DOCSLIB.ORG

Scope of Computational Organometallic Chemistry

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Scope of Computational Organometallic Chemistry Scope of Computational Organometallic Chemistry Structure, Reactivity and Properties Manuel Ángel Ortuño Maqueda PhD Thesis Theoretical and Computational Chemistry Supervisors: Gregori Ujaque Pérez Agustí Lledós Falcó Departament de Química Facultat de Ciències 2014 Universitat Autònoma de Barcelona Departament de Química Unitat de Química Física Memoria presentada para aspirar al Grado de Doctor por Manuel Ángel Ortuño Maqueda Manuel Ángel Ortuño Maqueda Visto bueno Gregori Ujaque Pérez Agustí Lledós Falcó Bellaterra, 9 de Septiembre de 2014 Acknowledgments I am delighted to dedicate this section to all people who have been involved, either actively or passively, in the dissertation. Unofficial Acknowledgments is mostly written in Spanish, my native language, whilst Official Acknowledgments is composed in English. Unofficial Acknowledgments “Al César lo que es del César”. Todo este trabajo ha sido posible gracias a mis directores de tesis, Gregori Ujaque y Agustí Lledós. Les estoy enormemente agradecido por la ciencia y los valores que me han enseñado, así como por la confianza que han depositado en mí todos estos años. I would also like to express my gratitude to Prof. Michael Bühl (University of St. Andrews) for his pleasant treatment and great support. Pero no habría sido capaz de llegar hasta aquí sin la excelente disciplina que aprendí de mis profesores en la Universidad de Almería, Ignacio Fernández de las Nieves y Fernando López Ortiz. Me acogieron en su laboratorio cuando aún estaba en la carrera y me transmitieron su gran motivación por la investigación. A toda la unidad de química física de la UAB por su cálida acogida. Mención especial para Carles Acosta, el sysadmin que más me ha aguantado, Xavi Solans, con quien he compartido —y sufrido— horas y horas de docencia biotecnóloga, ¡y la máquina Nespresso! To my colleagues abroad, particularly to Ludovic, Ava, Neetika and Lazaros, who made easier my stay in Scotland. I enjoyed the way we changed British tea time into Magic time. Al grupo transmet y a toda la gente que ha pasado por él: Aleix, Gabor y Óscar, entre otros muchos. A Salva por guiar mis primeros pasos sobre terreno computacional. A Pietro que, por lo mucho que me ha enseñado, podría haber sido mi tercer director de tesis. A Max, quien ha sido mi ejemplo a seguir durante todos estos años. A Laia Sparrow y Almudena por su agradable compañía. A Luca por sacarme siempre una carcajada con sus extrañas anéctodas. Y finalmente a Sergi, que pese a sus bacallades, ha sido un compañero genial y un amigo excepcional. A la célula biomet, con Jean-Didier a la cabeza. A Lur por sus deliciosos brownies y a Jaime por el humor absurdo con el que tanto nos reímos. A Bea por su eterna y contagiosa risa. A Victor por todas las pissarres y situaciones divertidas que sólo él es capaz de crear. A Elisabeth por la complicidad que nos caracteriza y los incontables Dunkins, cafés y frikadas varias que hemos disfrutado juntos. Last but not least, a Rosa por su gran ayuda y sinceridad; su amistad es una de las mejoras cosas que me llevo de esta etapa de mi vida. Volviendo al sur, a todos mis amigos de Almería, en particular a Alba, Alberto, Cristóbal, Jesús, Miguel, Nacho y Samanta. A pesar de todas las técnicas computacionales que he aprendido durante el doctorado, su apoyo moral sigue siendo incalculable. Por último, a mi padre Manuel, a mi madre Llani y a mi hermana Marta. Sé que la familia no se elige, pero si existiera tal posibilidad, no habría mejor elección que vosotros. Tenéis mi eterno agradecimiento por estar ahí siempre. Official Acknowledgments I would like to thank the Ministerio de Educación, Cultura y Deporte (Government of Spain) for (i) the predoctoral FPU fellowship that made possible the present PhD thesis and (ii) the travel scholarship that allowed me to stay for three months in the research group of Prof. Michael Bühl (University of St. Andrews). CESCA and BSC are also acknowledged for providing computational resources. Prof. Salvador Conejero (CSIC–Universidad de Sevilla, Instituto de Investigaciones Científicas) and Prof. Ernesto de Jesús (Universidad de Alcalá) are acknowledged for their collaboration in some of the studies presented herein. Make it simple, but significant. Don Draper in Mad Men List of Abbreviations The most common abbreviations used along the dissertation are collected as follows. Abbreviation Meaning AIMD Ab initio molecular dynamics B3LYP Becke’s three parameters, Lee–Yang–Parr density functional BZ Benzene CN Coordination number COD 1,5-Cyclooctadiene D3 Grimme’s dispersion function DCM Dichloromethane DFT Density functional theory Dipp 2,6-Diisopropylphenyl DMF Dimethylformamide DZ Double-ζ (zeta) en Ethylenediamine GIAO