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Topological Analysis of the Metal-Metal Bond: a Tutorial Review Christine Lepetit, Pierre Fau, Katia Fajerwerg, Myrtil L
Topological analysis of the metal-metal bond: A tutorial review Christine Lepetit, Pierre Fau, Katia Fajerwerg, Myrtil L. Kahn, Bernard Silvi To cite this version: Christine Lepetit, Pierre Fau, Katia Fajerwerg, Myrtil L. Kahn, Bernard Silvi. Topological analysis of the metal-metal bond: A tutorial review. Coordination Chemistry Reviews, Elsevier, 2017, 345, pp.150-181. 10.1016/j.ccr.2017.04.009. hal-01540328 HAL Id: hal-01540328 https://hal.sorbonne-universite.fr/hal-01540328 Submitted on 16 Jun 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Topological analysis of the metal-metal bond: a tutorial review Christine Lepetita,b, Pierre Faua,b, Katia Fajerwerga,b, MyrtilL. Kahn a,b, Bernard Silvic,∗ aCNRS, LCC (Laboratoire de Chimie de Coordination), 205, route de Narbonne, BP 44099, F-31077 Toulouse Cedex 4, France. bUniversité de Toulouse, UPS, INPT, F-31077 Toulouse Cedex 4, i France cSorbonne Universités, UPMC, Univ Paris 06, UMR 7616, Laboratoire de Chimie Théorique, case courrier 137, 4 place Jussieu, F-75005 Paris, France Abstract This contribution explains how the topological methods of analysis of the electron density and related functions such as the electron localization function (ELF) and the electron localizability indicator (ELI-D) enable the theoretical characterization of various metal-metal (M-M) bonds (multiple M-M bonds, dative M-M bonds). -
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 -
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 -
Course No: CH15101CR Title: Inorganic Chemistry (03 Credits)
Course No: CH15101CR Title: Inorganic Chemistry (03 Credits) Max. Marks: 75 Duration: 48 Contact hours (48L) End Term Exam: 60 Marks Continuous Assessment: 15 Marks Unit-I Stereochemistry and Bonding in the Compounds of Main Group Elements (16 Contact hours) Valence bond theory: Energy changes taking place during the formation of diatomic molecules; factors affecting the combined wave function. Bent's rule and energetics of hybridization. Resonance: Conditions, resonance energy and examples of some inorganic molecules/ions. Odd Electron Bonds: Types, properties and molecular orbital treatment. VSEPR: Recapitulation of assumptions, shapes of trigonal bypyramidal, octahedral and - 2- 2- pentagonal bipyramidal molecules / ions. (PCl5, VO3 , SF6, [SiF6] , [PbCl6] and IF7). Limitations of VSEPR theory. Molecular orbital theory: Salient features, variation of electron density with internuclear distance. Relative order of energy levels and molecular orbital diagrams of some heterodiatomic molecules /ions. Molecular orbital diagram of polyatomic molecules / ions. Delocalized Molecular Orbitals: Butadiene, cyclopentadiene and benzene. Detection of Hydrogen Bond: UV-VIS, IR and X-ray. Importance of hydrogen bonding. Unit-II Metal-Ligand Equilibria in Solution (16 Contact hours) Stepwise and overall formation constants. Inert & labile complexes. Stability of uncommon oxidation states. Metal Chelates: Characteristics, Chelate effect and the factors affecting stability of metal chelates. Determination of formation constants by pH- metry and spectrophotometry. Structural (ionic radii) and thermodynamic (hydration and lattice energies) effects of crystal field splitting. Jahn -Teller distortion, spectrochemical series and the nephleuxetic effect. Evidence of covalent bonding in transition metal complexes. Unit-III Pi-acid Metal Complexes (16 Contact hours) Transition Metal Carbonyls: Carbon monoxide as ligand, synthesis, reactions, structures and bonding of mono- and poly-nuclear carbonyls. -
Aromaticity Sem- Ii
AROMATICITY SEM- II In 1931, German chemist and physicist Sir Erich Hückel proposed a theory to help determine if a planar ring molecule would have aromatic properties .This is a very popular and useful rule to identify aromaticity in monocyclic conjugated compound. According to which a planar monocyclic conjugated system having ( 4n +2) delocalised (where, n = 0, 1, 2, .....) electrons are known as aromatic compound . For example: Benzene, Naphthalene, Furan, Pyrrole etc. Criteria for Aromaticity 1) The molecule is cyclic (a ring of atoms) 2) The molecule is planar (all atoms in the molecule lie in the same plane) 3) The molecule is fully conjugated (p orbitals at every atom in the ring) 4) The molecule has 4n+2 π electrons (n=0 or any positive integer Why 4n+2π Electrons? According to Hückel's Molecular Orbital Theory, a compound is particularly stable if all of its bonding molecular orbitals are filled with paired electrons. - This is true of aromatic compounds, meaning they are quite stable. - With aromatic compounds, 2 electrons fill the lowest energy molecular orbital, and 4 electrons fill each subsequent energy level (the number of subsequent energy levels is denoted by n), leaving all bonding orbitals filled and no anti-bonding orbitals occupied. This gives a total of 4n+2π electrons. - As for example: Benzene has 6π electrons. Its first 2π electrons fill the lowest energy orbital, and it has 4π electrons remaining. These 4 fill in the orbitals of the succeeding energy level. The criteria for Antiaromaticity are as follows: 1) The molecule must be cyclic and completely conjugated 2) The molecule must be planar. -
