DOCSLIB.ORG

This Thesis Has Been Submitted in Fulfilment of the Requirements for a Postgraduate Degree (E.G

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
This Thesis Has Been Submitted in Fulfilment of the Requirements for a Postgraduate Degree (E.G This thesis has been submitted in fulfilment of the requirements for a postgraduate degree (e.g. PhD, MPhil, DClinPsychol) at the University of Edinburgh. Please note the following terms and conditions of use: • This work is protected by copyright and other intellectual property rights, which are retained by the thesis author, unless otherwise stated. • A copy can be downloaded for personal non-commercial research or study, without prior permission or charge. • This thesis cannot be reproduced or quoted extensively from without first obtaining permission in writing from the author. • The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the author. • When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given. Transition-Metal-Hydrogen Systems at Extreme Conditions I V N E R U S E I T H Y T O H F G E R D I N B U Thomas Scheler A thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the University of Edinburgh March 2013 Abstract The application of extreme conditions offers a general route for the synthesis of materials under equilibrium conditions. By finely tuning the thermodynamic variables of pressure and temperature one can manipulate matter on an atomic scale, creating novel compounds or changing the properties of existing materials. In particular, the study of hydrogen and hydrogen compounds has attracted the attention of researchers in the past. Although hydrogen readily reacts with many elements at ambient conditions, there is a significant “hydride gap” covering the d-metals between the Cr-group and Cu-group elements. At elevated pressures however, the chemical potential of hydrogen rises steeply. At sufficient pressures, hydrogen overcomes the dissociation barrier at the metal surface and atomic hydrogen diffuses into the metal, usually occupying interstitial sites in the host matrix. These interstitial hydrogen alloys can exhibit interesting physical properties, such as modified crystalline structures, different compressibility, altered microstructure (nanocrystallinity), hydrogen mediated superconductivity or potential hydrogen storage capabilities. Furthermore, theory predicts that hydrogen confined in a host matrix might undergo the elusive transition to a metallic groundstate at considerably lower pressures than pure hydrogen. Most d-metals have been found to exhibit hydride phases at extended conditions of pressure and temperature. However, besides rhenium, the 6th row metals between tungsten and gold, as well as silver, have not or only very recently been found to form bulk hydrides. In the course of this PhD-thesis, several of the missing metal- hydrides were successfully synthesized in the diamond anvil cell and characterized by in-situ x-ray diffraction using synchrotron radiation. i Declaration Except where otherwise stated, the research undertaken in this thesis was the unaided work of the author. Where the work was done in collaboration with others, a significant contribution was made by the author. T. Scheler March 2013 ii Acknowledgements In a way, writing these acknowledgements was the most difficult part of completing this thesis. So many people contributed to this work on various levels and it would be impossible to name you all. First and foremost, I would like to thank my supervisor Eugene Gregoryanz who has been a great mentor over the past few years and was always available when I needed help. Although it is difficult for me now to drink a Radler (Alster) without feeling a tiny amount of guilt. I would like to thank my colleagues Christophe Guillaume, Ross Howie, Phil Simpson and Donna Morton who helped a lot with the preparation of diamond anvil cells and with experiments