N-Heterocyclic Carbenes (Nhcs)
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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". -
Perspectives on How Nature Employs the Principles of Organometallic Chemistry in Dihydrogen Activation in Hydrogenases†
4682 Organometallics 2010, 29, 4682–4701 DOI: 10.1021/om100436c Perspectives on How Nature Employs the Principles of Organometallic Chemistry in Dihydrogen Activation in Hydrogenases† John C. Gordon* and Gregory J. Kubas* Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States Received May 6, 2010 Relatively recent developments in metalloenzyme and organometallic chemistry have targeted a growing link between these outwardly incongruous fields, giving birth to a merger now popularly termed “bio-organometallic” chemistry. The astonishing discovery of CO and CN ligands bound to dinuclear iron sites in billion-year-old hydrogenase enzymes has led to a new paradigm and triggered an explosion of research on bioinspired chemistry. The article will focus on the impressive array of organometallic chemistry principles that work in concert in the structure and function of H2ases. Molecular H2 is at the forefront of bioinspired energy, and its production and storage are critical for renewable energy systems. Biomimetic inorganic chemistry and photochemistry involving water splitting for H2 production has erupted in the past decade and will also be reflected upon here. I. Introduction be despised and avoided by nature. This view was shattered by the relatively recent discovery, initially spectroscopically2,3 then At the macroscopic level, nature displays dazzling beauty crystallographically,4 of CO and CN ligands bound to dinuclear and surprises on a regular basis. On the molecular level, its iron sites in hydrogenase (H2ase) enzymes that have existed in mystique is even more fascinating to biologists and chemists numerous microorganisms for over a billion years. It is now in all their subfields. -
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. -
The Chemistry of Carbene-Stabilized
THE CHEMISTRY OF CARBENE-STABILIZED MAIN GROUP DIATOMIC ALLOTROPES by MARIHAM ABRAHAM (Under the Direction of Gregory H. Robinson) ABSTRACT The syntheses and molecular structures of carbene-stabilized arsenic derivatives of 1 1 i 1 1 AsCl3 (L :AsCl3 (1); L : = :C{N(2,6- Pr2C6H3)CH}2), and As2 (L :As–As:L (2)), are presented herein. The potassium graphite reduction of 1 afforded the carbene-stabilized diarsenic complex, 2. Notably, compound 2 is the first Lewis base stabilized diatomic molecule of the Group 13–15 elements, in the formal oxidation state of zero, in the fourth period or lower of the Periodic Table. Compound 2 contains one As–As σ-bond and two lone pairs of electrons on each arsenic atom. In an effort to study the chemistry of the electron-rich compound 2, it was combined with an electron-deficient Lewis acid, GaCl3. The addition of two equivalents of GaCl3 to 2 resulted in one-electron oxidation of 2 to 1 1 •+ – •+ – give [L :As As:L ] [GaCl4] (6 [GaCl4] ). Conversely, the addition of four equivalents of GaCl3 to 2 resulted in two- electron oxidation of 2 to give 1 1 2+ – 2+ – •+ [L :As=As:L ] [GaCl4 ]2 (6 [GaCl4 ]2). Strikingly, 6 represents the first arsenic radical to be structurally characterized in the solid state. The research project also explored the reactivity of carbene-stabilized disilicon, (L1:Si=Si:L1 (7)), with borane. The reaction of 7 with BH3·THF afforded two unique compounds: one containing a parent silylene (:SiH2) unit (8), and another containing a three-membered silylene ring (9). -
Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc
