The Chemistry of Carbene-Stabilized
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Review Sheet on Determining Term Symbols
Review Sheet on Determining Term Symbols Term symbols for electronic configurations are useful not only to the spectroscopist but also to the inorganic chemist interested in understanding electronic and magnetic properties of molecules. We will concentrate on the method of Douglas and McDaniel (p. 26ff); however, you may find other treatments equal or superior to the D & M method. Term symbols are a shorthand method used to describe the energy, angular momentum, and spin multiplicity of an atom in any particular state. The general form is a given as Tj where T is a capital letter corresponding to the value of L (the angular momentum quantum number) and may be assigned as S, P, D, F, G, … for |L| = 0, 1, 2, 3, 4, … respectively. The superscript “a” is called the spin multiplicity and can be evaluated as a = 2S +1 where S is the spin quantum number. The subscript “j” is the numerical value of J, a new quantum number defined as: J = l +S, which corresponds to the total orbital and spin angular momentum of the system. The term symbol 3P is read as triplet – Pee state and indicates that there are two unpaired electrons in a state with maximum orbital angular momentum, L=1. The number of microstates (N) of a system corresponds to the total number of distinct arrangements for “e” number of electrons to be placed in “n” number of possible orbital positions. N = # of microstates = n!/(e!(n-e)!) For a set of p orbitals n = 6 since there are 2 positions in each orbital. -
Fischer Carbene Complexes in Organic Synthesis Ke Chen 1/31/2007
Baran Group Meeting Fischer Carbene Complexes in Organic Synthesis Ke Chen 1/31/2007 Ernst Otto Fischer (1918 - ) Other Types of Stabilized Carbenes: German inorganic chemist. Born in Munich Schrock carbene, named after Richard R. Schrock, is nucleophilic on November 10, 1918. Studied at Munich at the carbene carbon atom in an unpaired triplet state. Technical University and spent his career there. Became director of the inorganic Comparision of Fisher Carbene and Schrock carbene: chemistry institute in 1964. In the 1960s, discovered a metal alkylidene and alkylidyne complexes, referred to as Fischer carbenes and Fischer carbynes. Shared the Nobel Prize in Chemistry with Geoffery Wilkinson in 1973, for the pioneering work on the chemistry of organometallic compounds. Schrock carbenes are found with: Representatives: high oxidation states Isolation of first transition-metal carbene complex: CH early transition metals Ti(IV), Ta(V) 2 non pi-acceptor ligands Cp2Ta CH N Me LiMe Me 2 2 non pi-donor substituents CH3 (CO) W CO (CO)5W 5 (CO)5W A.B. Charette J. Am. Chem. Soc. 2001, 123, 11829. OMe O E. O. Fischer, A. Maasbol, Angew. Chem. Int. Ed., 1964, 3, 580. Persistent carbenes, isolated as a crystalline solid by Anthony J. Arduengo in 1991, can exist in the singlet state or the triplet state. Representative Fischer Carbenes: W(CO) Cr(CO) 5 5 Fe(CO)4 Mn(CO)2(MeCp) Co(CO)3SnPh3 Me OMe Ph Ph Ph NEt2 Ph OTiCp2Cl Me OMe Foiled carbenes were defined as "systems where stabilization is Fischer carbenes are found with : obtained by the inception of the facile reaction which is foiled by the impossibility of attaining the final product geometry". -
States of Oxygen Liquid and Singlet Oxygen Photodynamic Therapy
Oxygen States of Oxygen As far as allotropes go, oxygen as an element is fairly uninteresting, with ozone (O3, closed-shell and C2v symmetric like SO2) and O2 being the stable molecular forms. Most of our attention today will be devoted to the O2 molecule that is so critically connected with life on Earth. 2 2 2 4 2 O2 has the following valence electron configuration: (1σg) (1σu) (2σg) (1πu) (1πg) . It is be- cause of the presence of only two electrons in the two π* orbitals labelled 1πg that oxygen is paramagnetic with a triplet (the spin multiplicity \triplet" is given by 2S+1; here S, the total spin quantum number, is 0.5 + 0.5 = 1). There are six possible ways to arrange the two electrons in the two degenerate π* orbitals. These different ways of arranging the electrons in the open shell are called \microstates". Further, because there are six microstates, we can say that the total degeneracy of the electronic states 2 3 − arising from (1πg) configuration must be equal to six. The ground state of O2 is labeled Σg , the left superscript 3 indicating that this is a triplet state. It is singly degenerate orbitally and triply degenerate in terms of spin multiplicity; the total degeneracy (three for the ground state) is given by the spin times the orbital degeneracy. 1 The first excited state of O2 is labeled ∆g, and this has a spin degeneracy of one and an orbital degeneracy of two for a total degeneracy of two. This state corresponds to spin pairing of the electrons in the same π* orbital. -