Gauge-including atomic orbitals HE Heck mechanism HI Hiyama mechanism HR Heck-reinsertion mechanism HT Heck-transmetalation mechanism IMe 1,3-Dimethylimidazol-2-ylidene IMes 1,3-Bis(2,4,6-trimethylphenyl)imidazol-2-ylidene IMes* 1,3-Bis(2,4,6-trimethylphenyl)-4,5-dimethylimidazol-2-ylidene IPr 1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene ItBu 1,3-Di-tert-butylimidazol-2-ylidene JTE Jahn–Teller effect M06 Zhao and Truhlar’s Minnesota 06 density functional MAD Mean absolute deviation MD Molecular dynamics MM Molecular mechanics NHC N-Heterocyclic carbene NHC' Cyclometalated N-heterocyclic carbene NMR Nuclear magnetic resonance OA Oxidative addition P–P Bis(phosphine) PBE0 Perdew–Burke–Ernzerhof hybrid density functional QM Quantum mechanics RDF Radial distribution function RE Reductive elimination σ-CAM σ-Complex assisted metathesis SMD Solvent model density SOMO Single occupied molecular orbital THF Tetrahydrofuran TOL Toluene TS Transition state TZ Triple-ζ (zeta) XC Exchange–correlation Atom Caption H Br C N I O F Rh Si Pd P Cl Pt Preface Long time ago, a younger version of myself decided to join the computational chemistry community in blind way. No regrets nowadays, it was totally worthy. Nobody could expect the outstanding and extensive knowledge I have received during these years of research training. I have learnt the potential of computation in resolving chemical problems as well as in understanding the essential engine of phenomena. After all, the final outcome has been captured in the text you already have in your hands. The dissertation I proudly present here pursues to reflect both the competence and the impact of computational chemistry in the organometallic chemistry scene. Forthcoming chapters are lightly overviewed as follows. Introduction gathers the general concepts of the topics under further discussion and provides a simplistic sketch of the theoretical methodology employed. Objectives points towards the general targets this work pretends to achieve. The body of the results is divided into three different parts. Structure analyses the geometry of paramagnetic Pt(III) complexes and evaluate the presence of agostic interactions in low-coordinate Pt(II) species. Reactivity unravels the reaction mechanisms of selected transition metal-mediated processes, i.e., C–H bond activation and cross-coupling reactions. Properties applies several computational methods to reproduce and predict some properties of transition metal compounds, in particular, NMR chemical shifts and acid dissociation constants. Conclusions collects the most important remarks obtained along the study. Ultimately, in Annex A and Annex B one can find the first page of the published material I am co-author of. I hope you enjoy the dissertation as much as I did. Thanks for reading and have fun! Manu Contents CHAPTER I: INTRODUCTION ............................................................................. 1 1. Organometallic Chemistry .................................................................................... 3 1.1. Structure of Transition Metal Complexes ................................................................. 6 1.1.1. Four-coordinate Pt(III) species .......................................................................................... 7 1.1.2. Three-coordinate Pt(II) species ......................................................................................... 9 1.2. Reaction Mechanisms .............................................................................................. 11 1.2.1. Pt(II) C–H bond activation .............................................................................................. 13 1.2.2. Cross-coupling reactions .................................................................................................. 14 1.2.3. Heck reaction ................................................................................................................... 16 1.3. Acidity of Dihydrogen Complexes .......................................................................... 17 1.4. Nuclear Magnetic Resonance of Transition Metals ................................................ 18 2. Computational Methods ...................................................................................... 21 2.1. Density Functional Theory ...................................................................................... 22 2.1.1. Classification of density functionals ................................................................................ 24 2.1.2. Which functional should one choose? ............................................................................ 27 2.2. Molecular Mechanics ............................................................................................... 29 2.3. Molecular Dynamics ...............................................................................................
