DOCSLIB.ORG

UNIVERSITY of CALGARY Heterocyclic Cyclopentadienyl

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
UNIVERSITY of CALGARY Heterocyclic Cyclopentadienyl UNIVERSITY OF CALGARY Heterocyclic Cyclopentadienyl Analogs with BN Frameworks by Hanh Vien Ly A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMISTRY CALGARY, ALBERTA DECEMBER, 2007 © Hanh Vien Ly 2007 ISBN: 978-0-494-38226-4 Abstract The heterocyclic cyclopentadienyl analogs have provided a fertile area of research, owing to the interest in tuning the electronic properties of cyclopentadienyl (Cp) ligands for the development of more efficient catalysts and new materials. A variety of five-membered heterocyclic Cp analogs have been synthesized by the formal replacement of ring carbon atoms with isoelectronic main group fragments. Metal complexes containing these heterocyclic ligands have proven to be feasible ancillary ligands in catalysis. The primary objective of this thesis is the development of a novel class of heterocyclic Cp ligands having ring carbon fragments (CR) formally substituted with isolobal boron (BR−) and nitrogen (NR’+) fragments. The synthesis and characterization of the 1,2-diaza-3,5-diborolyl ligands with cyclic CB2N2 frameworks is described and their coordination to a variety of metal fragments is reported. Just like cyclopentadienyl, the 1,2-diaza-3,5-diborolyl ligands are excellent π ligands that exhibit interesting coordination properties. Alkali metal complexes of 1,2-diaza-3,5-diborolyls were synthesized and their investigation by single-crystal X-ray diffraction analysis revealed substantial coordinative similarities, but also remarkable differences in comparison to cyclopentadienyl ligands. Sandwich complexes containing these new heterocyclic π ligands were synthesized by metathesis reaction of the corresponding alkali metal salts with various metal halides. The structural characterization of a series of electron-rich group 12 and 14 metallocenes, as well as metallocenes of the early and late transition metals, revealed some unique coordinative properties of the ligands: η1, η3, η4 and η5- coordination modes of the 1,2-diaza-3,5-diborolyl ligands were observed, depending on ii the electron properties of the coordinated metals. In addition, the synthesis of the heterobicyclic 1,5-diaza-2,4,6,8-tetraborolyl ligand featuring a C2B4N2 framework is described and the structural investigation of its dipotassium salt showed that this heterobicyclic ligand is a promising π bridging linker for the construction of polydecker sandwich complexes. A triple-decker ruthenium sandwich complex featuring an unusual eight-membered C2B4N2 ring as the middle deck was synthesized through the insertion of two RuCp* fragments into the N-N bond of the heterobicyclic ligand. Electrochemical studies of the triple-decker ruthenocene are presented. The coordination chemistry of the 1,2,4-triaza-3,5-diborolyl ligand, a carbon-free heterocyclic Cp analog, was also investigated. The alkali metal salts of this ligand were synthesized via selective deprotonation of the ring nitrogen utilizing appropriate metalating agents. In contrast to the former ligands, the solid-state structures of the alkali metal complexes featuring these ligands are dominated by σ interactions of the ligand to the metal ions. A rhodium dimer containing 1,2,4-triaza-3,5-diborolyl ligands σ-bridging two Rh(cod) fragments was synthesized and characterized. The synthesis and characterization of a tricyclic compound with a B8N4 framework consisting of fused five- and six-membered rings was discussed, along with a study of its electrochemical properties. iii Acknowledgements I would like to thank my supervisor, Dr. Roland Roesler for his encouragement, enthusiasm and suggestions with respect to my graduate research. His instruction and trust in me have made me the chemist I am today. Special thanks to my PhD committee members, Dr. Tristram Chivers, Dr. Warren Piers, Dr. Richard Oakley, and Dr. Ray Turner. To all the past and present group members, Kelly, Matt, Taryn, Javier, Hongsui, Doaa and Andrea; I thank them for all the support and wonderful times that they have shared with me in and out of the lab. To my friends Bonnie and Vicky, thank you for the routine lunch calls and entertaining talks. All of these wonderful friendships are greatly cherished and I wish them all the best of luck in their future accomplishments. I would like to thank Dr. Masood Parvez, Dr. Dana Eisler, Dr. Jari Konu and Dr. Robert McDonald (University of Alberta) for their contribution and expertise with regard to X-ray crystallography. I would like to thank Dr. Heikki Tuononen for all the computational calculations, as well as Tracey Roemmele and Dr. René Boeré for their help with the EPR studies. I would also like to thank Dorothy Fox, Qiau Wu, Jian Jun Li, Roxanna Simank, Olivera Blagojevic and Dr. Raghav Yamdagni for their help and technical expertise. Special thank to Bonnie King for all of the administration work that she kept me (and Roland) on track and to Mark Toonen for his help with glassware. Most importantly, I would like to express my deepest gratitude to my parents, my grandma and my two sisters, Vien