during beamtimes. The memory of all of us sitting in the Dreyer in Hamburg is still fresh. A big Thank You also goes to everyone who was involved in the hydride projects: Miriam Marqu´es, who did calculations for the platinum and iridium projects, Yanming Ma and his group for calculations in the tungsten project, Christian Donnerer who took over the copper project and brought it to a nice conclusion, Zuzana Konˆopkov´a who spent several nights alone at the beamline at PETRA-III laser-heating our iridium samples, Olga Degtyareva for teaching me the basics of crystallographic data analysis, Thomas Cornelius and Tobias Sch¨ulli for giving me a few days of their inhouse beamtime at the ESRF for testing in-situ scanning x- ray diffraction microscopy. Additionally, there were so many people in CSEC who contributed with helpful discussions, by looking over data with me or simply during fantastic lunchtime conversations. Thank you Graham, Ingo, John, Emma, Craig, Mungo, Wanaruk, Chris, Rachel, Julian, Michal, Lucy, Alex. Looking back over the past three years, I would have never managed to get anywhere without the help of Jane Patterson. I would also like to extend my thanks to everyone in the CM-DTC, in particular Prof. Andy Mackenzie, Dr. Chris Hooley, Christine Edwards and Dr. Julie Massey and also Prof. Malcolm McMahon, who made it possible for me in the first place to come to Edinburgh. I am grateful to my examiners Prof. Paul Attfield and Dr. Michael Hanfland for their time and for providing constructive criticism which helped to improve this thesis significantly. Finally, the biggest (and I mean that) Thank You goes to Mirjam - for simply everything. iii Contents Abstract i Declaration ii Acknowledgements iii Contents iv List of figures v List of tables xiii 1 Introduction 1 1.1IntroductionandMotivation..................... 1 1.2 Thesis Outline ............................. 5 2 The Metal-Hydrogen System 9 2.1PropertiesofFreeHydrogen..................... 9 2.2HydrogeninHostMatrices...................... 13 2.3TransitionMetal-Hydrides:AReview................ 19 3 Review of High-Pressure Equipment and Techniques 31 3.1TheDiamondAnvilCell....................... 31 3.2 Pressure Scales ............................ 34 3.2.1 The Ruby Pressure Scale ................... 35 3.2.2 Equations of State as Pressure Scales ............ 37 3.2.3 TheDiamondRamanGauge................. 38 3.2.4 TheHydrogenVibronGauge................ 40 3.3 X-ray Diffraction at High Pressures ................. 41 3.3.1 BasicDiffractionTheory................... 42 3.3.2 In-situ Synchrotron X-ray Diffraction at High Pressure . 46 3.3.3 Determination of Hydrogen Content with X-rays ...... 48 3.4 Other Techniques . ......................... 50 3.4.1 RamanSpectroscopy..................... 50 iv CONTENTS 3.4.2 NeutronDiffraction...................... 50 3.4.3 TransmissionElectronMicroscopy.............. 51 3.4.4 FocusedIonBeams...................... 51 4 Transition Metal-Hydrogen Systems at Extreme Conditions 54 4.1Platinum................................ 54 4.2 Rhenium ................................ 64 4.3Tungsten................................ 73 4.4 Iridium ................................. 90 4.5Copper................................. 104 4.6Othermetals............................. 106 4.6.1 Gold.............................. 106 4.6.2 Silver .............................. 109 4.6.3 Osmium ............................ 110 5 Conclusions and Future Prospects 112 A Data Tables 116 Bibliography 130 Publications 143 v List of Figures 2.1 Raman spectrum of hydrogen at ∼5 GPa (fluid state) in a diamond anvil cell. The peaks denoted D1 and D2 are first and second order diamond Raman peaks (see chapter 3.2). The hydrogen rotons are seen at Raman shifts below D1 (So(1) and So(3)belongtootho-, So(0) and So(2) to para-hydrogen), the main hydrogen vibron mode −1 ν1 at shifts above 4000 cm .DatacourtesyofR.Howie...... 