Load more

Recommended publications
  • 1 Introduction to Early Main Group Organometallic Chemistry and Catalysis
    1 1 Introduction to Early Main Group Organometallic Chemistry and Catalysis Sjoerd Harder University Erlangen-Nürnberg, Inorganic and Organometallic Chemistry, Egerlandstrasse 1, 91058 Erlangen, Germany 1.1 Introduction Although organometallic complexes of the early main groups are well known for their very high reactivity and challenging isolation, they are among the first stud- ied during the pioneering beginnings of the field. Their high nucleophilicity and Brønsted basicity have made them to what they are today: strong polar reagents that are indispensible in modern organic synthesis. It is exactly this high reactivity that has made them potent catalysts for organic transformations that are gener- ally catalyzed by transition metal complexes. Despite their lack of partially filled d-orbitals and their inability to switch reversibly between oxidation states, the scope of their application in catalysis is astounding. As the early main group metal catalysis only started to become popular since the beginning of this century, it is still a young field with ample opportunities for further development. This intro- ductory chapter is specifically written for new graduate students in the field. It gives a very compact overview of the history of early main group organometallic chemistry, synthetic methods, bonding and structures, analytical methods, solu- tion dynamics, and some preliminary low-valent chemistry. This forms the basis for understanding their use in catalysis for which the basic steps are described in the second part of this chapter. For further in-depth information, the reader is referred to the individual chapters in this book. 1.2 s-Block Organometallics 1.2.1 Short History The organometallic chemistry of the highly electropositive early main group metals could not have started without the isolation of these elements in the metallic state.
    [Show full text]
  • Planar Cyclopenten‐4‐Yl Cations: Highly Delocalized Π Aromatics
    Angewandte Research Articles Chemie How to cite: Angew.Chem. Int. Ed. 2020, 59,18809–18815 Carbocations International Edition: doi.org/10.1002/anie.202009644 German Edition: doi.org/10.1002/ange.202009644 Planar Cyclopenten-4-yl Cations:Highly Delocalized p Aromatics Stabilized by Hyperconjugation Samuel Nees,Thomas Kupfer,Alexander Hofmann, and Holger Braunschweig* 1 B Abstract: Theoretical studies predicted the planar cyclopenten- being energetically favored by 18.8 kcalmolÀ over 1 (MP3/ 4-yl cation to be aclassical carbocation, and the highest-energy 6-31G**).[11–13] Thebishomoaromatic structure 1B itself is + 1 isomer of C5H7 .Hence,its existence has not been verified about 6–14 kcalmolÀ lower in energy (depending on the level experimentally so far.Wewere now able to isolate two stable of theory) than the classical planar structure 1C,making the derivatives of the cyclopenten-4-yl cation by reaction of bulky cyclopenten-4-yl cation (1C)the least favorable isomer.Early R alanes Cp AlBr2 with AlBr3.Elucidation of their (electronic) solvolysis studies are consistent with these findings,with structures by X-raydiffraction and quantum chemistry studies allylic 1A being the only observable isomer, notwithstanding revealed planar geometries and strong hyperconjugation the nature of the studied cyclopenteneprecursor.[14–18] Thus, interactions primarily from the C Al s bonds to the empty p attempts to generate isomer 1C,orits homoaromatic analog À orbital of the cationic sp2 carbon center.Aclose inspection of 1B,bysolvolysis of 4-Br/OTs-cyclopentene