and Cindy, for their unconditional love, encouragement and endless support throughout this journey. I could not have done it without them. Thank you all. iv Table of Contents Abstract ............................................................................................................................... ii Acknowledgements ........................................................................................................... iiv List of Tables .................................................................................................................... iix List of Figures ................................................................................................................... xii List of Abbreviations ...................................................................................................... xvii List of Publications .......................................................................................................... xix CHAPTER ONE: Introduction ............................................................................................1 1.1 Cyclopentadienyl .....................................................................................................1 1.2. Heterocyclic Analogs of Cyclopentadienyl .............................................................4 1.2.1. General Considerations ................................................................................4 1.2.2. Cyclopentadienyl Analogs with C4E Frameworks .......................................5 1.2.3. Cyclopentadienyl Analogs with C5-nEn (n = 2 – 4) Frameworks ..................9 1.2.4. Carbon-Free Cyclopentadienyl Analogs with E5 Frameworks ..................21 1.2.5. Multidecker Sandwich Complexes of Boron-Containing Heterocycles ....24 1.3. Objectives and Outline of Thesis ...........................................................................25 CHAPTER TWO: 1,2-Diaza-3,5-diborolyl Ligands and their Alkali Metal Complexes ..28 2.1. Introduction ............................................................................................................28 2.2. Methodology for the Synthesis of 1,2-Diaza-3,5-diborolidines, their Spectroscopic Characterization and the X-ray Structures of 2.3c and 2.3d. .........30 2.3. Alkali Metal Salts Containing 1,2-Diaza-3,5-diborolyl Ligands (2.4 – 2.6). ........39 2.3.1. Synthesis and Spectroscopic Characterization of Alkali Metal Salts Incorporating the 1,2-Diaza-3,5-diborolyl Ligands (2.4a, 2.4b – 2.6b and 2.4c – 2.6c). .........................................................................................39 2.3.2. The X-ray Structures of Lithium (2.4a and 2.4c(thf)3), Sodium (2.5b, 2.5b(thf)3 and 2.5c(thf)3) and Potassium (2.6b(thf), 2.6b(thf)2 and v 2.6c(thf)) Complexes Incorporating the 1,2-Diaza-3,5-diborolyl Ligands. ......................................................................................................44 2.4. Synthesis and Spectroscopic Characterization of the Bicyclic 1,2-Diaza-3,5- diborolidine (2.3e) and their Alkali Metal Complexes (2.4e – 2.6e). ....................58 2.5. Conclusions ............................................................................................................61 CHAPTER THREE: Group 14 Metallocenes Incorporating 1,2-Diaza-3,5-diborolyl Ligands: Silicon, Germanium and Tin Complexes .........................63 3.1. Introduction ............................................................................................................63 3.2. Synthesis and Spectroscopic Characterization of the Trichlorosilyl-1,2-diaza- 3,5-diborolyl Complexes (3.1) and the X-ray Structure of 3.1b. ...........................66 3.3. Synthesis, Spectroscopic Characterization and X-ray Structure of Bis(1,2- diaza-3,5-diborolyl)germanium (3.2) and Bis(1,2-diaza-3,5-diborolyl)tin (3.3) Complexes..............................................................................................................70 3.4. Synthesis, Spectroscopic Characterization of Bis(1,2-diaza-3,5-diborolyl) chloromethyl tin chloride (3.4) and 1,2-Diaza-3,5-diborolyltin chloride (3.5) and the X-ray Structure of 3.4. ...............................................................................79 3.5. Synthesis and Spectroscopic Characterization of Cationic 1,2-Diaza-3,5- diborolyltin Borate Complexes (3.6). ....................................................................84 3.6. Conclusion .............................................................................................................86
Load more

Recommended publications
  • Nomination Background: Methylal (CASRN: 109-87-5)