10 2.2 PT-Phase-diagram of hydrogen (see [Howie 12] and references therein (annexed to this thesis)). The thick solid line denotes the proposed melting curve. Coloured dashed lines with open triangles and crosses are theoretical transition boundaries between the molecular and atomic state. Thin solid lines are established phase boundaries between solid phases I, II and III. Thin dashed lines are the recently proposed phase boundaries including phase IV. 13 2.3 The Cr-group to Cu-group elements and their reactions with hydrogen (arrows). α denotes a bcc configuration, an hcp and γ an fcc configuration. Fully green fields denote the formation of a stoichiometric hydride. Ruthenium is only known to form a substoichiometric hydride with low hydrogen content, while no hydride phases are known for silver and osmium. The existence of a hydride phase in gold is in dispute (see chapter 2.3). The blue frame indicates the scope of the present work, i.e. elements investigated during the course of this thesis. For comparison, the state of knowledge prior to this work is included next to the respectivesymbols........................... 15 3.1 A) Schematic drawing of a typical DAC. B) Photograph of a closed symmetric DAC (“doughnut” type). C) Close-up schematic of the sample confined between the gasket (drawing) and the two diamondanvils............................. 32 vi LIST OF FIGURES 3.2 Gasket Preparation: A) A sheet of Re is placed between the aligned diamonds. B) The diamonds are pressed into the metal to create an indent. C) A centered hole is drilled into the indent. D) The metal sample is placed with a sharp needle in the hole. E) The cell is closed with one diamond leaving a small gap. F) Air in the cell is replaced with hydrogen gas and the cell is closed. G)-H) Optical micrograph of the sample hole taken through the diamonds. The metal sample and a ruby-sphere can be seen in the 50 μmhole. 34 3.3 A) Energy levels in the Cr3+ ion, taken from [Syassen 08]. B) Fluorescence spectrum from ruby showing the R1 and R2 lines. 36 3.4 Equations of state for the metals listed in Table 3.1 (see there for references). Inset shows EoS for copper. .............. 38 3.5 Equation of state of hydrogen. Inset shows d-spacings of hydrogen Bragg peaks vs. pressure. The values are derived from the EoS given in [Loubeyre 96]. For practical purposes, the data can be foundinTableA.1........................... 39 3.6 The Akahama pressure scale for the diamond Raman edge [Akahama 07]. InsetshowstheobservedRamanspectrumat123GPa......
Load more

Recommended publications
  • Formation of Superhexagonal Chromium Hydride by Exposure of Chromium Thin Film to High Temperature, High Pressure Hydrogen in a Ballistic Compressor
    Portland State University PDXScholar Dissertations and Theses Dissertations and Theses 1991 Formation of Superhexagonal Chromium Hydride by Exposure of Chromium Thin Film to High Temperature, High Pressure Hydrogen in a Ballistic Compressor Yi Pan Portland State University Follow this and additional works at: https://pdxscholar.library.pdx.edu/open_access_etds Let us know how access to this document benefits ou.y Recommended Citation Pan, Yi, "Formation of Superhexagonal Chromium Hydride by Exposure of Chromium Thin Film to High Temperature, High Pressure Hydrogen in a Ballistic Compressor" (1991). Dissertations and Theses. Paper 1243. https://doi.org/10.15760/etd.1242 This Dissertation is brought to you for free and open access. It has been accepted for inclusion in Dissertations and Theses by an authorized administrator of PDXScholar. Please contact us if we can make this document more accessible: [email protected]. FORMATION OF surPERHEXAGONAL CHROMIUM HYDRIDE BY EXPOSURE OF CHIW~[IUM THIN !FILM TO HIGH TEMPERATURE, HIGH PRESSURE: l![YDROGEN IN A BALLISTIC COMPRESSOR by YI PAN A dissertation submitted inlpartial fulfillment of the requirement for the degree of DOCTOR OF PHILOSOPHY in ENVIRONMENT}\L I SCIENCES I AND RESOURCES: PHYSICS Portland State University 1991 TO THE OFFICE OF GRADUATE STUDIES: The memlbers of the Committee approve the dissertation of Yi Pan presented in June 27, 1991. Donald Howard odegom APPROVED: C. William Savery, Vice Provost(/for Graduate Studies and Researclil AN ABSTRACT OF THE DISSERTATION OF Yi Pan for