N-Heterocyclic Carbenes (Nhcs)
Baran Lab N - H e t e r o c y c l i c C a r b e n e s ( N H C s ) K. J. Eastman An Introduction to N-heterocyclic Carbenes: How viable is resonance contributer B? Prior to 1960, a school of thought that carbenes were too reactive to be smaller isolated thwarted widespread efforts to investigate carbene chemistry. base ! N N N N R R R R Perhaps true for the majority of carbenes, this proved to be an inaccurate X- assessment of the N-heterocyclic carbenes. H longer Kirmse, W. Angerw. Chem. Int. Ed. 2004, 43, 1767-1769 In the early 1960's Wanzlick (Angew. Chem. Int. Ed. 1962, 1, 75-80) first investigated the reactivity and stability of N-heterocyclic carbenes. Attractive Features of NHCs as Ligands for transition metal catalysts: Shortly thereafter, Wanzlick (Angew. Chem. Int. Ed. 1968, 7, 141-142) NHCs are electron-rich, neutral "#donor ligands (evidenced by IR frequency of reported the first application of NHCs as ligands for metal complexes. CO/metal/NHC complexes). Surprisingly, the field of of NHCs as ligands in transition metal chemistry Electron donating ability of NHCs span a very narrow range when compared to remained dormant for 23 years. phosphine ligands In 1991, a report by Arduengo and co-workers (J. Am. Chem. Soc. 1991, Electronics can be altered by changing the nature of the azole ring: 113, 361-363) on the extraodinary stability, isolation and storablility of benzimidazole<imidazole<imidazoline (order of electron donating power). crystalline NHC IAd. NHC-metal complex stability: NaH, DMSO, MeOH N N N N + H2 + NaCl NHCs form very strong bonds with the majority of metals (stronger than Cl- phosphines!) H IAd N-heterocyclic carbenes are electronically (orbital overlap) and sterically (Me vs. -
An Investigation of N-Heterocyclic Carbene Carboxylates
AN INVESTIGATION OF N-HETEROCYCLIC CARBENE CARBOXYLATES: INSIGHT INTO DECARBOXYLATION, A TRANSCARBOXYLATION REACTION, AND SYNTHESIS OF HYDROGEN BONDING PRECURSORS by Bret Ryan Van Ausdall A dissertation submitted to the faculty of The University of Utah in partial fulfillment of the requirement for the degree of Doctor of Philosophy Department of Chemistry The University of Utah May 2012 Copyright © Bret Ryan Van Ausdall 2012 All Rights Reserved The University of Utah Graduate School STATEMENT OF DISSERTATION APPROVAL The dissertation of Bret Ryan Van Ausdall has been approved by the following supervisory committee members: Janis Louie , Chair 7-8-2011 Date Approved Cynthia Burrows , Member 7-8-2011 Date Approved Thomas Richmond , Member 7-8-2011 Date Approved Matthew S. Sigman , Member 7-8-2011 Date Approved Debra Mascaro , Member 7-8-2011 Date Approved and by Henry S. White , Chair of the Department of Chemistry and by Charles A. Wight, Dean of The Graduate School. ABSTRACT A series of 1,3-disubstituted-2-imidazolium carboxylates, an adduct of CO2 and N-heterocyclic carbenes, was synthesized and characterized using single crystal X-ray, thermogravimetric, IR, and NMR analysis. The TGA analysis of the imidazolium carboxylates shows that as steric bulk on the N-substituent increases, the ability of the NHC-CO2 to decarboxylate increases. Single crystal X-ray analysis shows that the torsional angle of the carboxylate group and the C-CO2 bond length with respect to the imidazolium ring is dependent on the steric bulk of the N-substituent. Rotamers in the t unit cell of a single crystal of I BuPrCO2 (2f) indicate that the C-CO2 bond length increases as the N-substituents rotate toward the carboxylate moiety, which suggests that rotation of the N-substituents through the plane of the C-CO2 bond may be involved in the bond breaking event to release CO2. -