    SUMMARY OF DATA FOR CHEMICAL SELECTION METHYLAL CAS NO. 109-87-5 BASIS OF NOMINATION TO THE CSWG The nomination of methylal to the CSWG is based on high production volume and exposure potential. Dr. Elizabeth Weisburger, a member of the American Conference of Governmental Industrial Hygienists (ACGIH) TLV Committee as well as the Chemical Selection Working Group (CSWG), provided a list of 281 chemical substances with ACGIH recommended TLVs for which there were no long term studies cited in the supporting data and no designations with respect to carcinogenicity. She presented the list to the Chemical Selection Planning Group (CSPG) for evaluation as chemicals which may warrant chronic testing: it was affirmed at the CSPG meeting held on August 9, 1994, that the 281 "TLV Chemicals" be reviewed as a Class Study. As a result of the class study review, methylal is presented as a candidate for testing by the National Toxicology Program because of: • potential for occupational exposures based on high production volume (1.2-64 million lbs) and estimate of worker exposure • evidence of occupational exposures based on TLV and other literature documentation • potential for general population exposures based on use as a solvent in consumer products and occurrence in environmental media • suspicion of carcinogenicity based on potential for metabolic release of formaldehyde and positive mutagenicity data • lack of chronic toxicity data. SELECTION STATUS ACTION BY CSWG : 9/25/96 Studies requested : - Carcinogenicity Priority : Moderate to High Rationale/Remarks : - Potential for human exposure - Inhalation route recommended for testing - Consider transgenic mouse model (p53 or TGAC) INPUT FROM GOVERNMENT AGENCIES/INDUSTRY Dr.
    [Show full text]
  • Clusters – Contemporary Insight in Structure and Bonding 174 Structure and Bonding
    Structure and Bonding 174 Series Editor: D.M.P. Mingos Stefanie Dehnen Editor Clusters – Contemporary Insight in Structure and Bonding 174 Structure and Bonding Series Editor: D.M.P. Mingos, Oxford, United Kingdom Editorial Board: X. Duan, Beijing, China L.H. Gade, Heidelberg, Germany Y. Lu, Urbana, IL, USA F. Neese, Mulheim€ an der Ruhr, Germany J.P. Pariente, Madrid, Spain S. Schneider, Gottingen,€ Germany D. Stalke, Go¨ttingen, Germany Aims and Scope Structure and Bonding is a publication which uniquely bridges the journal and book format. Organized into topical volumes, the series publishes in depth and critical reviews on all topics concerning structure and bonding. With over 50 years of history, the series has developed from covering theoretical methods for simple molecules to more complex systems. Topics addressed in the series now include the design and engineering of molecular solids such as molecular machines, surfaces, two dimensional materials, metal clusters and supramolecular species based either on complementary hydrogen bonding networks or metal coordination centers in metal-organic framework mate- rials (MOFs). Also of interest is the study of reaction coordinates of organometallic transformations and catalytic processes, and the electronic properties of metal ions involved in important biochemical enzymatic reactions. Volumes on physical and spectroscopic techniques used to provide insights into structural and bonding problems, as well as experimental studies associated with the development of bonding models, reactivity pathways and rates of chemical processes are also relevant for the series. Structure and Bonding is able to contribute to the challenges of communicating the enormous amount of data now produced in contemporary research by producing volumes which summarize important developments in selected areas of current interest and provide the conceptual framework necessary to use and interpret mega- databases.
    [Show full text]
  • Cyclopentyl Methyl Ether (CPME)
    Korean J. Chem. Eng., 34(2), 463-469 (2017) pISSN: 0256-1115 DOI: 10.1007/s11814-016-0265-5 eISSN: 1975-7220 INVITED REVIEW PAPER Measurement and correlation of the isothermal VLE data for the binary mixtures of cyclopentene (CPEN)+cyclopentyl methyl ether (CPME) Wan Ju Jeong and Jong Sung Lim† Department of Chemical and Biomolecular Engineering, Sogang University, C.P.O. Box 1142, Seoul 04107, Korea (Received 2 August 2016 • accepted 20 September 2016) Abstract−The isothermal vapor-liquid equilibrium data for the binary systems of cyclopentene (1)+cyclopentyl methyl ether (2) were measured at 313.15, 323.15, 333.15, 343.15 and 353.15 K using a dynamic-type equilibrium apparatus and online gas chromatography analysis. For all the measured VLE data consistency tests were performed for the verifi- cation of data using Barker’s method and the ASPEN PLUS Area Test method. All the resulting average absolute val- δ γ γ ues of residuals [ ln ( 1/ 2)] for Barker’s method and D values for the ASPEN PLUS area test method were com- paratively small. So, the VLE data reported in this study are considered to be acceptable. This binary system shows neg- ative deviation from Raoult’s law and does not exhibit azeotropic behavior at whole temperature ranges studied here. The measured data were correlated with the P-R EoS using the Wong-Sandler mixing rule. The overall average relative deviation of pressure (ARD-P (%)) between experimental and calculated values was 0.078% and that of vapor phase compositions (ARD-y (%)) was 0.452%. Keywords: Vapor Liquid Equilibria (VLE), Cyclopentyl Methyl Ether (CPME), Cyclopentene (CPEN), Peng-Robinson Equation of State (PR-EoS), Wong-Sandler Mixing Rule (WS-MR) INTRODUCTION however, have some disadvantages because they use dimethyl sul- fate and methyl iodide as a reactant, respectively, which are muta- Ethers are widely used in organic chemistry and biochemistry.
