.2.2.1 Synthesis of Aluminoxanes................................................................................... 15 1.2.2.2 Structures and Properties of Aluminoxanes.......................................................... 17 1.2.3 Advantages of Metallocene Catalysts......................................................................... 20 1.2.4 Disadvantages of Metallocene Catalysts .................................................................... 24 1.2.5 Mechanism of Metallocene Catalyzed Olefin Polymerization ................................... 26 1.2.5.1 Some Proposed Mechanisms ................................................................................ 26 1.2.5.2 Formation of Active Sites and the Role of MAO ................................................. 29 1.3 Supported Metallocene Catalysts......................................................................................... 31 1.3.1 Supported Metallocene Catalysts on Silica................................................................. 32 1.3.1.1 General Features of Silica..................................................................................... 33 1.3.1.2 Direct Deposition.................................................................................................. 37 1.3.1.3 Pre-alumination..................................................................................................... 39 1.3.1.4 Covalent Tethering................................................................................................ 42 1.3.2 Metallocene Catalysts Supported on Other Materials ................................................ 48 1.4 New Immobilization Strategy and Goals of the Research................................................... 56 1.4.1 Proposal for a New Immobilization Method Using Multiple Short Covalent Tethers56 1.4.2 Achievements in the Syntheses of Group 4 Metallocene Compounds Containing Multiple Halosilyl Groups ............................................................................................. 58 1.4.3 Goals of the Research ................................................................................................. 61 Chapter 2 Synthesis and Reactivity of Trimethylstannyl Zirconocene Dichloride [(h5- Me3Sn-C5H4)CpZrCl2].......................................................................................................... 63 2.1 Introduction: Comparison between Silicon and Tin............................................................ 63 5 2.2 Synthesis of (h -Me3Sn-C5H4)CpZrCl2 ............................................................................... 66 v 2.2.1 Discussion of the Synthetic Route.............................................................................. 66 5 2.2.2 Synthesis and Characterization of (h -Me3Sn-C5H4)CpZrCl2 .................................... 69 2.2.3 Discussion of the Synthetic Conditions and Origins of Some Impurities .................. 70 5 2.3 Reactivity of (h -Me3Sn-C5H4)CpZrCl2 with Electrophiles................................................ 73 5 2.3.1 Reaction of (h -Me3Sn-C5H4)CpZrCl2 with BCl3 ...................................................... 73 5 2.3.2 Reaction of (h -Me3Sn-C5H4)CpZrCl2
Recommended publications
  • Transmetalation

    Transmetalation

    Organic Chemistry IV Organometallic Chemistry for Organic Synthesis Prof. Paul Knochel LMU 2015 1 OCIV Prüfung: Freitag 17. Juli 2015 9-11 Uhr Wieland HS Wiederholungsklausur: Donnerstag 17. September 2015 12-14 Uhr Baeyer HS 2 Recommended Literature 1. F. A. Carey, R. J. Sundberg, Advanced Organic Chemistry, Fifth Edition Part A and Part B, Springer, 2008, ISBN-13: 978-0-387-68346-1 2. R. Brückner, Organic Mechanisms, Springer, 2010, ISBN: 978-3-642- 03650-7 3. L. Kürti, B. Czako, Strategic applications of named reactions in organic synthesis, Elsevier, 2005, ISBN-13: 978-0-12-429785-2 4. N. Krause, Metallorganische Chemie, Spektrum der Wissenschaft, 1996, ISBN: 3-86025-146-5 5. R. H. Crabtree, The organometallic chemistry of transition metals, Wiley- Interscience, 2005, ISBN: 0-471-66256-9 6. M. Schlosser, Organometallics in Synthesis – A manual, 2nd edition, Wiley, 2002, ISBN: 0-471-98416-7 7. K. C. Nicolaou, T. Montagnon, Molecules that changed the world, Wiley- VCH, 2008, ISBN: 978-527-30983-2 8. J. Hartwig, Organotransition Metal Chemistry: From Bonding to Catalysis, Palgrave Macmillan, 2009, ISBN-13: 978-1891389535 9. P. Knochel, Handbook of Functionalized Organometallics, Volume 1 und 2, Wiley-VCH, 2005, ISBN-13: 978-3-527-31131-6 3 Importance of organometallics 4 Industrial production Industrial annual production of various organometallics Organometallic production [T / year] Si 700 000 Pb 600 000 Al 50 000 Sn 35 000 Li 900 5 Organometallic reagents and catalysts for the organic synthesis 6 Historic point of view 1757 - Louis Cadet de Gassicourt (parisian apothecary) E. Frankland (1848), University of Marburg, initial goal: synthesis of an ethyl radical Universität Marburg (1848) 7 Organometallic chemistry of the XIX century 8 Organometallic chemistry of the XIX century 9 Reactivity of the Grignard reagents 10 Historic point of view Victor Grignard (1900) Karl Ziegler (1919) 11 Historic point of view first transition metal organometallics: Hein (1919) 12 Historic point of view 1951 : synthesis of ferrocene Pauson (Scotland) 7.
  • Donor/Acceptor Metallocenes: a New Structure Principle in Catalyst Design