    [Show full text]
  • An Analysis of Electrophilic Aromatic Substitution: a “Complex Approach” PCCP
    Volume 23 Number 9 7 March 2021 Pages 5033–5682 PCCP Physical Chemistry Chemical Physics rsc.li/pccp ISSN 1463-9076 PERSPECTIVE Janez Cerkovnik et al . An analysis of electrophilic aromatic substitution: a “complex approach” PCCP View Article Online PERSPECTIVE View Journal | View Issue An analysis of electrophilic aromatic substitution: a ‘‘complex approach’’† Cite this: Phys. Chem. Chem. Phys., a a b 2021, 23, 5051 Nikola Stamenkovic´, Natasˇa Poklar Ulrih and Janez Cerkovnik * Electrophilic aromatic substitution (EAS) is one of the most widely researched transforms in synthetic organic chemistry. Numerous studies have been carried out to provide an understanding of the nature of its reactivity pattern. There is now a need for a concise and general, but detailed and up-to-date, overview. The basic principles behind EAS are essential to our understanding of what the mechanisms underlying EAS are. To date, textbook overviews of EAS have provided little information about the Received 5th October 2020, mechanistic pathways and chemical species involved. In this review, the aim is to gather and present the Accepted 21st December 2020 up-to-date information relating to reactivity in EAS, with the implication that some of the key concepts DOI: 10.1039/d0cp05245k will be discussed in a scientifically concise manner. In addition, the information presented herein suggests certain new possibilities to advance EAS theory, with particular emphasis on the role of modern Creative Commons Attribution-NonCommercial 3.0 Unported Licence. rsc.li/pccp
    [Show full text]
  • 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.
    [Show full text]
  • 1 Introduction
    1 Field-control, phase-transitions, and life’s emergence 2 3 4 Gargi Mitra-Delmotte 1* and A.N. Mitra 2* 5 6 7 139 Cite de l’Ocean, Montgaillard, St.Denis 97400, REUNION. 8 e.mail : [email protected] 9 10 2Emeritius Professor, Department of Physics, Delhi University, INDIA; 244 Tagore Park, 11 Delhi 110009, INDIA; 12 e.mail : [email protected] 13 14 15 16 17 18 19 *Correspondence: 20 Gargi Mitra-Delmotte 1 21 e.mail : [email protected] 22 23 A.N. Mitra 2 24 e.mail : [email protected] 25 26 27 28 29 30 31 32 33 34 35 Number of words: ~11748 (without Abstract, references, tables, and figure legends) 36 7 figures (plus two figures in supplementary information files). 37 38 39 40 41 42 43 44 45 46 47 Abstract 48 49 Critical-like characteristics in open living systems at each organizational level (from bio- 50 molecules to ecosystems) indicate that non-equilibrium phase-transitions into absorbing 51 states lead to self-organized states comprising autonomous components. Also Langton’s 52 hypothesis of the spontaneous emergence of computation in the vicinity of a critical 53 phase-transition, points to the importance of conservative redistribution rules, threshold, 54 meta-stability, and so on. But extrapolating these features to the origins of life, brings up 55 a paradox: how could simple organics-- lacking the ‘soft matter’ response properties of 56 today’s complex bio-molecules--have dissipated energy from primordial reactions 57 (eventually reducing CO 2) in a controlled manner for their ‘ordering’? Nevertheless, a 58 causal link of life’s macroscopic irreversible dynamics to the microscopic reversible laws 59 of statistical mechanics is indicated via the ‘functional-takeover’ of a soft magnetic 60 scaffold by organics (c.f.