    [Show full text]
  • Binuclear Copper(I) Borohydride Complex Containing Bridging Bis
    crystals Article Binuclear Copper(I) Borohydride Complex Containing Bridging Bis(diphenylphosphino) Methane Ligands: Polymorphic Structures of 2 [(µ2-dppm)2Cu2(η -BH4)2] Dichloromethane Solvate Natalia V. Belkova 1 ID , Igor E. Golub 1,2 ID , Evgenii I. Gutsul 1, Konstantin A. Lyssenko 1, Alexander S. Peregudov 1, Viktor D. Makhaev 3, Oleg A. Filippov 1 ID , Lina M. Epstein 1, Andrea Rossin 4 ID , Maurizio Peruzzini 4 and Elena S. Shubina 1,* ID 1 A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences (INEOS RAS), 119991 Moscow, Russia; [email protected] (N.V.B.); [email protected] (I.E.G.); [email protected] (E.I.G.); [email protected] (K.A.L.); [email protected] (A.S.P.); [email protected] (O.A.F.); [email protected] (L.M.E.) 2 Inorganic Chemistry Department, Peoples’ Friendship University of Russia (RUDN University), 117198 Moscow, Russia 3 Institute of Problems of Chemical Physics, Russian Academy of Sciences (IPCP RAS), 142432 Moscow, Russia; [email protected] 4 Istituto di Chimica dei Composti Organometallici Consiglio Nazionale delle Ricerche (ICCOM CNR), 50019 Sesto Fiorentino, Italy; [email protected] (A.R.); [email protected] (M.P.) * Correspondence: [email protected]; Tel.: +7-495-135-5085 Academic Editor: Sławomir J. Grabowski Received: 18 September 2017; Accepted: 17 October 2017; Published: 20 October 2017 Abstract: Bis(diphenylphosphino)methane copper(I) tetrahydroborate was synthesized by ligands exchange in bis(triphenylphosphine) copper(I) tetrahydroborate, and characterized by XRD, FTIR, NMR spectroscopy. According to XRD the title compound has dimeric structure, [(µ2-dppm)2Cu2(η2-BH4)2], and crystallizes as CH2Cl2 solvate in two polymorphic forms (orthorhombic, 1, and monoclinic, 2) The details of molecular geometry and the crystal-packing pattern in polymorphs were studied.
    [Show full text]
  • Cuh-Catalyzed Enantioselective Alkylation of Indole Derivatives with Ligand-Controlled Regiodivergence
    CuH-Catalyzed Enantioselective Alkylation of Indole Derivatives with Ligand-Controlled Regiodivergence The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Ye, Yuxuan et al. "CuH-Catalyzed Enantioselective Alkylation of Indole Derivatives with Ligand-Controlled Regiodivergence." Journal of the American Chemical Society 141, 9 (January 2019): 3901–3909 © 2019 American Chemical Society As Published http://dx.doi.org/10.1021/jacs.8b11838 Publisher American Chemical Society (ACS) Version Author's final manuscript Citable link https://hdl.handle.net/1721.1/126070 Terms of Use Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. HHS Public Access Author manuscript Author ManuscriptAuthor Manuscript Author J Am Chem Manuscript Author Soc. Author Manuscript Author manuscript; available in PMC 2020 March 06. Published in final edited form as: J Am Chem Soc. 2019 March 06; 141(9): 3901–3909. doi:10.1021/jacs.8b11838. CuH-Catalyzed Enantioselective Alkylation of Indole Derivatives with Ligand-Controlled Regiodivergence Yuxuan Ye1, Seoung-Tae Kim2,3, Jinhoon Jeong2,3, Mu-Hyun Baik2,3,*, and Stephen L. Buchwald1,* 1Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, United States 2Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea 3Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon, 34141, Republic of Korea Abstract Enantioenriched molecules bearing indole-substituted stereocenters form a class of privileged compounds in biological, medicinal, and organic chemistry.
