DOCSLIB.ORG

Aryl‑NHC Group 13 Trimethyl Complexes : Structural, Stability and Bonding Insights

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Aryl‑NHC Group 13 Trimethyl Complexes : Structural, Stability and Bonding Insights This document is downloaded from DR‑NTU (https://dr.ntu.edu.sg) Nanyang Technological University, Singapore. Aryl‑NHC group 13 trimethyl complexes : structural, stability and bonding insights Wu, Melissa Meiyi 2017 Wu, M. M. (2017). Aryl‑NHC group 13 trimethyl complexes : structural, stability and bonding insights. Doctoral thesis, Nanyang Technological University, Singapore. http://hdl.handle.net/10356/70204 https://doi.org/10.32657/10356/70204 Downloaded on 28 Sep 2021 13:14:06 SGT ATTENTION: The Singapore Copyright Act applies to the use of this document. Nanyang Technological University Library. NANYANG TECHNOLOGICAL UNIVERSITY DIVISION OF CHEMISTRY AND BIOLOGICAL CHEMISTRY SCHOOL OF PHYSICAL & MATHEMATICAL SCIENCES Aryl-NHC Group 13 Trimethyl Complexes: Structural, Stability and Bonding Insights Wu Meiyi Melissa G1102527F Supervisor: Asst Prof Felipe Garcia Contents Acknowledgements .............................................................................................................. iv Abbreviations ....................................................................................................................... v Abstract.............................................................................................................................. viii 1. Introduction 1.1. N-Heterocyclic Carbenes (NHC) ................................................................................. 1 1.1.1. Electronic Properties ............................................................................................ 1 1.1.2. Steric Properties ................................................................................................. 4 1.2. Group 13 Elements .................................................................................................... 6 1.3. Group 13 Metal Carbene Complexes ......................................................................... 6 1.3.1. Aluminium Carbene Complexes 1.3.1a AlH3•NHC ..................................................................................................... 7 1.3.1b AlMe3•NHC ................................................................................................... 9 1.3.1c AlR3•NHC ................................................................................................... 12 1.3.1d AlX3•NHC ................................................................................................... 15 1.3.1e AlXnH3-n•NHC (n = 1 or 2) ............................................................................ 15 1.3.1f Chelating NHC Al Complexes ...................................................................... 17 1.3.1. Gallium Carbene Complexes 1.3.1a GaH3•NHC, GaXnH3-n•NHC (n = 1 or 2) and GaHnR3-n•NHC (n = 0, 1) ......... 20 1.3.1b GaMe3•NHC and GaXnMe3-n•NHC (n = 1) .................................................... 22 1.3.1c GaX3•NHC .................................................................................................. 23 1.3.1d Chelating NHC Ga Complexes ................................................................... 28 1.3.1. Indium Carbene Complexes 1.3.1a InH3•NHC, InXnH3-n•NHC (n = 1 or 2) ........................................................... 29 1.3.1b InXnMe3-n•NHC (n = 1 or 2) .......................................................................... 30 1.3.1c InX3•NHC and Chelating NHC In halide complexes .................................... 31 1.3.1. Thallium Carbene Complexes .......................................................................... 37 2. Trimethylaluminium NHC Species Summary ........................................................................................................................ 38 2.1. Introduction .............................................................................................................. 39 2.2. Results and Discussion 2.2.1. Synthesis of Trimethylaluminium Complexes .................................................... 40 2.2.2. Spectroscopic Studies of Trimethylaluminium Complexes ................................ 41 2.2.3. Crystallographic Studies of Trimethylaluminium Complexes ............................. 42 2.2.4. Lewis acid-base Properties of Trimethylaluminium Complexes ........................ 44 2.2.5. Stability Studies of Trimethylaluminium Complexes .......................................... 46 i 2.2.6. By-product obtained from SIPr•AlMe3 (125) ...................................................... 52 2.2.7. Reactivity Studies on Complexes ..................................................................... 53 2.3. Conclusions ............................................................................................................. 60 3. Trimethylgallium and Indium NHC Species Summary ........................................................................................................................ 