Photochemical and Magnetic Properties of Complex and Nuclear Chemistry
• Programme: MSc in Chemistry • Course Code: MSCHE2001C04 • Course Title: Photochemical and magnetic properties of complex and nuclear chemistry • Unit: Electronic spectra of coordination compounds • Course Coordinator: Dr. Jagannath Roy, Associate Professor, Department of Chemistry, Central University of South Bihar Note: These materials are only for classroom teaching purpose at Central University of South Bihar. All the data/figures/materials are taken from text books, e-books, research articles, wikipedia and other online resources. 1 Course Objectives: 1. To make students understand structure and propeties of inorganic compounds 2. To accuaint the students with the electronic spectroscopy of coordination compounds 3. To introduce the concepts of magnetochemistry among the students for analysing the properties of complexes. 4. To equip the students with necessary skills in photochemical reaction transition metal complexes 5. To develop knowledge among the students on nuclear and radio chemistry Learning Outcomes: After completion of the course, learners will be able to: 1. Analyze the optical/electronic spectra of coordination compounds 2. Make use of the photochemical behaviour of complexes in designing solar cells and other applications. 3. Design and perform photochemical reactions of transition metal complexes 4. Analyze the magnetic properties of complexes 5. Explain the various phenomena taking place in the nucleus 6. Understand the working of nuclear reactors 2 Lecture-1 Lecture Topic- Introduction to the Electronic Spectra of Transition Metal complexes 3 Crystal field theory (CFT) is ideal for d1 (d9) systems but tends to fail for the more common multi- electron systems. This is because of electron-electron repulsions in addition to the crystal field effects on the repulsion of the metal electrons by the ligand electrons. -
Photochemical Generation of Carbenes and Ketenes from Phenanthrene-Based Precursors Part I: Dimethylalkylidene Part II: Diphenylketene
Colby College Digital Commons @ Colby Honors Theses Student Research 2017 Photochemical Generation of Carbenes and Ketenes from Phenanthrene-based Precursors Part I: Dimethylalkylidene Part II: Diphenylketene Tarini S. Hardikar Student Tarini Hardikar Colby College Follow this and additional works at: https://digitalcommons.colby.edu/honorstheses Part of the Organic Chemistry Commons Colby College theses are protected by copyright. They may be viewed or downloaded from this site for the purposes of research and scholarship. Reproduction or distribution for commercial purposes is prohibited without written permission of the author. Recommended Citation Hardikar, Tarini S. and Hardikar, Tarini, "Photochemical Generation of Carbenes and Ketenes from Phenanthrene-based Precursors Part I: Dimethylalkylidene Part II: Diphenylketene" (2017). Honors Theses. Paper 948. https://digitalcommons.colby.edu/honorstheses/948 This Honors Thesis (Open Access) is brought to you for free and open access by the Student Research at Digital Commons @ Colby. It has been accepted for inclusion in Honors Theses by an authorized administrator of Digital Commons @ Colby. Photochemical Generation of Carbenes and Ketenes from Phenanthrene-based Precursors Part I: Dimethylalkylidene Part II: Diphenylketene TARINI HARDIKAR A Thesis Presented to the Department of Chemistry, Colby College, Waterville, ME In Partial Fulfillment of the Requirements for Graduation With Honors in Chemistry SUBMITTED MAY 2017 Photochemical Generation of Carbenes and Ketenes from Phenanthrene-based Precursors Part I: Dimethylalkylidene Part II: Diphenylketene TARINI HARDIKAR Approved: (Mentor: Dasan M. Thamattoor, Professor of Chemistry) (Reader: Rebecca R. Conry, Associate Professor of Chemistry) “NOW WE KNOW” - Dasan M. Thamattoor Vitae Tarini Shekhar Hardikar was born in Vadodara, Gujarat, India in 1996. She graduated from the S.N. -
Optical and Collective Properties of Excitons in 2D Semiconductors