    [Show full text]
  • Copper Hydride Catalyzed Hydroamination of Alkenes and Alkynes
    Copper Hydride Catalyzed Hydroamination of Alkenes and Alkynes The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Pirnot, Michael T., Yi-Ming Wang, and Stephen L. Buchwald. “Copper Hydride Catalyzed Hydroamination of Alkenes and Alkynes.” Angewandte Chemie International Edition 55.1 (2016): 48–57. As Published http://dx.doi.org/10.1002/anie.201507594 Publisher Wiley Blackwell Version Author's final manuscript Citable link http://hdl.handle.net/1721.1/110464 Terms of Use Creative Commons Attribution-Noncommercial-Share Alike Detailed Terms http://creativecommons.org/licenses/by-nc-sa/4.0/ HHS Public Access Author manuscript Author Manuscript Author ManuscriptAngew Chem Author Manuscript Int Ed Engl Author Manuscript . Author manuscript; available in PMC 2016 March 08. Published in final edited form as: Angew Chem Int Ed Engl. 2016 January 4; 55(1): 48–57. doi:10.1002/anie.201507594. Copper Hydride-Catalyzed Hydroamination of Alkenes and Alkynes Dr. Michael T. Pirnot†, Dr. Yi-Ming Wang†, and Prof. Dr. Stephen L. Buchwald Department of Chemistry, Massachusetts Institute of Technology 77 Massachusetts Avenue, Cambridge, MA 02139 (USA) Stephen L. Buchwald: [email protected] Abstract Over the past few years, CuH-catalyzed hydroamination has been discovered and developed as a robust and conceptually novel approach for the synthesis of enantioenriched secondary and tertiary amines. The success in this area of research was made possible through the large body of precedent in copper(I) hydride catalysis and the well-explored use of hydroxylamine esters as electrophilic amine sources in related copper-catalyzed processes.
    [Show full text]
  • Sop Pyrophoric 2 12/16/2019
    Owner DOC. NO. REV. DATE C.H.O SOP PYROPHORIC 2 12/16/2019 DOC. TITLE SOP FOR PYROPHORIC CHEMICALS Environmental Health & Safety STANDARD OPERATING PROCEDURES (SOP) FOR WORKING WITH PYROPHORIC CHEMICALS AT AMHERST COLLEGE ___________________________________________________________________ General Information Pyrophoric Chemicals are solid, liquid, or gas compounds that, when exposed to air or moisture at or below 54°C (130°F), can spontaneously ignite. Examples of Pyrophoric chemicals used at Amherst College Laboratories include: sodium hydride, zinc powder, and Grignard reagents. See the “Appendix” page below for a full list of Pyrophoric Chemicals. Pyrophoric chemicals are often used as catalysts in chemical reactions or as reducing and deprotonating agents in organic chemistry. Note that Pyrophoric chemicals may also be characterized by other hazards, hence, users of these chemicals may also need to refer to other SOPs that cover other hazards. In addition, each individual chemical’s Safety Data Sheet (SDS) should be consulted before they are used. _____________________________________________________________________________________ Personal Protective Equipment When working with Pyrophoric Chemicals, the following personal protective equipment (PPE) must be worn, at a minimum. Depending on the specific chemical, other forms of protection might be required. Consult the SDS for each chemical before use: Splash goggles Lab coat (Fire resistant lab coat highly recommended) Long pants Close toed shoes Gloves – Nitrile gloves adequate for accidental contact with small quantities. However, the use of fire resistant Nomex/ Leather Pilot’s gloves is highly recommended _____________________________________________________________________________________ Safety Devices All work with Pyrophoric chemicals must be done in a glove box, vacuum manifold, or any enclosed inert environment. If work must be done in a fume hood, ensure that the hood sash is in the lowest feasible position.
    [Show full text]
  • A Dimeric Hydride-Bridged Complex with Geometrically Distinct Iron Centers Giving Rise to an S = 3 Ground State Anne K
    Article Cite This: J. Am. Chem. Soc. 2019, 141, 11970−11975 pubs.acs.org/JACS A Dimeric Hydride-Bridged Complex with Geometrically Distinct Iron Centers Giving Rise to an S = 3 Ground State Anne K. Hickey,† Samuel M. Greer,|,§ Juan A. Valdez-Moreira,† Sean A. Lutz,† Maren Pink,† Jordan A. DeGayner,‡ T. David Harris,‡ Stephen Hill,|,∧ Joshua Telser,∥ and Jeremy M. Smith*,† † Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States | National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States § ∧ Department of Chemistry & Biochemistry and Department of Physics, Florida State University, Tallahassee, Florida 32306, United States ‡ Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States ∥ Department of Biological, Physical and Health Sciences, Roosevelt University, Chicago, Illinois 60605, United States *S Supporting Information :44:57 (UTC). ABSTRACT: Structural and spectroscopic characterization of the dimeric iron t hydride complex [Ph2B( BuIm)2FeH]2 reveals an unusual structure in which a tetrahedral iron(II) site (S = 2) is connected to a square planar iron(II) site (S =1) by two bridging hydride ligands. Magnetic susceptibility reveals strong ferromagnetic coupling between iron centers, with a coupling constant of J = −1 o legitimately share published articles. +110(12) cm , to give an S = 3 ground state. High-frequency and -field electron paramagnetic resonance (HFEPR) spectroscopy confirms this model. A qualitative molecular orbital analysis of the electronic structure, as supported by electronic structure calculations, reveals that the observed spin configuration results from the orthogonal alignment of two geometrically distinct four-coordinate iron fragments held together by highly covalent hydride ligands.