Metal-Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc Richard H. Duncan Lyngdoh*,a, Henry F. Schaefer III*,b and R. Bruce King*,b a Department of Chemistry, North-Eastern Hill University, Shillong 793022, India B Centre for Computational Quantum Chemistry, University of Georgia, Athens GA 30602 ABSTRACT: This survey of metal-metal (MM) bond distances in binuclear complexes of the first row 3d-block elements reviews experimental and computational research on a wide range of such systems. The metals surveyed are titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc, representing the only comprehensive presentation of such results to date. Factors impacting MM bond lengths that are discussed here include (a) n+ the formal MM bond order, (b) size of the metal ion present in the bimetallic core (M2) , (c) the metal oxidation state, (d) effects of ligand basicity, coordination mode and number, and (e) steric effects of bulky ligands. Correlations between experimental and computational findings are examined wherever possible, often yielding good agreement for MM bond lengths. The formal bond order provides a key basis for assessing experimental and computationally derived MM bond lengths. The effects of change in the metal upon MM bond length ranges in binuclear complexes suggest trends for single, double, triple, and quadruple MM bonds which are related to the available information on metal atomic radii. It emerges that while specific factors for a limited range of complexes are found to have their expected impact in many cases, the assessment of the net effect of these factors is challenging. -
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. -
Carbene Metal Amide Photoemitters: Tailoring Conformationally Flexible Amides for Full Color Range Emissions Including White-Emi
Chemical Science View Article Online EDGE ARTICLE View Journal | View Issue Carbene metal amide photoemitters: tailoring conformationally flexible amides for full color Cite this: Chem. Sci., 2020, 11,435 † All publication charges for this article range emissions including white-emitting OLED have been paid for by the Royal Society a b b of Chemistry Alexander S. Romanov, * Saul T. E. Jones, Qinying Gu, Patrick J. Conaghan, b Bluebell H. Drummond, b Jiale Feng, b Florian Chotard, a Leonardo Buizza, b Morgan Foley, b Mikko Linnolahti, *c Dan Credgington *b and Manfred Bochmann *a Conformationally flexible “Carbene–Metal–Amide” (CMA) complexes of copper and gold have been developed based on a combination of sterically hindered cyclic (alkyl)(amino)carbene (CAAC) and 6- and 7-ring heterocyclic amide ligands. These complexes show photoemissions across the visible spectrum with PL quantum yields of up to 89% in solution and 83% in host-guest films. Single crystal X-ray diffraction and photoluminescence (PL) studies combined with DFT calculations indicate the important Creative Commons Attribution 3.0 Unported Licence. role of ring structure and conformational flexibility of the amide ligands. Time-resolved PL shows efficient delayed emission with sub-microsecond to microsecond excited state lifetimes at room Received 12th September 2019 À temperature, with radiative rates exceeding 106 s 1. Yellow organic light-emitting diodes (OLEDs) based Accepted 12th November 2019 on a 7-ring gold amide were fabricated by thermal vapor deposition, while the sky-blue to warm-white DOI: 10.1039/c9sc04589a mechanochromic behavior of the gold phenothiazine-5,5-dioxide complex enabled fabrication of the rsc.li/chemical-science first CMA-based white light-emitting OLED. -
Cyclopentadienyl Compounds of the First Row Transition Metals And
University of Vermont ScholarWorks @ UVM Graduate College Dissertations and Theses Dissertations and Theses 2017 Cyclopentadienyl Compounds of the First Row Transition Metals and Early Actinides: Novel Main-Group Bond Forming Catalysis and New Metallacycles Justin Kane Pagano University of Vermont Follow this and additional works at: https://scholarworks.uvm.edu/graddis Part of the Chemistry Commons Recommended Citation Pagano, Justin Kane, "Cyclopentadienyl Compounds of the First Row Transition Metals and Early Actinides: Novel Main-Group Bond Forming Catalysis and New Metallacycles" (2017). Graduate College Dissertations and Theses. 