    [Show full text]
  • A Germaaluminocene†
    Chemical Science View Article Online EDGE ARTICLE View Journal | View Issue A germaaluminocene† Cite this: Chem. Sci., 2020, 11, 2982 Lena Albers, * Patrik Tholen, Marc Schmidtmann and Thomas Muller¨ * All publication charges for this article The reactions of dipotassium germacyclopentadienediide with two Group 13 dichlorides, Cp*BCl and have been paid for by the Royal Society 2 * ff of Chemistry Cp AlCl2, yield two structurally di erent products. In the case of boron a borole complex of germanium(II) is obtained. The aluminium halide gives an unprecedented neutral Received 21st January 2020 Accepted 7th February 2020 germaaluminocene. Both compounds were fully characterised by multinuclear NMR spectroscopy supported by DFT computations. The molecular structure of the germaaluminocene was DOI: 10.1039/d0sc00401d determined by XRD. rsc.li/chemical-science Introduction conversion and aer work-up complex 2c was isolated as a brown oil in 35% yield (Scheme 2). NMR spectroscopy evi- The aim of utilizing readily available and environmentally denced the presence of the expected borole ring with a h1- benign main group element compounds for activation of bound cyclopentadienyl substituent. Interestingly, the NMR Creative Commons Attribution-NonCommercial 3.0 Unported Licence. unreactive materials and strong bonds instead of transition data indicated frozen rotation around the B-Ca single bond, metal-based complexes became increasingly popular during the giving rise to ten 13C NMR signals for the cyclopentadienyl last decade.1 We attempted to follow this lead by establishing substituent (Table S3, ESI†). In addition, all four carbon atoms polarised heteroalkenes I as they mimic the electronic situation of the borole ring are magnetically non-equivalent.
    [Show full text]
  • The Reaction of Arenetricarbonylchromium Complexes with Alkyllithium Could Proceed Via a Variety of Pathways to Yield Any of Several Possible Products
    Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1975 The er action of arenetricarbonylchromium complexes with alkyllithium compounds Roger John Card Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Organic Chemistry Commons Recommended Citation Card, Roger John, "The er action of arenetricarbonylchromium complexes with alkyllithium compounds " (1975). Retrospective Theses and Dissertations. 5410. https://lib.dr.iastate.edu/rtd/5410 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. INFORMATION TO USERS This material was produced from a microfilm copy of the original document. While the most advance technological means to photograim and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted. The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction. 1. The sign or "target" for pages apparency lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adiacent pages. This may have necessitated cutting tiiru an image and duplicating adjscsnt pages to insure you complete continuity. 2. When an image on the film is obliterated with a large round biack mark, it is an indication Aat the photographer suspected that the copy may have moved during exposure and thus cause a blurred image.