61 3.1. Introduction .............................................................................................................. 62 3.2. Results and Discussion 3.2.1. Synthesis of Trimethylgallium and Indium complexes ....................................... 63 3.2.2. Spectroscopic Studies of Trimethylgallium and Indium complexes ................... 64 3.2.3. Crystallographic studies of Trimethylgallium and Indium complexes ................. 64 3.2.4. Lewis acid-base properties of Trimethylgallium and Indium complexes ............ 68 3.2.5. Stability Studies of Trimethylgallium and Indium complexes ............................. 70 3.2.6. Bonding Studies of NHCs Group 13 Complexes ............................................... 73 3.2.7. By-product obtained from SIPr•InMe3 (152) ....................................................... 77 3.3. Conclusions ............................................................................................................. 79 4. Mechanochemical Methodologies in NHC Main Group Complexes Summary ........................................................................................................................ 80 4.1. Introduction .............................................................................................................. 81 4.2. Results and Discussion 4.2.1. Attempted solvent-based synthesis of Group 13 complexes ............................. 83 4.2.2. Mechanochemical synthesis of Group 13 complexes ....................................... 85 4.2.3. Spectroscopic studies of mechanochemical synthesized complexes ................ 86 4.2.4. Crystallographic studies of mechanochemical synthesized complexes ............. 87 4.3. Reversible reaction being observed through mechanochemical synthesis ............... 89 4.4. Synthesis of chelating Group 13 complexes utilising mechanochemistry ................. 90 4.5. Conclusions ............................................................................................................. 92 5. Experimental Section 5.1. Inert Atmosphere Techniques ................................................................................... 93 5.1.1. Vacuum and Schlenk Line ................................................................................. 93 5.1.2. Glovebox ........................................................................................................... 93 5.1.3. Starting Material and Solvent ............................................................................ 94 5.2. Analytical Instruments and Procedures ..................................................................... 94 5.2.1. NMR Spectroscopy ........................................................................................... 94 5.2.2. Melting Point Determination .............................................................................. 95 5.2.3. Infrared Spectroscopy ....................................................................................... 95 5.2.4. High-Resolution Mass Spectroscopy ................................................................. 95 ii 5.2.5. Single Crystal X-ray Diffraction Studies ............................................................. 95 5.3. Preparation of Starting Materials .............................................................................. 97 5.4. Synthesis of New Compounds 5.4.1. Synthesis of New Trimethylaluminium Compounds ......................................... 102 5.4.2. Synthesis of Trimethylaluminium By-products ................................................. 106 5.4.3. Synthesis of New Trimethylgallium Compounds .............................................. 111 5.4.4. Synthesis of New Trimethylindium Compounds .............................................. 115 5.4.5. Synthesis of Trimethylindium By-product ......................................................... 119 5.5. Mechanochemical Synthesis of Compounds 5.5.1. Synthesis of IMes→MCl3 .................................................................................. 121 5.5.2. Synthesis of Bidentate Ligands for Mechanochemical Synthesis .................... 124 6. References.................................................................................................................. 126 7. Appendices Appendix 1 %VBur and Topographic Steric Maps ........................................................ 132 Appendix 2 Solid State Structures for New Compounds ............................................. 140 Appendix 3 Structures of Labelled Compounds .......................................................... 148 iii Acknowledgements First and foremost, I will like to thank my boss, Dr Felipe García, for his relentless
Load more

Recommended publications
  • Deposition Chemical Selection Guide