    Donor/Acceptor Metallocenes: a New Structure Principle in Catalyst Design

    COMMUNICATIONS metal complex inside their tunnels, which makes these [19] C. Cascales, E. GutieÂrrez-Puebla, M. A. Monge, C. Ruiz-Valero, materials a good point of departure for designing new Angew. Chem. 1998, 110, 135 ± 138; Angew. Chem. Int. Ed. 1998, 37, 129 ± 131. catalysts; a stable framework after removal of the transition [20] H. Li, M. Eddaaoudi, D. A. Richardson, O. M. Yaghi, J. Am. Chem. metal complex; and large distances between the active metal Soc. 1998, 120, 8567. centers, which allows unhindered access of reactants to these [21] Hailian Li, O. M. Yaghi, J. Am. Chem. Soc. 1998, 120, 10569. centers through uniformly sized 8Rc channels. [22] T. E. Gier, X. Bu, P. Feng, G. D. Stucky, Nature 1998, 395, 154. [23] X. Bu, P. Feng, G. D. Stucky, J. Am. Chem. Soc. 1998, 120, 11204. [24] X. Bu, P. Feng, T. E. Gier, D. Zhao, G. D. Stucky, J. Am. Chem. Soc. 1998, 120, 13389. [25] H. Brumer, K. Wutz, New J. Chem. 1992, 16,57. Experimental Section [26] A. Corma, V. ForneÂs, S. B. Pergher, T. L. Maesennn, J. G. Buglass, Nature 1998, 396, 353. [27] SHELXTL, Siemens Energy & Automation Inc., Analytical Instru- X-ray structure analysis of ICMM-2Cu, ICMM-2Ag, and ICMM-2H: mentation, 1996. Orthorhombic, space group Pnna,MoKa, dimensions of crystals: 0.2 Â 0.1 Â 0.05, 0.02 Â 0.08 Â 0.2, and 0.04 Â 0.16 Â 0.2 mm, respectively; see Table 1 for the cell parameters. Data were collected in a Siemens SMART- CCD diffractometer using w scans over the range 3 < q < 268.
  • University of Groningen Structural Characterization of a Cationic Zirconocene Olefin Polymerization Catalyst with Its Methylated

    University of Groningen Structural Characterization of a Cationic Zirconocene Olefin Polymerization Catalyst with Its Methylated

    University of Groningen Structural characterization of a cationic zirconocene olefin polymerization catalyst with its methylated boralumoxane counterion Richter, Bodo; Meetsma, Auke; Hessen, Bart; Teuben, Jan H. Published in: Angewandte Chemie-International Edition in English IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2002 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Richter, B., Meetsma, A., Hessen, B., & Teuben, J. H. (2002). Structural characterization of a cationic zirconocene olefin polymerization catalyst with its methylated boralumoxane counterion. Angewandte Chemie-International Edition in English, 41(12), 2166 - 2169. Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date: 10-02-2018 COMMUNICATIONS A. P. Wheeler, A. Veis, A. I. Caplan, Science 1992, 255, 1098 ± Structural Characterization of a Cationic 1105. [4] P. Calvert, P.
  • Theoretical Insight Into the Transmetalation of MOF-5 Lattices