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. -
Organometallic Compounds
Chapter 11 Organometallic compounds Organometallics Reactions using organometallics Organometallic compounds Ch 11 #2 = comp’s containing a carbon-metal bond δ− δ+ C in organometallic comp’ds are nucleophilic. C in organic comp’d (like ROH, RNH , and RX) 2 δ+ δ are electrophilic. − due to ∆EN Ch 11 #3 in substitution reactions a carbon Nu: R-Li and R-MgX Ch 11 #4 (used to be) the two most common organometallics organolithium comp’ds BuLi = an alkyl lithium organomagnesium comp’ds = Grignard reagents 1912 Nobel Prize R, Ar, vinyl all possible; Br (as X) popular Ether (solvent) coordinates Mg, stabilizing it. Reactions of R-Li and R-MgX Ch 11 #5 reacts like a carbanion C:– ~ a C Nu: reactions as C Nu: (like SN(2)) nucleophilic addition to carbonyls ~ more often Chapt 16 Ch 11 #6 R-Li and R-MgX are very strong B: how strong? pKa? − − react even with very weak acid stronger than OH? NH2? useful for preparing deuterated HC Storage and reaction must be acid- and moisture-free. Transmetal(l)ation Ch 11 #7 R-Li is more reactive than R-MgX is. C–Li more polar than C–Mg C of R-Li more nu-philic [better Nu:] transmetalation [metal exchange] to less reactive [more stable] organometallic Coupling using Gilman reagent Ch 11 #8 coupling reaction (in organic chemistry) two hydrocarbon fragments are coupled (to form C–C) with the aid of a (transition) metal catalyst Gilman reagent coupling of R of R-X and R’ of Gilman reagent RX + R’2CuLi R–R’ mechanism? substitution of X with R’? not clear Ch 11 #9 R can be alkyl, aryl, or alkenyl [vinyl] which is not possible by R-Li or R-MgX Is R of Gilman why? they are SN(2). -
Structures and Reaction Mechanisms of Organocuprate Clusters in Organic Chemistry
REVIEWS Wherefore Art Thou Copper? Structures and Reaction Mechanisms of Organocuprate Clusters in Organic Chemistry Eiichi Nakamura* and Seiji Mori Organocopper reagents provide the principles. This review will summarize example of molecular recognition and most general synthetic tools in organic first the general structural features of supramolecular chemistry, which chemistry for nucleophilic delivery of organocopper compounds and the pre- chemists have long exploited without hard carbanions to electrophilic car- vious mechanistic arguments, and then knowing it. Reasoning about the bon centers. A number of structural describe the most recent mechanistic uniqueness of the copper atom among and mechanistic studies have been pictures obtained through high-level neighboring metal elements in the reported and have led to a wide variety quantum mechanical calculations for periodic table will be presented. of mechanistic proposals, some of three typical organocuprate reactions, which might even be contradictory to carbocupration, conjugate addition, Keywords: catalysis ´ conjugate addi- others. With the recent advent of and SN2 alkylation. The unified view tions ´ copper ´ density functional physical and theoretical methodolo- on the nucleophilic reactivities of met- calculations ´ supramolecular chemis- gies, the accumulated knowledge on al organocuprate clusters thus ob- try organocopper chemistry is being put tained has indicated that organocup- together into a few major mechanistic rate chemistry represents an intricate 1. Introduction 1 R Cu X The desire to learn about the nature of elements has been R or R1 R and will remain a main concern of chemists. In this review, we R Cu will consider what properties of copper make organocopper R1 chemistry so useful in organic chemistry. -
Organometrallic Chemistry