    SPECIALTY CHEMICALS AND ENGINEERED MATERIALS Deposition Chemical Selection Guide DEPOSITION PRECURSORS — Inter-metal dielectric precursors High-k gate and capacitor precursors TEOS Tetraethylorthosilicate HfCl4 Hafnium tetrachloride (standard and UHP grade) 4MS Tetramethylsilane ZrCl4 Zirconium tetrachloride OMCTS Octamethylcyclotetrasiloxane AlCl3 Aluminium trichloride NxTi Ti dopant CVD dopants Precursors for alternative high-k dielectrics and dopants* TEB Triethylborate TEMAZ Tetrakis(ethylmethylamido)zirconium(IV) TEPO Triethylphosphate TMB Trimethylborate Metallization including barrier materials TMP Trimethylphosphite HP CCTBA* High Purity dicolbalt hexacarbonyl tert- butylacetylene Silicon oxide and nitride precursors TDMAT Tetrakis-dimethylamino Titanium BDEAS Bis (diethylamino)silane TiCl4 Titanium tetrachloride BDMAMS bis(dimethylamino) methylsilane WCl6 Tungsten hexachloride SiNCH* Entegris proprietary WCl5 Tungsten pentachloride HMDS Hexamethyldisilane Joppa27™ (In collaboration with AMAT) HCDS Hexachlorodisilane Precursors for cobalt (selective or non-selective)* C H N Pyridine 5 5 TBTEMT (Tert-butylimido)tris(ethylmethylamido)tantalum(V) H O UHP grade water 2 Other metal precursors (eg. Ru, Y, Er, Mg, Al, Sn, W, Ir) Precursors for low temperature Si oxides and nitrides* TMDSO Tetramethyldisiloxane *Currently available at sampling volumes. Scale up to higher volume production would be available, depending on demand. Other precursors SiCl4 Silicon tetrachloride PZT cocktails Lead zirconate titanate ™ PH3 Phosphine in SAGE packaging
    [Show full text]
  • Advances-In-Inorganic-Chemistry-50
    Advances in INORGANIC CHEMISTRY Volume 50 ADVISORY BOARD I. Bertini J. Reedijk Universita´ degli Studi di Firenze Leiden University Florence, Italy Leiden, The Netherlands A. H. Cowley P. J. Sadler University of Edinburgh University of Texas Edinburgh, Scotland Austin, Texas, USA A. M. Sargeson H. B. Gray The Australian National University California Institute of Technology Canberrs, Australia Pasadena, California, USA Y. Sasaki M. L. H. Green Hokkaido University University of Oxford Sapporo, Japan Oxford, United Kingdom D. F. Shriver O. Kahn Northwestern University Evanston, Illinois, USA Institut de Chimie de la Matie`re Condense´e de Bordeaux Pessac, France R. van Eldik Universita¨t Erlangen-Nu¨mberg Andre´E. Merbach Erlangen, Germany Institut de Chimie Mine ´rale et Analytique K. Wieghardt Universite´ de Lausanne Max-Planck Institut Lausanne, Switzerland Mu¨lheim, Germany Advances in INORGANIC CHEMISTRY Main Group Chemistry EDITED BY A. G. Sykes Department of Chemistry The University of Newcastle Newcastle upon Tyne United Kingdom CO-EDITED BY Alan H. Cowley Department of Chemistry and Biochemistry The University of Texas at Austin Austin, Texas VOLUME 50 San Diego San Francisco New York Boston London Sydney Tokyo This book is printed on acid-free paper. ᭺ȍ Copyright 2000 by ACADEMIC PRESS All Rights Reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the Publisher. The appearance of the code at the bottom of the first page of a chapter in this book indicates the Publisher’s consent that copies of the chapter may be made for personal or internal use of specific clients.
    [Show full text]
  • Indium(III) Chloride – Catalyzed Michael Addition of Thiols to Chalcones : a Remarkable Solvent Effect
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Publications of the IAS Fellows Issue in Honor of Dr. Rama Rao ARKIVOC 2005 (iii) 44-50 Indium(III) chloride – catalyzed Michael addition of thiols to chalcones : a remarkable solvent effect Brindaban C. Ranu,* Suvendu S. Dey, and Sampak Samanta Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Calcutta – 700 032, India E-mail: [email protected] Dedicated to Dr. A. V. Rama Rao on the occasion of his 70th birthday (received 28 Aug 04; accepted 23 Sep 04; published on the web 26 Sep 04) Abstract Indium(III) chloride in methanol efficiently catalyzes Michael addition of aromatic and aliphatic thiols to chalcones and related compounds. This reaction is remarkably solvent selective and it does not proceed in conventional solvents such as tetrahydrofuran, methylene chloride and water. Keywords: Michael addition, thiol, chalcone, indium(III) chloride, solvent effect Introduction The Michael addition of thiols to electron deficient alkenes is a very useful process for making carbon-sulfur bond. This addition to chalcone derivatives is very interesting and challenging as it is less facile compared to the addition to aliphatic acyclic enones and thus it is not always satisfactory with the conventional reagents used for general 1,4-addition. Recently, a number of 1a procedures involving a variety of catalysts such as synthetic diphosphate Na2CaP2O7, natural 1b 1c 1d phosphate, InBr3, fluorapatite, have been reported. Indium halides, particularly indium(III) chloride have emerged as a potent Lewis acid for various organic transformations in recent times.2 As a part of our interest in indium(III) chloride 3 catalyzed reactions we discovered that although InCl3 has been used in the Michael addition of silylenol ethers,4a amines,4b pyrroles4c and indoles4d to electron-deficient alkenes no report has been found demonstrating the use of InCl3 for addition of thiols to chalcones and related systems.