    [Show full text]
  • Parallels to Frustrated Lewis/Radical Pair Chemistry
    klh00 | ACSJCA | JCA11.2.5208/W Library-x64 | manuscript.3f (R5.0.i3:5004 | 2.1) 2020/02/05 13:43:00 | PROD-WS-121 | rq_481292 | 7/01/2020 12:12:45 | 10 | JCA-DEFAULT pubs.acs.org/IC Article 1 Redox-Controlled Reactivity at Boron: Parallels to Frustrated Lewis/ 2 Radical Pair Chemistry ⊥ ⊥ 3 Anthony Wong, Jiaxiang Chu, Guang Wu, Joshua Telser, Roman Dobrovetsky, and Gabriel Menard́ * Cite This: https://dx.doi.org/10.1021/acs.inorgchem.0c01464 Read Online ACCESS Metrics & More Article Recommendations *sı Supporting Information 4 ABSTRACT: We report the synthesis of new Lewis-acidic boranes μ 5 tethered to redox-active vanadium centers, (Ph2N)3V( -N)B(C6F5)2 μ 6 (1a)and(N(CH2CH2N(C6F5))3)V( -N)B(C6F5)2 (1b). Redox IV/V 7 control of the V couple resulted in switchable borane versus 8 “hidden” boron radical reactivity, mimicking frustrated Lewis versus 9 frustrated radical pair (FLP/FRP) chemistry, respectively. Whereas V 10 heterolytic FLP-type addition reactions were observed with the V 11 complex (1b) in the presence of a bulky phosphine, homolytic peroxide, IV 12 or Sn−hydride, bond cleavage reactions were observed with the V * μ 13 complex, [CoCp2 ][(N(CH2CH2N(C6F5))3)V( -N)B(C6F5)2](3b), 14 indicative of boron radical anion character. The extent of radical 15 character was probed by spectroscopic and computational means. IV/V 16 Together, these results demonstrate that control of the V oxidation 17 states allows these compounds to access reactivity observed in both FLP 18 and FRP chemistry.
    [Show full text]
  • Pentamethylcyclopentadienyl Aminoborole Complexes of Hafnium
    Pentamethylcyclopentadienyl Aminoborole Complexes of Hafnium Thesis by Andrew F. Kiely In Partial Fufillment of the Requirements for the Degree of Doctor of Philosophy Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena, California 1997 (Submitted August 20,1996) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. For M y Parents Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. iii Acknowledgments First and most importantly, I would like to thank John Bercaw for the support, encouragement, and opportunities that he has given me over the course of my studies at Caltech. I have been very fortunate to have been able to learn chemistry from someone who is a fine and generous person as well as a great scientist, and I am very grateful to him. I am also grateful to Bill Schaefer, Larry Henling, and Mike Day for performing all the crystallographic work that is reported in this thesis. I appreciate all their good humor and patience despite my (occasional) impatience and (more occasional) ignorance. I've really enjoyed hiking with Bill and playing outfield with Larry as well. The students and post-docs in the Bercaw group have been friends as well as coworkers. Over the years, people in the Bercaw group have been generous with their time, advice and friendship. When I was getting started in the group, Donny Cotter, Bryan Coughlin, and Roger Quan were never too busy to answer my questions or to set me straight. I'm especially grateful to Roger, who helped me to learn vacuum line techniques when I was starting on the aminoborole project.
    [Show full text]
  • The Water-Energy Nexus: Challenges and Opportunities Overview
    U.S. Department of Energy The Water-Energy Nexus: Challenges and Opportunities JUNE 2014 THIS PAGE INTENTIONALLY BLANK Table of Contents Foreword ................................................................................................................................................................... i Acknowledgements ............................................................................................................................................. iii Executive Summary.............................................................................................................................................. v Chapter 1. Introduction ...................................................................................................................................... 1 1.1 Background ................................................................................................................................................. 1 1.2 DOE’s Motivation and Role .................................................................................................................... 3 1.3 The DOE Approach ................................................................................................................................... 4 1.4 Opportunities ............................................................................................................................................. 4 References ..........................................................................................................................................................
    [Show full text]
  • 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.
    [Show full text]
  • Neutral All Metal Aromatic Half-Sandwich Complexes Between Alkaline Earth and Transition Metals: an Ab-Initio Exploration
    Neutral All Metal Aromatic Half-Sandwich Complexes Between Alkaline Earth and Transition Metals: An Ab-initio Exploration Amlan Jyoti Kalita Cotton University Prem Prakash Sahu Cotton University Ritam Raj Borah Gauhati University Shahnaz Sultana Rohman Cotton University Chayanika Kashyap Cotton University Sabnam Swabaka Ullah Cotton University Indrani Baruah Cotton University Lakhya Jyoti Mazumder Cotton University Dimpul Konwar Gachon University Ankur Kanti Guha ( [email protected] ) Cotton University https://orcid.org/0000-0003-4370-8108 Research Article Keywords: Half-sandwich complexes, dual aromaticity, topological analyses Posted Date: May 24th, 2021 DOI: https://doi.org/10.21203/rs.3.rs-505446/v1 License: This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License Page 1/13 Version of Record: A version of this preprint was published at Structural Chemistry on July 7th, 2021. See the published version at https://doi.org/10.1007/s11224-021-01807-w. Page 2/13 Abstract Sandwich complexes nd their interests among the chemists after the breakthrough discovery of ferrocene. Since then, a number of sandwich and half sandwich complexes were predicted and synthesized. Herein, we have theoretically proposed a series of half-sandwich complexes involving a neutral Be3 ring and transition metal. Quantum chemical calculations have shown that the proposed complexes are quite stable involving high bond dissociation energies. The thermodynamics of their formation is also favorable. The Be3 ring in all cases posses dual aromaticity which has been ascertained based on magnetic as well as topological feature of electron density. Introduction Discovery of the rst sandwich complex (C5H5)2Fe, commonly known as “ferrocene”, drew the attention of the chemistry fraternity in no time [1–3].