700. https://scholarworks.uvm.edu/graddis/700 This Dissertation is brought to you for free and open access by the Dissertations and Theses at ScholarWorks @ UVM. It has been accepted for inclusion in Graduate College Dissertations and Theses by an authorized administrator of ScholarWorks @ UVM. For more information, please contact [email protected]. CYCLOPENTADIENYL COMPOUNDS OF THE FIRST ROW TRANSITION METALS AND EARLY ACTINIDES: NOVEL MAIN-GROUP BOND FORMING CATALYSIS AND NEW METALLACYCLES A Dissertation Presented by Justin Kane Pagano to The Faculty of the Graduate College of The University of Vermont In Partial Fulfilment of the Requirements For the Degree of Doctor of Philosophy Specializing in Chemistry May, 2017 Defense Date: November 29, 2016 Dissertation Examination Committee: Rory Waterman, Ph. D., Advisor John M. Hughes, Ph. D., Chairperson Matthias Brewer, Ph. D. Jaqueline L. Kiplinger, Ph. D. Matthew D. Liptak, Ph. D. Cynthia J. Forehand, Ph. D., Dean of the Graduate College ABSTRACT Cyclopentadienyl first row transition-metal compounds have been well studied 5 since the 1950’s, with the nearly ubiquitous CpFe(CO)2Me (FpMe) (Cp = η -C5H5) being one of the first organometallics to be fully characterized. -
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Chemical Science View Article Online EDGE ARTICLE View Journal | View Issue Nickel-catalyzed cyclization of alkyne-nitriles with organoboronic acids involving anti- Cite this: Chem. Sci.,2016,7,5815 carbometalation of alkynes† Xingjie Zhang, Xin Xie and Yuanhong Liu* A nickel-catalyzed regioselective addition/cyclization of o-(cyano)phenyl propargyl ethers with arylboronic acids has been developed, which provides an efficient protocol for the synthesis of highly functionalized Received 16th March 2016 1-naphthylamines with wide structural diversity. The reaction is characterized by a regioselective and Accepted 19th May 2016 anti-addition of the arylboronic acids to the alkyne and subsequent facile nucleophilic addition of the DOI: 10.1039/c6sc01191h resulting alkenylmetal to the tethered cyano group. Mechanistic studies reveal that a Ni(I) species might www.rsc.org/chemicalscience be involved in the catalytic process. to an exo-alkene upon cyclization3,4 (Scheme 1, eqn (1)). Creative Commons Attribution 3.0 Unported Licence. Introduction Cyclizations involving the regioselective formation of the Transition-metal-catalyzed cascade reactions consisting of alkenylmetal with a metal a-to the R1 substituent such as syn-B 5 multiple carbometalation steps have attracted considerable are quite rare (Scheme 1, eqn (2)), possibly because the attention in organic synthesis since these processes enable the subsequent cyclization process will involve a highly strained rapid assembly of complex structures in an efficient, atom- transition state. Thus, -
On the Road to Carbene and Carbyne Complexes
ON THE ROAD TO CARBENE AND CARBYNE COMPLEXES Nobel Lecture, 11 December 1973 by ERNST OTTO FISCHER Inorganic Chemistry Laboratory, Technical University, Munich, Federal Republic of Germany Translation from the German text INTRODUCTION In the year 1960, I had the honour of giving a talk at this university* about sandwich complexes on which we were working at that time. I think I do not have to repeat the results of those investigations today. I would like to talk instead about a field of research in which we have been intensely interested in recent years: namely, the field of carbene complexes and, more recently, carbyne complexes. If we substitute one of the hydrogen atoms in a hydrocarbon of the alkane type - for example, ethane - by a metal atom, which can of course bind many more ligands, we arrive at an organometallic compound in which the organic radical is bound to the metal atom by a σ-bond (Fig. la). The earliest compounds of this kind were prepared more than a hundred years ago; the first was cacodyl, prepared by R. Bunsen (1), and then zinc dialkyls were prepared by E. Frankland (2). Later V. Grignard was able to synthesise alkyl magnesium halides by treating magnesium with alkyl halides (3). Grignard was awarded the Nobel Prize in 1912 for this effort. We may further recall the organo-aluminium compounds (4) of K. Ziegler which form the basis for the low pressure polymerisation, for example of ethylene. Ziegler and G. Natta were together honoured with the Nobel Prize in 1963 for their work on organometallic compounds. -