    [Show full text]
  • Download (7Mb)
    A Thesis Submitted for the Degree of PhD at the University of Warwick Permanent WRAP URL: http://wrap.warwick.ac.uk/90802 Copyright and reuse: This thesis is made available online and is protected by original copyright. Please scroll down to view the document itself. Please refer to the repository record for this item for information to help you to cite it. Our policy information is available from the repository home page. For more information, please contact the WRAP Team at: [email protected] warwick.ac.uk/lib-publications Reactions and Co-ordination Chemistry of Indium Trialkyls and Trihalides. Ian Alan Degnan A thesis submitted for the degree of Doctor of Philosophy. University of Warwick, Department of Chemistry. Septem ber 1989 To Mam and Dad -for making this possible. Contents. Page. Chapter 1: Introduction. Group 13 Elements. 4 Co-ordination Chemistry of the Indium Trihalides. 9 Mono-Complexes of Indium Trihalides. 10 Bis-Complexes of Indium Trihalides. 12 Tris-Complexes of Indium Trihalides. 17 Unusual Indium Trihalide Complexes. 20 Phosphine Complexes of Indium Triiodide. 22 Metathetical Reactions of Indium Trihalides. 30 Organometallic Derivatives of Indium. 33 Organoindium Halides. 33 Organoindium Compounds. 37 Reactions of Organoindium Compounds. 39 Control of Oligomerisation in Indium Compounds. 55 Chapter 2. Phosphine Complexes of Indium Trihalides. 58 Introduction. 59 Mono-Phosphine Complexes of Indium Triiodide. 60 X-ray Diffraction Study of InCI3(PMe3)2. 83 Indium Triiodide Complexes of Diphos. 86 Chapter 3. Metathetical Reactions of Indium Trihalides. 94 Introduction. 95 Reaction of Indium Triiodide Phosphine Complexes with Methyllithium. 96 Reaction of Indium Triiodide Triphenylphosphine Complex with Methyllithium.
    [Show full text]
  • Thermochemical Modelling and Experimental Validation of in Situ Indium Volatilization by Released Halides During Pyrolysis of Smartphone Displays
    metals Article Thermochemical Modelling and Experimental Validation of In Situ Indium Volatilization by Released Halides during Pyrolysis of Smartphone Displays Benedikt Flerus 1,2,*, Thomas Swiontek 1, Katrin Bokelmann 2, Rudolf Stauber 2 and Bernd Friedrich 1 1 Institute of Process Metallurgy and Metal Recycling IME, RWTH Aachen University, Intzestraße 3, 52056 Aachen, Germany; [email protected] (T.S.); [email protected] (B.F.) 2 Project Group, Materials Recycling and Resource Strategies IWKS, Fraunhofer Institute for Silicate Research ISC, Brentanostraße 2, 63755 Alzenau, Germany; [email protected] (K.B.); [email protected] (R.S.) * Correspondence: bfl[email protected]; Tel.: +49-(0)241-80-95856 Received: 22 November 2018; Accepted: 5 December 2018; Published: 8 December 2018 Abstract: The present study focuses on the pyrolysis of discarded smartphone displays in order to investigate if a halogenation and volatilization of indium is possible without a supplementary halogenation agent. After the conduction of several pyrolysis experiments it was found that the indium evaporation is highly temperature-dependent. At temperatures of 750 ◦C or higher the indium concentration in the pyrolysis residue was pushed below the detection limit of 20 ppm, which proved that a complete indium volatilization by using only the halides originating from the plastic fraction of the displays is possible. A continuous analysis of the pyrolysis gas via FTIR showed that the amounts of HBr, HCl and CO increase strongly at elevated temperatures. The subsequent thermodynamic consideration by means of FactSage confirmed the synergetic effect of CO on the halogenation of indium oxide. Furthermore, HBr is predicted to be a stronger halogenation agent compared to HCl.