    Theoretical Insight Into the Transmetalation of MOF-5 Lattices

    Article pubs.acs.org/cm When the Solvent Locks the Cage: Theoretical Insight into the Transmetalation of MOF‑5 Lattices and Its Kinetic Limitations ,† ‡ †,§ ‡ † Luca Bellarosa,* Carl K. Brozek, Max García-Melchor, Mircea Dinca,̆and Nuriá Lopeź † Institute of Chemical Research of Catalonia, ICIQ, Av. Països Catalans 16, 43007 Tarragona, Spain ‡ Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States § SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States *S Supporting Information ABSTRACT: Transmetalation is an innovative postsynthetic strategy for tailoring the properties of metal−organic frameworks (MOFs), allowing stable unprecedented metal coordination environments. Although the experimental synthetic protocol is well- established, the underlying mechanism for transmetalation is still unknown. In this work, we propose two different solvent-mediated reaction paths for the Ni transmetalation in Zn- MOF-5 lattices through density functional theory simulations. In both mechanisms, the bond strength between the exchanged metal and the solvent is the key descriptor that controls the degree of transmetalation. We also show that the role of the solvent in this process is twofold: it initially promotes Zn exchange, but if the metal−solvent bond is too strong, it blocks the second transmetalation cycle by restricting the lattice flexibility. The competition between these two effects leads the degree of incorporation of metal into MOF-5 to display a volcano-type dependence with respect to the metal−solvent bond strength for different transition metal ions. ■ INTRODUCTION PSIM.26 Nevertheless, the dependence on the ligand field was The easiness with which metal−organic frameworks (MOFs)1 found to be opposite for Ni inserting into MOF-5 and Co into MFU-4l.
  • Oxidation of Organocopper Compounds

    Oxidation of Organocopper Compounds

    Oxidation of Organocopper Compounds Sarah J. Aves and Dr. David R. Spring Department of Chemistry University of Cambridge Lensfield Road Cambridge CB2 1EW United Kingdom Tel.: +44 (0) 1223 336498 Fax: +44 (0) 1223 336362 E-mail: [email protected] [email protected] Oxidation of Organocopper Compounds Contents I. Introduction.................................................................................................................3 II. Formation of C-C Bonds............................................................................................. 4 A. Initial Studies.......................................................................................................... 4 B. Cross-coupling ........................................................................................................ 5 C. Biaryl Formation................................................................................................... 11 D. Intramolecular Bond Formation............................................................................ 14 E. Dimerisations of Heteroaromatics, Alkenyl and Alkyl Groups and Macrocycle Formation...................................................................................................................... 18 III. Formation of C-N Bonds ...................................................................................... 21 A. Initial Studies........................................................................................................ 21 B. Further Developments..........................................................................................
  • Organometallic and Catalysis

    Organometallic and Catalysis

    ORGANOMETALLIC AND CATALYSIS Dr. Malay Dolai, Assistant Professor, Department of Chemistry, Prabhat Kumar College, Contai, Purba Medinipur-721404, WB, India. 1.Introduction Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkaline, alkaline earth, and transition metals, and sometimes broadened to include metalloids like boron, silicon, and tin, as well. Aside from bonds to organyl fragments or molecules, bonds to 'inorganic' carbon, like carbon monoxide (metal carbonyls), cyanide, or carbide, are generally considered to be organometallic as well. Some related compounds such as transition metal hydrides and metal phosphine complexes are often included in discussions of organometallic compounds, though strictly speaking, they are not necessarily organometallic. The related but distinct term "metalorganic compound" refers to metal-containing compounds lacking direct metal-carbon bonds but which contain organic ligands. In 1827, Zeise's salt is the first platinum- olefin complex: K[PtCl3(C2H4)].H2O, the first invented organometallic compound. Organometallic compounds find wide use in commercial reactions, both as homogeneous catalysis and as stoichiometric reagents For instance, organolithium, organomagnesium, and organoaluminium compounds, examples of which are highly basic and highly reducing, are useful stoichiometrically, but also catalyze many polymerization reactions. Almost all processes involving carbon monoxide rely on catalysts, notable examples being described as carbonylations. The production of acetic acid from methanol and carbon monoxide is catalyzed via metal carbonyl complexes in the Monsanto process and Cativa process. Most synthetic aldehydes are produced via hydroformylation. The bulk of the synthetic alcohols, at least those larger than ethanol, are produced by hydrogenation of hydroformylation- derived aldehydes.
  • Nbcl5-Mg Reagent System in Regio- and Stereoselective Synthesis of (2Z)-Alkenylamines and (3Z)-Alkenylols from Substituted 2-Alkynylamines and 3-Alkynylols