    [Show full text]
  • Preparation and Characterization of Iridium Hydride and Dihydrogen Complexes Relevant to Biomass Deoxygenation
    Preparation and Characterization of Iridium Hydride and Dihydrogen Complexes Relevant to Biomass Deoxygenation Jonathan M. Goldberg A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Washington 2017 Reading Committee: D. Michael Heinekey, Chair Karen I. Goldberg, Chair Brandi M. Cossairt Program Authorized to Offer Degree: Department of Chemistry © Copyright 2017 Jonathan M. Goldberg University of Washington Abstract Preparation and Characterization of Iridium Hydride and Dihydrogen Complexes Relevant to Biomass Deoxygenation Jonathan M. Goldberg Chairs of the Supervisory Committee: Professor D. Michael Heinekey Professor Karen I. Goldberg Department of Chemistry This thesis describes the fundamental organometallic reactivity of iridium pincer complexes and their applications to glycerol deoxygenation catalysis. These investigations provide support for each step of a previously proposed glycerol deoxygenation mechanism. Chapter 1 outlines the motivations for this work, specifically the goal of using biomass as a chemical feedstock over more common petroleum-based sources. A discussion of the importance of transforming glycerol to higher value products, such as 1,3-propanediol, is discussed. Chapter 2 describes investigations into the importance of pincer ligand steric factors on the coordination chemistry of the iridium metal center. Full characterization of a five-coordinate iridium-hydride complex is presented; this species was previously proposed to be a catalyst resting state for glycerol deoxygenation. Chapter 3 investigates hydrogen addition to R4(POCOP)Ir(CO) R4 3 t i R4 R4 3 [ POCOP = κ -C6H3-2,6-(OPR2)2 for R = Bu, Pr] and (PCP)Ir(CO) [ (PCP) = κ -C6H3-2,6- t i (CH2PR2)2 for R = Bu, Pr] to give cis- and/or trans-dihydride complexes.
    [Show full text]
  • Page 1 of 13 Pleasersc Do Not Advances Adjust Margins
    RSC Advances This is an Accepted Manuscript, which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. This Accepted Manuscript will be replaced by the edited, formatted and paginated article as soon as this is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. www.rsc.org/advances Page 1 of 13 PleaseRSC do not Advances adjust margins RSC Advances REVIEW Applications of supramolecular capsules derived from resorcin[4]arenes, calix[n]arenes and metallo-ligands: from Received 00th January 20xx, Accepted 00th January 20xx biology to catalysis a a,b a DOI: 10.1039/x0xx00000x Chiara M. A. Gangemi, Andrea Pappalardo* and Giuseppe Trusso Sfrazzetto* www.rsc.org/ Supramolecular architectures developed after the initial studies of Cram, Lehn and Pedersen have become structurally complexes but fascinating. In this context, supramolecular capsules based on resorcin[4]arenes, calix[n]arenes or metal- ligand structures are dynamic assemblies inspired to biological systems.
    [Show full text]
  • 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.