    [Show full text]
  • ( 12 ) United States Patent
    US010450388B2 (12 ) United States Patent (10 ) Patent No. : US 10 ,450 , 388 B2 Duchateau et al. (45 ) Date of Patent: Oct . 22, 2019 6 , 028 , 151 A 2 / 2000 Wasserman et al . ( 54 ) PROCESS FOR THE PREPARATION OF A 6 , 248 ,837 B1 6 /2001 Chung et al. BRANCHED POLYOLEFIN 6 , 258 , 902 B1 7 /2001 Campbell, Jr . et al. 2008 /0311812 A1 * 12/ 2008 Arriola CO8F 10 / 00 (71 ) Applicant: SABIC GLOBAL TECHNOLOGIES 442 /327 B . V . , Bergen op Zoom (NL ) 2009 /0048399 AL 2 /2009 Reijntjens et al . 2014 / 0039138 A1 2 /2014 Giesbrecht et al. 2014 / 0039139 A1 2 / 2014 Giesbrecht et al . (72 ) Inventors: Robbert R . Duchateau , Eindhoven 2014 /0039140 A1 2 /2014 Giesbrecht et al. (NL ) ; Miloud Bouyahyi , Eindhoven 2014 /0055250 A12 /2014 Speegle et al . (NL ) ; Lidia Jasinska - Walc , Eindhoven 2014 /0350200 A1 11 /2014 Baintas - Geurts et al . (NL ) ; Martin Alexander Zuideveld , Kelmis (BE ) FOREIGN PATENT DOCUMENTS (73 ) Assignee : SABIC GLOBAL TECHNOLOGIES EP 1092730 A14 / 2001 EP 1283222 A1 2 / 2003 B . V . , Bergen op Zoom (NL ) EP 1605000 AL 12 / 2005 WO 9319104 AL 9 / 1993 ( * ) Notice : Subject to any disclaimer , the term of this WO 9613529 A15 / 1996 patent is extended or adjusted under 35 WO 9632427 Al 10 / 1996 U . S . C . 154 (b ) by 0 days . WO 9742232 A1 11/ 1997 WO 9742236 AL 11 / 1997 (21 ) Appl. No. : 15 /537 , 926 WO 0043426 Al 7 / 2000 WO 0123441 A1 4 / 2001 WO 03014046 A1 2 / 2003 (22 ) PCT Filed : Dec . 23 , 2015 Wo 2004081064 AL 9 / 2004 wo 2007134851 AL 11 / 2007 ( 86 ) PCT No .
    [Show full text]
  • The Selective Oligomerization of Ethylene Using Chromium Diphosphine Catalysts
    The Selective Oligomerization of Ethylene Using Chromium Diphosphine Catalysts and The Synthesis and Reactivity of Group 7 Carbonyl Derivatives Relevant to Synthesis Gas Conversion Thesis by Paul Richard Elowe In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena, California 2009 (Defended July 17, 2008) 2009 Paul Richard Elowe All Rights Reserved ii Dédiée à ma famille, and to An iii Acknowledgments Spending the last five years of my life at Caltech has been quite an experience. When my undergraduate advisor Donald Berry told me that graduate studies at Caltech are unique, I could not realize how true that was at the time. There have been many good moments, and surely many challenging ones as well. I went from being John Bercaw’s academic grandson to his son in a matter of a few months in the summer of 2003. John has allowed me from the very beginning to work on the projects I was most interested in. His hands-off approach was instrumental in my rapid development as a chemist over the last few years. Thank you for everything you have brought me all these years. I also want to acknowledge Jay Labinger for his guidance. Always available, Jay answered many questions and helped out whenever I was stuck on a problem. I truly enjoyed playing tennis with you. I should also thank my thesis committee, Harry Gray, David Tirrell, and Jacqueline Barton, for great advice during candidacy, as well as throughout the proposals and thesis exams.