Synthesis and Reactivity of Cyclopentadienyl Based Organometallic Compounds and Their Electrochemical and Biological Properties
Synthesis and reactivity of cyclopentadienyl based organometallic compounds and their electrochemical and biological properties Sasmita Mishra Department of Chemistry National Institute of Technology Rourkela Synthesis and reactivity of cyclopentadienyl based organometallic compounds and their electrochemical and biological properties Dissertation submitted to the National Institute of Technology Rourkela In partial fulfillment of the requirements of the degree of Doctor of Philosophy in Chemistry by Sasmita Mishra (Roll Number: 511CY604) Under the supervision of Prof. Saurav Chatterjee February, 2017 Department of Chemistry National Institute of Technology Rourkela Department of Chemistry National Institute of Technology Rourkela Certificate of Examination Roll Number: 511CY604 Name: Sasmita Mishra Title of Dissertation: ''Synthesis and reactivity of cyclopentadienyl based organometallic compounds and their electrochemical and biological properties We the below signed, after checking the dissertation mentioned above and the official record book(s) of the student, hereby state our approval of the dissertation submitted in partial fulfillment of the requirements of the degree of Doctor of Philosophy in Chemistry at National Institute of Technology Rourkela. We are satisfied with the volume, quality, correctness, and originality of the work. --------------------------- Prof. Saurav Chatterjee Principal Supervisor --------------------------- --------------------------- Prof. A. Sahoo. Prof. G. Hota Member (DSC) Member (DSC) --------------------------- -
Expedient Syntheses of the N-Heterocyclic Carbene Precursor Imidazolium Salts Ipr·Hcl, Imes·Hcl and Ixy·Hcl
Expedient syntheses of the N-heterocyclic carbene precursor imidazolium salts IPr·HCl, IMes·HCl and IXy·HCl Lukas Hintermann Full Research Paper Open Access Address: Beilstein Journal of Organic Chemistry 2007, 3, No. 22. Institute of Organic Chemistry, RWTH Aachen University, Landoltweg doi:10.1186/1860-5397-3-22 1, D-52074 Aachen, Germany Received: 25 June 2007 Email: Accepted: 28 August 2007 Lukas Hintermann - [email protected] Published: 28 August 2007 © 2007 Hintermann; licensee Beilstein-Institut License and terms: see end of document. Abstract The 1,3-diaryl-imidazolium chlorides IPr·HCl (aryl = 2,6-diisopropylphenyl), IMes·HCl (aryl = 2,4,6-trimethylphenyl) and IXy·HCl (aryl = 2,6-dimethylphenyl), precursors to widely used N-heterocyclic carbene (NHC) ligands and catalysts, were prepared in high yields (81%, 69% and 89%, respectively) by the reaction of 1,4-diaryl-1, 4-diazabutadienes, paraformaldehyde and chloro- trimethylsilane in dilute ethyl acetate solution. A reaction mechanism involving a 1,5-dipolar electrocyclization is proposed. Background Imidazolylidene carbenes have been investigated as ligands in coordination chemistry, as powerful steering/controlling elements in transition-metal catalysis,[1,2] and more recently as metal-free catalysts for organic reactions[3,4]. Some prominent members of the family of N-heterocyclic carbenes (NHC) are the sterically encumbered imidazolylidenes IPr and IMes (Figure 1), which can also be considered as analogues of bulky and electron-rich tertiary phosphanes. In contrast to the latter, their synthesis does not involve air-sensitive or pyrophoric organometallic reagents, and they are conveniently stored and used in the form of their air-stable precursors, namely the imidazolium salts IPr·HCl (1,3-bis-{2,6- diisopropylphenyl}imidazolium chloride; 1) or IMes·HCl (1,3- bis-{2,4,6-trimethylphenyl}imidazolium chloride; 2) (Figure 1).