    [Show full text]
  • FAROOK COLLEGE (Autonomous)
    FAROOK COLLEGE (Autonomous) M.Sc. DEGREE PROGRAMME IN CHEMISTRY CHOICE BASED CREDIT AND SEMESTER SYSTEM-PG (FCCBCSSPG-2019) SCHEME AND SYLLABI 2019 ADMISSION ONWARDS 1 CERTIFICATE I hereby certify that the documents attached are the bona fide copies of the syllabus of M.Sc. Chemistry Programme to be effective from the academic year 2019-20 onwards. Date: Place: P R I N C I P A L 2 FAROOK COLLEGE (AUTONOMOUS) MSc. CHEMISTRY (CSS PATTERN) Regulations and Syllabus with effect from 2019 admission Pattern of the Programme a. The name of the programme shall be M.Sc. Chemistry under CSS pattern. b. The programme shall be offered in four semesters within a period of two academic years. c. Eligibility for admission will be as per the rules laid down by the College from time to time. d. Details of the courses offered for the programme are given in Table 1. The programme shall be conducted in accordance with the programme pattern, scheme of examination and syllabus prescribed. Of the 25 hours per week, 13 hours shall be allotted for theory and 12 hours for practical; 1 theory hour per week during even semesters shall be allotted for seminar. Theory Courses In the first three semesters, there will be four theory courses; and in the fourth semester, three theory courses. All the theory courses in the first and second semesters are core courses. In the third semester there will be three core theory courses and one elective theory course. College can choose any one of the elective courses given in Table 1.
    [Show full text]
  • Graphene Supported Rhodium Nanoparticles for Enhanced Electrocatalytic Hydrogen Evolution Reaction Ameerunisha Begum1*, Moumita Bose2 & Golam Moula2
    www.nature.com/scientificreports OPEN Graphene Supported Rhodium Nanoparticles for Enhanced Electrocatalytic Hydrogen Evolution Reaction Ameerunisha Begum1*, Moumita Bose2 & Golam Moula2 Current research on catalysts for proton exchange membrane fuel cells (PEMFC) is based on obtaining higher catalytic activity than platinum particle catalysts on porous carbon. In search of a more sustainable catalyst other than platinum for the catalytic conversion of water to hydrogen gas, a series of nanoparticles of transition metals viz., Rh, Co, Fe, Pt and their composites with functionalized graphene such as RhNPs@f-graphene, CoNPs@f-graphene, PtNPs@f-graphene were synthesized and characterized by SEM and TEM techniques. The SEM analysis indicates that the texture of RhNPs@f- graphene resemble the dispersion of water droplets on lotus leaf. TEM analysis indicates that RhNPs of <10 nm diameter are dispersed on the surface of f-graphene. The air-stable NPs and nanocomposites were used as electrocatalyts for conversion of acidic water to hydrogen gas. The composite RhNPs@f- graphene catalyses hydrogen gas evolution from water containing p-toluene sulphonic acid (p-TsOH) at an onset reduction potential, Ep, −0.117 V which is less than that of PtNPs@f-graphene (Ep, −0.380 V) under identical experimental conditions whereas the onset potential of CoNPs@f-graphene was at Ep, −0.97 V and the FeNPs@f-graphene displayed onset potential at Ep, −1.58 V. The pure rhodium nanoparticles, RhNPs also electrocatalyse at Ep, −0.186 V compared with that of PtNPs at Ep, −0.36 V and that of CoNPs at Ep, −0.98 V.