Optical and Collective Properties of Excitons in 2D Semiconductors by Matthew N. Brunetti A dissertation submitted to the Graduate Faculty in Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy, The City University of New York 2019 ii © 2019 Matthew N. Brunetti All Rights Reserved iii This manuscript has been read and accepted by the Graduate Faculty in Physics in satisfaction of the dissertation requirement for the degree of Doctor of Philosophy. Professor Oleg L. Berman Date Chair of Examining Committee Professor Igor L. Kuskovsky Date Executive Officer Professor Roman Ya. Kezerashvili Distinguished Professor Godfrey Gumbs Professor Antonios Balassis Professor Paula Fekete Supervisory Committee The City University of New York iv Abstract Optical and Collective Properties of Excitons in 2D Semiconductors by Matthew N. Brunetti Advisers: Professor Oleg L. Berman & Professor Roman Ya. Kezerashvili We study the properties of excitons in 2D semiconductors (2DSC) by numerically solv- ing the Schrödinger equation for an interacting electron and hole in the effective mass ap- proximation, then calculating optical properties such as the transition energies, oscillator strengths, and absorption coefficients. Our theoretical approach allows us to consider both direct excitons in monolayer (ML) 2DSC and spatially indirect excitons in heterostructures (HS) consisting of two 2DSC MLs separated by few-layer insulating hexagonal boron nitride (h-BN). In particular, we study indirect excitons in TMDC HS, namely MoS2, MoSe2, WS2, and WSe2; both direct and indirect excitons in the buckled 2D allotropes of silicon, germa- nium, and tin, known as silicene, germanene, and stanene respectively, or collectively as the Xenes; and both direct and indirect excitons in the anisotropic 2DSC phosphorene, the 2D allotrope of black phosphorus. -
Phosphorus: from the Stars to Land &
Phosphorus: From the Stars to Land & Sea The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Citation Cummins, Christopher C. “Phosphorus: From the Stars to Land & Sea.” Daedalus 143, no. 4 (October 2014): 9–20. As Published http://dx.doi.org/10.1162/DAED_a_00301 Publisher MIT Press Version Final published version Citable link http://hdl.handle.net/1721.1/92509 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. Phosphorus: From the Stars to Land & Sea Christopher C. Cummins Abstract: The chemistry of the element phosphorus offers a window into the diverse ½eld of inorganic chemistry. Fundamental investigations into some simple molecules containing phosphorus reveal much about the rami½cations of this element’s position in the periodic table and that of its neighbors. Addition - ally, there are many phosphorus compounds of commercial importance, and the industry surrounding this element resides at a crucial nexus of natural resource stewardship, technology, and modern agriculture. Questions about our sources of phosphorus and the applications for which we deploy it raise the provocative issue of the human role in the ongoing depletion of phosphorus deposits, as well as the transfer of phos- phorus from the land into the seas. Inorganic chemistry can be de½ned as “the chem- istry of all the elements of the periodic table,”1 but as such, the ½eld is impossibly broad, encompassing everything from organic chemistry to materials sci- ence and enzymology. -
Silicite: the Layered Allotrope of Silicon
Silicite: the layered allotrope of silicon Seymur Cahangirov,1 V. Ongun Oz¸celik,¨ 2, 3 Angel Rubio,1, ∗ and Salim Ciraci4, y 1Nano-Bio Spectroscopy Group and ETSF Scientific Development Centre, Departamento de F´ısica de Materiales, Universidad del Pa´ısVasco, CSIC-UPV/EHU-MPC and DIPC, Avenida de Tolosa 72, E-20018 San Sebastian, Spain 2UNAM-National Nanotechnology Research Center, Bilkent University, 06800 Ankara, Turkey 3Institute of Materials Science and Nanotechnology, Bilkent University, Ankara 06800, Turkey 4Department of Physics, Bilkent University, Ankara 06800, Turkey (Dated: September 28, 2018) Based on first-principles calculation we predict two new thermodynamically stable layered-phases of silicon, named as silicites, which exhibit strong directionality in the electronic and structural properties. As compared to silicon crystal, they have wider indirect band gaps but also increased absorption in the visible range making them more interesting for photovoltaic applications. These stable phases consistp p of intriguing stacking of dumbbell patterned silicene