    Nbcl5-Mg Reagent System in Regio- and Stereoselective Synthesis of (2Z)-Alkenylamines and (3Z)-Alkenylols from Substituted 2-Alkynylamines and 3-Alkynylols

    molecules Article NbCl5-Mg Reagent System in Regio- and Stereoselective Synthesis of (2Z)-Alkenylamines and (3Z)-Alkenylols from Substituted 2-Alkynylamines and 3-Alkynylols Rita N. Kadikova *, Azat M. Gabdullin, Oleg S. Mozgovoj, Ilfir R. Ramazanov and Usein M. Dzhemilev Institute of Petrochemistry and Catalysis of Russian Academy of Sciences, 141 Prospekt Oktyabrya, 450075 Ufa, Russia; [email protected] (A.M.G.); [email protected] (O.S.M.); ilfi[email protected] (I.R.R.); [email protected] (U.M.D.) * Correspondence: [email protected] Abstract: The reduction of N,N-disubstituted 2-alkynylamines and substituted 3-alkynylols using the NbCl5–Mg reagent system affords the corresponding dideuterated (2Z)-alkenylamine and (3Z)- alkenylol derivatives in high yields in a regio- and stereoselective manner through the deuterolysis (or hydrolysis). The reaction of substituted propargylamines and homopropargylic alcohols with the in situ generated low-valent niobium complex (based on the reaction of NbCl5 with magnesium metal) is an efficient tool for the synthesis of allylamines and homoallylic alcohols bearing a 1,2-disubstituted double bond. It was found that the well-known approach for the reduction of alkynes based on the use of the TaCl5-Mg reagent system does not work for 2-alkynylamines and 3-alkynylols. Thus, this article reveals a difference in the behavior of two reagent systems—NbCl5-Mg and TaCl5-Mg, Citation: Kadikova, R.N.; Gabdullin, in relation to oxygen- and nitrogen-containing alkynes. A regio- and stereoselective method was A.M.; Mozgovoj, O.S.; Ramazanov, developed for the synthesis of nitrogen-containing E-β-chlorovinyl sulfides based on the reaction of I.R.; Dzhemilev, U.M.
  • Carbometallation Chemistry

    Carbometallation Chemistry

    Carbometallation chemistry Edited by Ilan Marek Generated on 01 October 2021, 10:03 Imprint Beilstein Journal of Organic Chemistry www.bjoc.org ISSN 1860-5397 Email: [email protected] The Beilstein Journal of Organic Chemistry is published by the Beilstein-Institut zur Förderung der Chemischen Wissenschaften. This thematic issue, published in the Beilstein Beilstein-Institut zur Förderung der Journal of Organic Chemistry, is copyright the Chemischen Wissenschaften Beilstein-Institut zur Förderung der Chemischen Trakehner Straße 7–9 Wissenschaften. The copyright of the individual 60487 Frankfurt am Main articles in this document is the property of their Germany respective authors, subject to a Creative www.beilstein-institut.de Commons Attribution (CC-BY) license. Carbometallation chemistry Ilan Marek Editorial Open Access Address: Beilstein J. Org. Chem. 2013, 9, 234–235. Schulich Faculty of Chemistry, Technion-Israel Institute of doi:10.3762/bjoc.9.27 Technology, Haifa 32000, Israel Received: 24 January 2013 Email: Accepted: 29 January 2013 Ilan Marek - [email protected] Published: 04 February 2013 This article is part of the Thematic Series "Carbometallation chemistry". Keywords: carbometallation Guest Editor: I. Marek © 2013 Marek; licensee Beilstein-Institut. License and terms: see end of document. Following the pioneering Ziegler addition of nucleophiles to in the 1,2-bisalkylation of nonactivated alkenes! In this nonactivated unsaturated carbon–carbon bonds, the controlled Thematic Series, you will find
  • Room-Temperature Catalytic Hydrodefluorination of Pentafluoro