    [Show full text]
  • Guidance Document Peroxide-Forming Chemicals
    Guidance Document Peroxide-Forming Chemicals Some chemicals can form peroxides under normal storage conditions. Some of the peroxide chemicals are unstable, especially when dried or concentrated, and can explode violently when subjected to heat, light or mechanical shock. In addition, some of the inadvertently formed peroxides can initiate other unexpected violent reactions (e.g. polymerizations) with other chemicals. When possible and practical for your work, purchase chemicals that have inhibitors added by the manufacturer. Label peroxide-forming chemicals with date received and date opened. Store peroxide-formers in airtight opaque containers with screw caps. Consider oxygen exclusion methods such as purging with inert gas or sealing containers with parafilm. Inspect containers for signs of peroxide formation. Do not open a container which has crystals or a visible cloudiness. Call EHS to come remove it. The friction caused by opening a lid can cause an explosion. Liquids can be tested for presence of peroxide. This is especially important prior to distilation. Most explosions of peroxide forming chemicals occur when a material is distilled to dryness. Peroxide test kits are available from chemical vendors. Contact EHS for additional guidance. Classification Table for Peroxide-Forming Chemicals Class I:: Unsaturated materials, especially those of low molecular weight, may polymerize violently and hazardously due to peroxide initiation. These chemicals can spontaneously decompose, becoming explosive after exposure to air with concentration. Discard unopened containers within 3 months. Opened containers should be tested for peroxides every 2 months. Acrylic acid Tetrafluoroethylene Acrylonitrile Vinyl acetate 1,3-Butadiene Vinyl acetylene Chlorobutadiene (chloroprene) Vinyl chloride Chlorotrifluoroethylene Vinyl pyridine Methyl methacrylate Vinylidiene chloride Styrene Class II: The following chemicals are a peroxide hazard upon concentration (distillation/evaporation).
    [Show full text]
  • Polyfluorene-Based Semiconductors Combined with Various Periodic
    Progress in Polymer Science 37 (2012) 1192–1264 Contents lists available at SciVerse ScienceDirect Progress in Polymer Science j ournal homepage: www.elsevier.com/locate/ppolysci Polyfluorene-based semiconductors combined with various periodic table elements for organic electronics ∗ Ling-Hai Xie, Cheng-Rong Yin, Wen-Yong Lai, Qu-Li Fan, Wei Huang Key Laboratory for Organic Electronics & Information Displays (KLOEID) and Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications (NUPT), Nanjing 210046, China a r t i c l e i n f o a b s t r a c t Article history: Polyfluorenes have emerged as versatile semiconducting materials with applications in Received 12 April 2011 various polymer optoelectronic devices, such as light-emitting devices, lasers, solar cells, Received in revised form 8 February 2012 memories, field-effect transistors and sensors. Organic syntheses and polymerizations Accepted 10 February 2012 allow for the powerful introduction of various periodic table elements and their build- Available online 16 February 2012 ing blocks into ␲-conjugated polymers to meet the requirements of organic devices. In this review, a soccer-team-like framework with 11 nodes is initially proposed to illus- Keywords: trate the structure–property relationships at three levels: chain structures, thin films ␲-Conjugated polymers and devices. Second, the modelling of hydrocarbon polyfluorenes (CPFs) is summarized Band-gap engineering Light-emitting diodes within the framework of a four-element design principle, in which we have highlighted Photovoltaic cell polymorphic poly(9,9-dialkylfluorene)s with unique supramolecular interactions, various Field-effect transistors hydrocarbon-based monomers with different electronic structures, functional bulky groups Memories with steric hindrance effects and ladder-type, kinked, hyperbranched and dendritic confor- mations.
    [Show full text]