    [Show full text]
  • Stabilization and Reactivity of Low Oxidation State Indium Compounds
    University of Windsor Scholarship at UWindsor Electronic Theses and Dissertations Theses, Dissertations, and Major Papers 2013 Stabilization and Reactivity of Low Oxidation State Indium Compounds Christopher Allan University of Windsor Follow this and additional works at: https://scholar.uwindsor.ca/etd Recommended Citation Allan, Christopher, "Stabilization and Reactivity of Low Oxidation State Indium Compounds" (2013). Electronic Theses and Dissertations. 4939. https://scholar.uwindsor.ca/etd/4939 This online database contains the full-text of PhD dissertations and Masters’ theses of University of Windsor students from 1954 forward. These documents are made available for personal study and research purposes only, in accordance with the Canadian Copyright Act and the Creative Commons license—CC BY-NC-ND (Attribution, Non-Commercial, No Derivative Works). Under this license, works must always be attributed to the copyright holder (original author), cannot be used for any commercial purposes, and may not be altered. Any other use would require the permission of the copyright holder. Students may inquire about withdrawing their dissertation and/or thesis from this database. For additional inquiries, please contact the repository administrator via email ([email protected]) or by telephone at 519-253-3000ext. 3208. STABILIZATION AND REACTIVITY OF LOW OXIDATION STATE INDIUM COMPOUNDS By Christopher J. Allan A Dissertation Submitted to the Faculty of Graduate Studies Through Chemistry and Biochemistry In Partial Fulfillment of the Requirements for The Degree of Doctor of Philosophy at the University of Windsor Windsor, Ontario, Canada 2013 ©2013 Christopher J. Allan Declaration of Co-Authorship / Previous Publications I. Declaration of Co-Authorship This thesis incorporates the outcome of joint research undertaken in collaboration with Hugh Cowley under the supervision of Jeremy Rawson.
    [Show full text]
  • Adduct Purification of Trimethylgallium Using 4-Dimethylaminopyridine
    International Journal of Advanced Science and Technology Vol. 41, April, 2012 Adduct Purification of Trimethylgallium using 4-Dimethylaminopyridine Selvakumar Dhanasingh1*, Rajendra Singh2 and Mohammed Nasim3 1Defence BioEngineering and Electromedical laboratory, C. V. Raman Nagar, Bangalore – 560 093, India 2Directorate of ER & IPR, DRDO Bhawan, Rajaji Marg, New Delhi – 110105, India 3Defence Materials & Stores Research and Development Establishment, DMSRDE P.O., G.T. Road, Kanpur – 208 013, India [email protected] Abstract 1:1 and 2:1 adducts of trimethylgallium (TMGa) with 4-dimethylaminopyridine (DMAP) were synthesized and characterized by 1H, 13C NMR, FAB-MS and Trace elemental analyses using ICP-MS. Both adducts are non-pyrophoric, thermally dissociable and easy to handle. FAB-MS study suggests that the adducts are associated in tetrameric forms. TMGa of purity more than 99.999% (5N) was released from these adducts, which shows the adducts are potential candidates to produce high pure metal alkyl sources for Metal-Organic Chemical Vapor Deposition (MOCVD). Keywords: Trimethylgallium, pyrophoric, MOCVD precursor, adduct purification technique 1. Introduction The electronic properties of II-VI and III-V compound semiconducting thin films deposited by MOCVD method are mainly determined by the purity of the precursors [1, 2]. As most of the metal alkyls for MOCVD are volatile and highly reactive pyrophoric liquids, the physical purification methods such as, fractional distillation and low temperature crystallization are difficult to employ and often large amount of metal alkyls need to be discarded to obtain them with high purity. However, these metal alkyls can be purified by ‘adduct purification technique’, which involves the formation of adducts between the metal alkyl with an appropriate Lewis base, which are easy to handle and can be purified by re- crystallization [3, 4, 5].