    Room-Temperature Catalytic Hydrodefluorination of Pentafluoro

    Journal of Molecular Catalysis A: Chemical 261 (2007) 184–189 Room-temperature catalytic hydrodefluorination of pentafluoro-pyridine by zirconocene fluoro complexes and diisobutylaluminumhydride Ulrike Jager-Fiedler¨ a, Marcus Klahn a, Perdita Arndt a, Wolfgang Baumann a, Anke Spannenberg a, Vladimir V. Burlakov b,1, Uwe Rosenthal a,∗ a Leibniz-Institut f¨ur Katalyse e.V. an der Universit¨at Rostock, Albert-Einstein-Str. 29a, D-18059 Rostock, Germany b A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov St. 28, 117813 Moscow, Russia Received 5 May 2006; received in revised form 9 June 2006; accepted 12 June 2006 Available online 11 September 2006 Dedicated to Professor Bernhard Lucke¨ on the occasion of his 70th birthday Abstract ␩5 Mixtures consisting of zirconocene difluorides Cp2ZrF2 (Cp = substituted or nonsubstituted -cyclopentadienyl) as pre-catalysts and diisobutylaluminumhydride i-Bu2AlH as activator were found to be active catalysts in the room-temperature hydrodefluorination (HDF) of fluorinated pyridines. Evaluation of these systems established rac-(ebthi)ZrF2 (1) and Cp2ZrF2 (3) together with i-Bu2AlH as active catalysts in the room-temperature hydrodefluorination (HDF) of pentafluoro-pyridine. The active species for the conversion were the actually formed hydrides [rac-(ebthi)ZrH(␮-H)]2 (2) and [Cp2ZrH(␮-H)]2 (4). The results we obtained (rt, 24 h, turn over number 67) showed a significantly better performance compared to other investigations published before for this HDF reaction. © 2006 Elsevier B.V. All rights reserved. Keywords: Zirconocene; C F bond activation; C H bond activation; Organometallics; Heterocycles 1. Introduction complex Cp2Ti(F)[(O–C(CCF3)3C CF2)] [8].
  • Part One Interchange of Monohapto- and Pentahaptocyclopentadienyl Rings in Early Transition Metal Metallocene Systems

    Part One Interchange of Monohapto- and Pentahaptocyclopentadienyl Rings in Early Transition Metal Metallocene Systems

    PART ONE INTERCHANGE OF MONOHAPTO- AND PENTAHAPTOCYCLOPENTADIENYL RINGS IN EARLY TRANSITION METAL METALLOCENE SYSTEMS PART TWO A NEW ROUTE TO PREPARING POLYMER-ATTACHED METALLOCENE DERIVATIVES PART THREE GYGLOPENTADIENYL LIGAND EXCHANGE REACTIONS IN SELECTED SYSTEMS Thesis for the Degree of Ph. D. MICHIGAN STATE UNIVERSITY , JOHN GOO-SHUH LE ‘2," 5, 1977 .I:\‘.' . 4| 41 IfIIIIsE:_1~.e;!cI—:;*:. -;I. um . HI u-‘\‘ ———w‘ 9471“) dcifi'ségé'dfiéIIWNxI:.‘vzv‘5“: LIBRARY II. Ecliigan Stan) University This is to certify that the thesis entitled (1) INTEROHANOE OF MONOHAPTO- AND PENTAHAPTO CYCLORENTADIENYL RINGS IN SOME EARLY TRANSITION METAL METALLOCENE SYSTEMS (2) A NEw ROUTE TO PREPARING POLYMER-ATTACHED METALLOCENE DERIVATIVES (3) CYCLOPENTADIENYL BRggNQ1§¥CHANGE REACTIONS IN SELECTED SYSTEMS John Guo-shuh Lee has been accepted towards fulfillment of the requirements for Ph. D. CHEMISTRY degree m Major professor Date 5190’?) 0-7 639 ABSTRACT PART ONE INTERCHANGE OF MONOHAPTO- AND PENTAHAPTOCYCLOPENTADIENYL RINGS IN SOME EARLY TRANSITION METAL METALLOCENE SYSTEMS PART TWO A NEW ROUTE TO PREPARING POLYMER-ATTACHED METALLOCENE DERIVATIVES PART THREE CYCLOPENTADIENYL LIGAND EXCHANGE REACTIONS IN SELECTED SYSTEMS BY John Guo—shuh Lee PART ONE PMR and mass spectral analysis have been used to study the inter- change of pentahapto-bonded cyclopentadienyl rings with monohapto-bonded cyclopentadienyl rings in the compounds (CSHS)4M (M - Ti, Zr, Hf, Nb, Ta, Mo, and W) and (C5H5)3V or monohapto-bonded benzylcyclopentadienyl rings in the compounds (C6H5CH205H4)(CSHS)2MC1 (M - Ti, Zr, Hf, Nb, Ta, Mo, and W). As soon as the CpaM (or CpBMCI) species are generated (in- dicated by a color change), the exchange occurs and the equilibrium is established.
  • Reactions of Alkyl and Alkenyl Zirconocene Complexes