    [Show full text]
  • Transmetalation
    Organic Chemistry IV Organometallic Chemistry for Organic Synthesis Prof. Paul Knochel LMU 2015 1 OCIV Prüfung: Freitag 17. Juli 2015 9-11 Uhr Wieland HS Wiederholungsklausur: Donnerstag 17. September 2015 12-14 Uhr Baeyer HS 2 Recommended Literature 1. F. A. Carey, R. J. Sundberg, Advanced Organic Chemistry, Fifth Edition Part A and Part B, Springer, 2008, ISBN-13: 978-0-387-68346-1 2. R. Brückner, Organic Mechanisms, Springer, 2010, ISBN: 978-3-642- 03650-7 3. L. Kürti, B. Czako, Strategic applications of named reactions in organic synthesis, Elsevier, 2005, ISBN-13: 978-0-12-429785-2 4. N. Krause, Metallorganische Chemie, Spektrum der Wissenschaft, 1996, ISBN: 3-86025-146-5 5. R. H. Crabtree, The organometallic chemistry of transition metals, Wiley- Interscience, 2005, ISBN: 0-471-66256-9 6. M. Schlosser, Organometallics in Synthesis – A manual, 2nd edition, Wiley, 2002, ISBN: 0-471-98416-7 7. K. C. Nicolaou, T. Montagnon, Molecules that changed the world, Wiley- VCH, 2008, ISBN: 978-527-30983-2 8. J. Hartwig, Organotransition Metal Chemistry: From Bonding to Catalysis, Palgrave Macmillan, 2009, ISBN-13: 978-1891389535 9. P. Knochel, Handbook of Functionalized Organometallics, Volume 1 und 2, Wiley-VCH, 2005, ISBN-13: 978-3-527-31131-6 3 Importance of organometallics 4 Industrial production Industrial annual production of various organometallics Organometallic production [T / year] Si 700 000 Pb 600 000 Al 50 000 Sn 35 000 Li 900 5 Organometallic reagents and catalysts for the organic synthesis 6 Historic point of view 1757 - Louis Cadet de Gassicourt (parisian apothecary) E. Frankland (1848), University of Marburg, initial goal: synthesis of an ethyl radical Universität Marburg (1848) 7 Organometallic chemistry of the XIX century 8 Organometallic chemistry of the XIX century 9 Reactivity of the Grignard reagents 10 Historic point of view Victor Grignard (1900) Karl Ziegler (1919) 11 Historic point of view first transition metal organometallics: Hein (1919) 12 Historic point of view 1951 : synthesis of ferrocene Pauson (Scotland) 7.
    [Show full text]
  • Anagostic Interactions Under Pressure: Attractive Or Repulsive? Wolfgang Scherer *[A], Andrew C
    Manuscript Click here to download Manuscript: manuscript_final.pdf ((Attractive or repulsive?)) DOI: 10.1002/anie.200((will be filled in by the editorial staff)) Anagostic Interactions under Pressure: Attractive or Repulsive? Wolfgang Scherer *[a], Andrew C. Dunbar [a], José E. Barquera-Lozada [a], Dominik Schmitz [a], Georg Eickerling [a], Daniel Kratzert [b], Dietmar Stalke [b], Arianna Lanza [c,d], Piero Macchi*[c], Nicola P. M. Casati [d], Jihaan Ebad-Allah [a] and Christine Kuntscher [a] The term “anagostic interactions” was coined in 1990 by Lippard preagostic interactions are considered to lack any “involvement of 2 and coworkers to distinguish sterically enforced M•••H-C contacts dz orbitals in M•••H-C interactions” and rely mainly on M(dxz, yz) (M = Pd, Pt) in square-planar transition metal d8 complexes from o V (C-H) S-back donation.[3b] attractive, agostic interactions.[1a] This classification raised the fundamental question whether axial M•••H-C interaction in planar The first observation of unusual axial M•••H-C interaction in 8 8 d -ML4 complexes represent (i) repulsive anagostic 3c-4e M•••H-C planar d -ML4 complexes was made by S. Trofimenko, who interactions[1] (Scheme 1a) or (ii) attractive 3c-4e M•••H-C pioneered the chemistry of transition metal pyrazolylborato hydrogen bonds[2] (Scheme 1b) in which the transition metal plays complexes.[5,6] Trofimenko also realized in 1968, on the basis of the role of a hydrogen-bond acceptor (Scheme 1b). The latter NMR studies, that the shift of the pseudo axial methylene protons in 3 bonding description is related to another bonding concept which the agostic species [Mo{Et2B(pz)2}(K -allyl)(CO)2] (1) (pz = describes these M•••H-C contacts in terms of (iii) pregostic or pyrazolyl; allyl = H2CCHCH2) “is comparable in magnitude but [3] preagostic interactions (Scheme 1c) which are considered as being different in direction from that observed in Ni[Et2B(pz)2]2” (2) “on the way to becoming agostic, or agostic of the weak type”.[4] (Scheme 2).[6,7] Scheme 1.
    [Show full text]