    [Show full text]
  • Phase Transformations, Crystal and Magnetic Structures of High-Pressure Hydrides of D-Metals V.E
    L Journal of Alloys and Compounds 330±332 (2002) 110±116 www.elsevier.com/locate/jallcom Phase transformations, crystal and magnetic structures of high-pressure hydrides of d-metals V.E. Antonov* Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow District, Russia Abstract This paper will brie¯y discuss the high-pressure-hydrogen techniques used at the Institute of Solid State Physics, Russian Academy of Sciences, the T±P diagrams of the studied binary metal±hydrogen systems and the crystal and magnetic structures of high-pressure hydrides formed in those systems. A compilation of the available experimental data and a list of relevant publications are provided for reference purposes. 2002 Elsevier Science B.V. All rights reserved. Keywords: Metal hydrides; Crystal structure; Magnetic properties 1. Introduction copper when the temperature is raised and forms Cu±Ga alloys of increasing thermal stability as its concentration in Most transition metals form hydrides at suf®ciently high the copper matrix decreases. Te¯on, Cu and Ga are largely pressures of hydrogen. The technique for compressing impermeable to hydrogen. The dead space in the copper gaseous hydrogen to pressures of up to 9 GPa at tempera- capsule is ®lled with kaolin wool which does not react tures up to 5008C [1], and recently to 10008C [2], with H2 , Cu and d-metals in the T±P range of interest. developed at the Institute of Solid State Physics, Russian Due to the hardness of its ®bres, the wool remains porous Academy of Sciences (ISSP RAS), made it possible to even at high pressures, leaving enough room for the synthesise hydrides of all 3d-metals and of all 4d-metals hydrogen gas inside the capsule and ensuring good access except Ru.
    [Show full text]
  • Metal Clusters History
    METAL CLUSTER BY DR. SHEERIN MASROOR For M.Sc Sem (II) Clusters in Chemistry • These are assembly of atoms or molecules which are intermediate in size between a molecule and a bulk solid. • The can be made up of diverse in stoichiometry. (Mingos and Wales 1990, Introduction to Cluster Chemistry) • Examples: Fullerene, Diborane. Metal Cluster • These are compounds that contain metal-metal bonds. • A compound that contains a group of two or more atoms where direct and substantial metal bonding is present. (Huheey Inorganic Chemistry Huheey, JE,Harper and Row, New York) • Examples: Co2(CO)8, Rh2(OAc)4, Stryker’s reagent(Osborn Complex). Dicobalt octacarbonyl Rhodium(II) acetate hexameric copper hydride ligatedwith triphenylphosphi ne Metal Clusters History • 12th century - Historically Metal cluster was calomel (Hg2Cl2). • 1826 - First polyoxometallate discovered was ammonium 3− phosphomolybdate, containing the PMo12O 40 anion, discovered by Berzelius. • 1908 - Miolatti-Rosenheim explained about the structure of 12- molybdophosphoric acid as a polyoxometalate cluster. • 1928 - Linus Pauling suggested structure that accurately accounts for structure of polyoxotungstate anion. • 1934 - J. F. Keggin obtains first crystal structure of polyoxo- metallate. Now known as Keggin stucture. • 1953 - X-Ray Evidence for Metal-to-Metal Bonds in Cupric and Chromous Acetate. -2 • 1964 - F. A. Cotton (Wilkinson Student) discovers Re2Cl8 which was having metal-metal bond. • Early 1960s - Cotton coins terms cluster when referring to chemical entities that contain one or more metal-metal bond. Preparation of Metal Clusters • Hydrothermal Synthesis • Crystallization of substances from high temperature conditions. • Generally reactions are carried in aqueous media which run in steel pressure vessels in an autoclave.