    Reactions of Alkyl and Alkenyl Zirconocene Complexes

    Reactions of alkyl and alkenyl zirconocene complexes by Klark Thor Hanson A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Chemistry Montana State University © Copyright by Klark Thor Hanson (1992) Abstract: Zirconacycles have been. demonstrated to react sluggishly with acyl chlorides even at elevated temperatures . Studies were undertaken to detertmine whether or not this reaction could be facilitated via transmetallation of one or both of the carbon-zirconium bonds of the zirconacycle to a more suitable metal. This research demonstrates that zirconacycles will react with acyl chlorides in the presence of secondary metallic reagents. Cuprate reagents and catalytic palladium complexes have been demonstrated to function in this capacity, presumably via stoichiometric and catalytic transmetallation respectively. REACTIONS OF ALKYL AND ALKENYL ZIRCONOCENE COMPLEXES by Klark Thor Hanson A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Chemistry MONTANA STATE UNIVERSITY Bozeman, Montana April 1992 ii APPROVAL of a thesis submitted by Klark Thor Hanson This thesis has been read by each member of the thesis committee and has been found to be satisfactory regarding content, English usage, format, citations, bibliographic style, and consistency, and is ready for submission to the College of Graduate Studies. Date Chairperson/ Graduat Committee Approved for the Major Department ^ JC 0- ^ __ Date He$ra.\ Major Department O Approved for the College of Graduate Studies Date I ' Graduate? Dean iii STATEMENT OF PERMISSION TO USE In presenting this thesis in partial fulfillment of the requirements for a master's degree at Montana State University, I agree that the Library shall make it available to borrowers under the rules of the Library.
  • Syntheses, Crystal Structures and Enantioseparation 2

    Syntheses, Crystal Structures and Enantioseparation 2

    ansa-Metallocene derivatives XXXIX 1 Biphenyl-bridged metallocene complexes of titanium, zirconium, and vanadium: syntheses, crystal structures and enantioseparation 2 Monika E. Huttenloch, Birgit Dorer, Ursula Rief, Marc-Heinrich Prosenc, Katrin Schmidt, Hans H. Brintzinger * Fakultiitfiir Chemie. UniL'ersitiit KOl1stanz. Each M737. D-78457 Konstanz. Germany Abstract Chiral, biphenyl-bridged metallocene complexes of general type biph(3,4-R2CsH2)2MCI2 (biph = 1,1'-biphenyldiyI) were synthesized and characterized. For the dimethyl-substituted titanocenes and zirconocenes (R CH 3; M Ti, Zr). preparations with increafed overall yields and an optical resolution method were developed. The bis(2-tetrahydroindenyI) complexes (R,R = (CH2)4; M = Ti, Zr) were obtained by an alternative synthetic route and characterized with regard to their crystal structures. Syntheses of the phenyl-substituted derivatives (R C 6 H 5; M Ti, Zr) and of a chiral, methyl-substituted vanadocene complex (R CH 3; M V) are also reported. Keywords: Titanium; Zirconium; Vanadium; Metallocene; Enantioseparation 1. Introduction Me2Si(2-SiMe14-IBuCsH)2-metallocenes of Y, Sc, Ti, and Zr [10]. Jordan and coworkers recently developed a Ever since meso and racemic ansa-titanocene iso­ powerful method for the syntheses of rac-C 2 H i l-inde­ mers were first characterized by Huttner and coworkers nyl)2 Zr(NMez)2 and rac-SiMe2(I -indenyI)2 Zr(NMe 2)2 [1], the formation of these diastereomers and their sepa­ in high yields, which is based on equilibration of rac ration has been a continuing challenge in metallocene and meso products by the amine eliminated in the chemistry (for a review see Ref.