CHE 425: ORGANOMETALLIC CHEMISTRY SOURCE: OPEN ACCESS FROM INTERNET; Striver and Atkins Inorganic Chemistry Lecturer: Prof. O. G. Adeyemi ORGANOMETALLIC CHEMISTRY Definitions: Organometallic compounds are compounds that possess one or more metal-carbon bond. The bond must be “ionic or covalent, localized or delocalized between one or more carbon atoms of an organic group or molecule and a transition, lanthanide, actinide, or main group metal atom.” Organometallic chemistry is often described as a bridge between organic and inorganic chemistry. Organometallic compounds are very important in the chemical industry, as a number of them are used as industrial catalysts and as a route to synthesizing drugs that would not have been possible using purely organic synthetic routes. Coordinative unsaturation is a term used to describe a complex that has one or more open coordination sites where another ligand can be accommodated. Coordinative unsaturation is a very important concept in organotrasition metal chemistry. Hapticity of a ligand is the number of atoms that are directly bonded to the metal centre. Hapticity is denoted with a Greek letter η (eta) and the number of bonds a ligand has with a metal centre is indicated as a superscript, thus η1, η2, η3, ηn for hapticity 1, 2, 3, and n respectively. Bridging ligands are normally preceded by μ, with a subscript to indicate the number of metal centres it bridges, e.g. μ2–CO for a CO that bridges two metal centres. Ambidentate ligands are polydentate ligands that can coordinate to the metal centre through one or more atoms. – – – For example CN can coordinate via C or N; SCN via S or N; NO2 via N or N. -
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. -
Unit 11 Halogen Derivatives
UNIT 11 HALOGEN DERIVATIVES Structure 11.1 Introduction Objectives 11.2 Classification of Halogen Derivatives 11.3 Preparation of Halogen Derivatives Alkyl Halides Aryl Halides Alkenyl Halides 11.4 Structure and Properties of Halogen Derivatives Structure of Halogen Derivatives Physical Properties of Halogen Derivatives Spectral Properties of Halogen Derivatives Chemical Properties of Alkyl Halides Chemical Properties of Aryl and Alkenyl Halides 11.5 Organometallic Compounds 11.6 Polyhalogen Derivatives Dihalogen Derivatives Trihalogen Derivatives 11.7 Uses of Halogen Derivatives 11.8 Lab Detection 11.9 Summary 11.10 Terminal Questions 11.11 Answers 11.1 INTRODUCTION In Block 2, we have described the preparation and reactions of hydrocarbons and some heterocyclic compounds. In this unit and in the next units, we will srudy some derivatives of hydrocarbons. Replacement of one or more hydrogen atoms in a hycimcarbon by halogen atom(s) [F, CI, Br, or I:] gives the halogen derivatives. These compounds are important laboratory and industrial solvents and serve as intermediates in the synthesis of other organic compounds. Many chlorohydrocarbons have acquired importance as insecticides. Although there are not many naturally occurring halogen derivatives yet you might be familiar with one such compound, thyroxin-a thyroid hormone. In this unit, we shall take up the chemistry of the halogen derivatives in detail beginning with classification of halogen derivatives and then going over to methods of their preparation. We shall also discuss the reactivity'of halogen compounds and focus our attention specially, on some important reactions such as nucleophilic substitution (SN)and elimination (E) reactions. Finally, we shall take up uses of halogen derivatives and the methods for their detection. -
Chapter 7 - Alkenes and Alkynes I
Andrew Rosen Chapter 7 - Alkenes and Alkynes I 7.1 - Introduction - The simplest member of the alkenes has the common name of ethylene while the simplest member of the alkyne family has the common name of acetylene 7.2 - The (E)-(Z) System for Designating Alkene Diastereomers - To determine E or Z, look at the two groups attached to one carbon atom of the double bond and decide which has higher priority. Then, repeat this at the other carbon atom. This system is not used for cycloalkenes - If the two groups of higher priority are on the same side of the double bond, the alkene is designated Z. If the two groups of higher priority are on opposite sides of the double bond, the alkene is designated E - Hydrogenation is a syn/cis addition 7.3 - Relative Stabilities of Alkenes - The trans isomer is generally more stable than the cis isomer due to electron repulsions - The addition of hydrogen to an alkene, hydrogenation, is exothermic (heat of hydrogenation) - The greater number of attached alkyl groups, the greater the stability of an alkene 7.5 - Synthesis of Alkenes via Elimination Reactions, 7.6 - Dehydrohalogenation of Alkyl Halides How to Favor E2: - Reaction conditions that favor elimination by E1 should be avoided due to the highly competitive SN 1 mechanism - To favor E2, a secondary or tertiary alkyl halide should be used - If there is only a possibility for a primary alkyl halide, use a bulky base - Use a higher concentration of a strong and nonpolarizable base, like an alkoxide - EtONa=EtOH favors the more substituted double bond