layers having trigonal structure with 3 × 3 periodicity of silicene and have cohesive energies smaller but comparable to that of the cubic diamond silicon. Our findings also provide atomic scale mechanisms for the growth of multilayer silicene as well as silicites. PACS numbers: 68.65.Ac, 73.61.Ey, 81.05.Dz I. INTRODUCTION II. METHODS We have performed state-of-the-art density functional Early studies1,2 to answer the critical question of theory (DFT) calculations within generalized gradi- ent approximation(GGA). We used projector-augmented whether Si can form graphene-like monolayer structures 14 have been ruled out initially by the arguments that Si wave potentials PAW and the exchange-correlation po- 3{5 tential is approximated with Perdew-Burke-Ernzerhof, does not have a layered allotrope like graphite . -
Iaps Newsletter 2006
IAPS NEWSLETTER 2006 2006 I-APS Newsletter, Volume 28, 2006 1 Contents Letter from the President 3 Letter from the I-APS Newsletter Editor 4 I-APS Officers ` 5 2007 I-APS Awards 6 2006 Porter Awards 6 Howard Zimmerman, the 2006 Porter Medal Laureate 7 Hiroshi Masuhara, the 2006 Porter Medal Laureate 9 2006 I-APS Award Winners 11 Photographs from the I-APS Award Session 15 Research Highlights from the 2006 I-APS Award Winner: Dan Nocera, “Microlasers for High Gain Chemo-/ Bio- Sensing on Small Length Scales” 16 Reports from 2006 Photochemical Meetings 28 In Memoriam Don Arnold 40 George Hammond 41 Upcoming conferences 44 I-APS Membership Form 45 I-APS Newsletter, Volume 28, 2006 2 Letter from the President Cornelia Bohne I-APS President (2006-08) Department of Chemistry University of Victoria PO Box 3065, Victoria, BC Canada V8W 3V6 1-250-7217151 [email protected] http://www.foto.chem.uvic.ca/ August, 2006 Dear Colleagues, I became president of the society a few days after the 17th I-APS Winter Conference held in Salvador, Brazil in June. The meeting was a great success with more than 150 participants, which included about 60 students. The informal atmosphere, leading to vibrant scientific discussions, showed how well integrated the South and North American photochemical communities are. The participation of so many young photochemists bodes well for the future of the photosciences and of the society. During the meeting the society awards were presented to Dan Nocera (I-APS award), Mohammad A. Omary (Young Investigator Award), Ryan C. -
Intercalation of Si Between Mos2 Layers Rik Van Bremen‡1, Qirong Yao‡1, Soumya Banerjee2, Deniz Cakir2, Nuri Oncel2 and Harold J
Intercalation of Si between MoS2 layers Rik van Bremen‡1, Qirong Yao‡1, Soumya Banerjee2, Deniz Cakir2, Nuri Oncel2 and Harold J. W. Zandvliet*1 Full Research Paper Open Access Address: Beilstein J. Nanotechnol. 2017, 8, 1952–1960. 1Physics of Interfaces and Nanomaterials, MESA+ Institute for doi:10.3762/bjnano.8.196 Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, Netherlands and 2Department of Physics and Received: 29 March 2017 Astrophysics, University of North Dakota, Grand Forks, ND 58202, Accepted: 21 August 2017 USA Published: 19 September 2017 Email: This article is part of the Thematic Series "Silicene, germanene and other Harold J. W. Zandvliet* - [email protected] group IV 2D materials". * Corresponding author ‡ Equal contributors Guest Editor: P. Vogt Keywords: © 2017 van Bremen et al.; licensee Beilstein-Institut. intercalation; molybdenum disulfide; scanning tunneling microscopy; License and terms: see end of document. silicene; two-dimensional materials Abstract We report a combined experimental and theoretical study of the growth of sub-monolayer amounts of silicon (Si) on molybdenum disulfide (MoS2). At room temperature and low deposition rates we have found compelling evidence that the deposited Si atoms intercalate between the MoS2 layers. Our evidence relies on several experimental observations: (1) Upon the deposition of Si on pristine MoS2 the morphology of the surface transforms from a smooth surface to a hill-and-valley surface. The lattice constant of the hill-and-valley structure amounts to 3.16 Å, which is exactly the lattice constant of pristine MoS2. (2) The transitions from hills to valleys are not abrupt, as one would expect for epitaxial islands growing on-top of a substrate, but very gradual.