    [Show full text]
  • Abstract Book
    Monday Afternoon, June 29, 2020 to be developed with atomic-scale level of controllability, including uniformity and selectivity. In this talk, atomic layer etching (ALE) of Cu and Atomic Layer Etching Ni, for their intended application in BOEL and EUV are presented. Room Baekeland - Session ALE1-MoA The unique aspect of this ALE process is the combined effect of directional chemical ions and isotropic reactive neutrals. Specifically, ALE of Ni and Cu ALE of Metals and Alloys thin film is realized using sequential surface modification by directional Moderators: Heeyeop Chae, Sungkyunkwan University (SKKU), Alfredo plasma oxidation and removal of the modified surface layer by isotropic gas Mameli, TNO/Holst Center phase formic acid exposure. Both blanket and patterned samples were 1:30pm ALE1-MoA-1 Mechanistic Insights into Thermal Dry Atomic Layer studied using this reaction scheme. A etch rate of 3 to 5 nm/cycle is determined from the blanket samples, and final features with sidewall Etching of Metals and Alloys, Andrew Teplyakov, University of Delaware angle of 87 is obtained on patterned samples. The effectiveness of the INVITED approach is chemically confirmed by the measuring the increase and The mechanisms of thermally induced reactions of atomic layer deposition decrease of the signals of metal oxide peaks using XPS. Etched thickness (ALD) and atomic layer etching (ALE) can be in sometimes viewed as and final feature geometry are determined by SEM and TEM. proceeding in opposite directions. However, for atomic layer processing of metals, that would mean that the best designed and most efficient reaction With proper chemistries and experimental conditions, this thermal-plasma pathways leading to metal deposition would produce insurmountable ALE is capable of delivering highly selective and anisotropic patterning of energy barriers for a reverse process to occur spontaneously.
    [Show full text]
  • Trimethylaluminium - Wikipedia, the Free Encyclopedia Page 1 of 3
    Trimethylaluminium - Wikipedia, the free encyclopedia Page 1 of 3 Trimethylaluminium From Wikipedia, the free encyclopedia (Redirected from Trimethylaluminum) Trimethylaluminium is the chemical compound with Trimethylaluminium the formula Al2(CH3)6, abbreviated as Al2Me6, (AlMe3)2 or the abbreviation TMA. This pyrophoric, colorless liquid is an industrially important organoaluminium compound. It evolves white smoke (aluminium oxides) when the vapor is released into the air. IUPAC name Contents trimethylalumane Other names ■ 1 Structure and bonding Trimethylaluminium; aluminium trimethyl ■ 2 Synthesis and applications Identifiers ■ 3 Semiconductor grade TMA CAS number 75-24-1 ■ 4 References PubChem 16682925 ■ 5 External links ChemSpider 10606585 SMILES C[Al](C)C Structure and bonding InChI InChI=1S/3CH3.Al/h3*1H3; Al2Me6 exists as a dimer, analogous in structure and Key: JLTRXTDYQLMHGR-UHFFFAOYSA-N bonding to diborane. As with diborane, the metalloids are connected by a 3-center-2-electron bond: the InChI=1/3CH3.Al/h3*1H3;/rC3H9Al/c1-4(2)3/h1- shared methyl groups bridge between the two 3H3 aluminium atoms. The Al-C(terminal) and Al-C Key: JLTRXTDYQLMHGR-MZZUXTGEAJ (bridging) distances are 1.97 and 2.14 Å, respectively. Properties [1] The carbon atoms of the bridging methyl groups Molecular formula C6H18Al2 are each surrounded by five neighbors: three Molar mass 144.18 g/mol hydrogen atoms and two aluminium atoms. The Appearance Colorless liquid methyl groups interchange readily intramolecularly Density 0.752 g/mL and intermolecularly. Melting point 15 °C 3-Centered-2-electron bonds are an utterance of "electron-deficient" molecules and tend to reactions Boiling point with Lewis bases that would give products consisting 125 °C of 2-centered-2-electron bonds.