    [Show full text]
  • A Theoretical Study of Cr/Oxide Catalysts for Dehydrogenation of Short Alkanes
    A Theoretical Study of Cr/oxide Catalysts for Dehydrogenation of Short Alkanes Sindre Lillehaug Department of Chemistry University of Bergen 2006 Dissertation submitted for the degree of doctor scientiarum Jeg skjønner alt for mye og ingenting Og hjernen min sier pling pling pling a aLars Lillo-Stenberg Preface Natural gas reserves are being produced at increasing rates world wide, thus providing an abundance of short-alkane feedstock for the petrochemical industry. Effective routes to selective activation of short alkanes may represent a bottleneck of this development. In this respect, processes of catalytic dehydrogenation have significant economic potential. Several catalysts have been investigated and some are implemented industrially. At the core of one such catalyst are species of chromium oxide supported on the surface of amor- phous alumina. Since the original report by Frey and Huppke in 1933, this system has been under study, the literature expanding with the development of experimental meth- ods. However, due to the heterogeneity of the Cr/alumina surfaces a structure-activity relationship has not been determined to date. Opinions are converging regarding the ox- idation state of active chromium, but little is known about the nano-range surroundings of the active site. The involvement of oxygen ligands is a popular issue related to the mechanism of catalysis. Other remaining questions concern the chromium nuclearity of the active surface site and the role of the oxide support. With the development of quantum chemical tools and powerful hardware, computa- tional modelling emerges as a manageable complement to experiment. The combination may lead to novel insight into the structure-activity relationship on Cr/oxide surfaces.
    [Show full text]
  • Using Alcohols As Simple H2-Equivalents for Copper-Catalysed Transfer Semihydrogenations of Cite This: Chem
    ChemComm View Article Online COMMUNICATION View Journal | View Issue Using alcohols as simple H2-equivalents for copper-catalysed transfer semihydrogenations of Cite this: Chem. Commun., 2019, 55,13410 alkynes† Received 26th August 2019, Accepted 15th October 2019 Trinadh Kaicharla, Birte M. Zimmermann, Martin Oestreich and Johannes F. Teichert * DOI: 10.1039/c9cc06637c rsc.li/chemcomm Copper(I)/N-heterocyclic carbene complexes enable a transfer copper hydride-based catalytic transformation, namely the semi- semihydrogenation of alkynes employing simple and readily available reduction of internal alkynes to alkenes.10–12 alcohols such as isopropanol. The practical overall protocol circumvents The alkyne semihydrogenation poses challenges in stereo- theuseofcommonlyemployedhighpressureequipmentwhenusing selectivity (E vs. Z) and chemoselectivity (overreduction of the 10 Creative Commons Attribution 3.0 Unported Licence. dihydrogen (H2) on the one hand, and avoids the generation of stoichio- formed alkene to the corresponding alkane, Scheme 1), and thus metric silicon-based waste on the other hand, when hydrosilanes are serves as an ideal model reaction for catalyst development. To probe used as terminal reductants. a possible transfer of a hydrogen atom from the a-position of an alcohol by means of a copper(I) catalyst, we investigated the transfer Catalytic transfer hydrogenations (TH) are attractive for the semihydrogenation of internal alkyne 1,usinga,a-dideuterated reduction of a variety of functional groups, as they offer practical benzyl alcohol (2-d2, Scheme 1). Employing readily available [SIMes- protocols circumventing the need for high pressure equipment.1 CuCl]13 in catalytic amounts (10 mol%) and NaOtBu as base, full In general, for catalytic TH there is a need for easy-to-use and safe conversion either with microwave or conventional heating to the dihydrogen (H2) sources, as these reactants are associated with the corresponding alkene 3 was found.
    [Show full text]