    [Show full text]
  • The First Hydrides of Boron
    UNIVERSIDADE DE LISBOA FACULDADE DE CIÊNCIAS SECÇÃO AUTÓNOMA DE HISTÓRIA E FILOSOFIA DAS CIÊNCIAS UNDER THE CARBON SPELL: DIBORANE’S PUZZLING STRUCTURE AND THE EMERGENGE OF BORON CHEMISTRY Nuno Manuel Castanheira de Figueiredo Dissertação orientada pela Professora Doutora Ana Simões, da Secção Autónoma de Filosofia e História das Ciências da Faculdade de Ciências da Universidade de Lisboa. MESTRADO EM HISTÓRIA E FILOSOFIA DAS CIÊNCIAS 2011 Resumo Este trabalho apresenta o primeiro estudo sistemático da história da química dos boranos, compostos de boro e hidrogénio cujas estruturas e natureza das ligações químicas desafiaram de forma irredutível a teoria da ligação química até aos anos cinquenta do século XX. Actualmente, a química do boro é um dos mais promissores ramos da química, com um vasto leque de aplicações às indústrias química e farmacéutica, à nano-tecnologia e à medicina. Neste último ramo, destacam-se as aplicações na luta contra o cancro e no desenvolvimento de medicamentos com um elevado grau de especificidade e inovação. Num futuro próximo, espera-se que a química do boro seja capaz de operar uma verdadeira revolução social, posicionando-se como uma poderosa alternativa à química do carbono que será capaz de oferecer todo um novo mundo de aplicações inéditas. Estas são o resultado da fascinante capacidade do átomo de boro para se ligar de formas surpreendentes e formar complexas estruturas que se baseiam em compostos de boro e hidrogénio (boranos). A grande apetência do boro para se ligar ao oxigénio impede que os boranos existam na natureza. A grande susceptibilidade destes à acção da humidade e do ar torna-os especialmente instáveis e difíceis de manusear e preservar.
    [Show full text]
  • Filament-Activated Chemical Vapour Deposition of Nitride Thin Films
    ADVANCED MATERIALS FOR OPTICS AND ELECTRONICS, VOL 6,135-146 (1996) Review Paper Filament-activated Chemical Vapour Deposition of Nitride Thin Films Sadanand V. Deshpande,* Jeffrey L. Dupuiet and Erdogan Gulari* Department of Chemical Engineering and Center for Display Technology and Manufacturing, The University of Michigan, Ann Arbor, MI 48109, U.S.A. We have applied the novel method of hot filament-activated chemical vapour deposition (HFCVD) for low-temperature deposition of a variety of nitride thin films. In this paper the results from our recent work on aluminium, silicon and titanium nitride have been reviewed. In the HFCVD method a hot tungsten filament (1500-1850°C) was utilised to decompose ammonia in order to deposit nitride films at low substrate temperatures and high rates. The substrate temperatures ranged from 245 to 600°C. The film properties were characterised by a number of analytical and optical methods. The effect of various deposition conditions on film properties was studied. All the films obtained were of high chemical purity and had very low cr no detectable tungsten contamination from the filament metal. KEYWORDS hot filament chemical vapour deposition; CVD; high-rate deposition; ammonia: silicon nitride: aluminium nitride: titanium nitride INTRODUCTION design and operating regimes, films with varied properties can be deposited with little or no COP- tamination from reactions at the reactor walls as is Hot filament-activated chemical vapour deposition found in other techniques such as plasma-assisted (HFCVD) is a simple and a relatively inexpensive chemical vapour deposition. method that has been used to deposit a variety of HFCVD has been extensively used for over a materials.
    [Show full text]
  • The Allure of Aluminium
    in your element The allure of aluminium Daniel Rabinovich outlines the history, properties and uses of aluminium — one of the most versatile, pervasive and inexpensive metals today, yet it was considered a rare and costly element only 150 years ago. t is hard to believe that aluminium was silver, which hampered the development a common Lewis acid, is extensively applied once more expensive than gold and that, of large-scale applications and motivated in Friedel–Crafts acylation and alkylation Iin the mid-nineteenth century, Napoleon the search for an alternative and more reactions, and aluminium chlorohydrate, III used silverware made of the light metal economical preparation process. Al2Cl(OH)5, is the active ingredient in when he really wanted to impress his guests It was only in 1886 that Charles M. Hall many antiperspirants. Large quantities at stately dinners. Even though element 13 in the US and Paul L. T. Héroult in France, of methylaluminoxane, a generic name is the most abundant metal in the Earth’s almost simultaneously and completely used to describe the ill-defined mixture of crust (~8%) and is present in more than independently, devised aluminium species obtained by partial hydrolysis of 270 different minerals, its high affinity for production processes that relied on the trimethylaluminium, are employed in the oxygen and the chemical stability of its electrolysis of alumina (Al2O3) dissolved Ziegler–Natta polymerization of olefins. oxides and silicates precluded its isolation in molten cryolite (Na3AlF6). An efficient The
    [Show full text]