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Clusters – Contemporary Insight in Structure and Bonding 174 Structure and Bonding
Structure and Bonding 174 Series Editor: D.M.P. Mingos Stefanie Dehnen Editor Clusters – Contemporary Insight in Structure and Bonding 174 Structure and Bonding Series Editor: D.M.P. Mingos, Oxford, United Kingdom Editorial Board: X. Duan, Beijing, China L.H. Gade, Heidelberg, Germany Y. Lu, Urbana, IL, USA F. Neese, Mulheim€ an der Ruhr, Germany J.P. Pariente, Madrid, Spain S. Schneider, Gottingen,€ Germany D. Stalke, Go¨ttingen, Germany Aims and Scope Structure and Bonding is a publication which uniquely bridges the journal and book format. Organized into topical volumes, the series publishes in depth and critical reviews on all topics concerning structure and bonding. With over 50 years of history, the series has developed from covering theoretical methods for simple molecules to more complex systems. Topics addressed in the series now include the design and engineering of molecular solids such as molecular machines, surfaces, two dimensional materials, metal clusters and supramolecular species based either on complementary hydrogen bonding networks or metal coordination centers in metal-organic framework mate- rials (MOFs). Also of interest is the study of reaction coordinates of organometallic transformations and catalytic processes, and the electronic properties of metal ions involved in important biochemical enzymatic reactions. Volumes on physical and spectroscopic techniques used to provide insights into structural and bonding problems, as well as experimental studies associated with the development of bonding models, reactivity pathways and rates of chemical processes are also relevant for the series. Structure and Bonding is able to contribute to the challenges of communicating the enormous amount of data now produced in contemporary research by producing volumes which summarize important developments in selected areas of current interest and provide the conceptual framework necessary to use and interpret mega- databases. -
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 -
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. -
Oxidative Addition & Reductive Elimination
3/1/2021 Oxidative Addition & Reductive Elimination Robert H. Crabtree: Pages 159 – 182 and 235 - 266 1 Oxidative Addition Change in Example Group configuration • Oxidative addition is a key step in many transition-metal catalyzed reactions 10 8 I III • Basic reaction: d d Cu Cu 11 X X Pd0 PdII 10 LnM + LnM Pt0 PtII 10 Y Y d8 d6 PdII PdIV 10 • The new M-X and M-Y bonds are formed using the electron pair of the X-Y PtII PtIV 10 bond and one metal-centered lone pair IrI IrIII 9 RhI RhIII 9 • The metal goes up in oxidation state (+2), X-Y formally gets reduced to X-, Y- d6 d4 ReI ReIII 7 • The ease of addition (or elimination) can be tuned by the electronic and 0 II steric properties of the ancillary ligands Mo Mo 6 • OA favored by strongly e-donating L d4 d2 MoII MoIV 6 • The most common applications involve: a) Late transition metals (platinum metals: Ru, Rh, Pd, Ir, Pt) - not d7 d6 2CoII 2CoIII 9 too sensitive to O2 and H2O; routinely used in organic synthesis b) C-Halogen, H-H or Si-H bonds d4 d3 2CrII 2CrIII 6 • Common for transition metals, rare for main-group metals but: Grignard reagents! 2 1 3/1/2021 Oxidative addition – concerted mechanism Concerted addition - mostly with non-polar X-Y bonds X X X LnM + LnM LnM Y Y Y A Cr(CO)5: • H2, silanes, alkanes, ... coordinatively Cr(PMe3)5: • Arene C-H bonds more reactive than alkane C-H bonds unsaturated, but metal- centered lone pairs not phosphines are better • H-H, C-H strong bond, but M-H and M-C bonds can be very available donors, weaker acceptors full oxidative -
Oxidative Addition of Polar Reagents
OXIDATIVE ADDITION OF POLAR REAGENTS Organometallic chemistry has vastly expanded the practicing organic chemist’s notion of what makes a good nucleophile or electrophile. Pre-cross-coupling, for example, using unactivated aryl halides as electrophiles was largely a pipe dream (or possible only under certain specific circumstances). Enter the oxidative addition of polarized bonds: all of a sudden, compounds like bromobenzene started looking a lot more attractive as starting materials. Cross-coupling reactionsinvolving sp2- and sp-hybridized C–X bonds beautifully complement the “classical” substitution reactions at sp3electrophilic carbons. Oxidative addition of the C–X bond is the step that kicks off the magic of these methods. In this post, we’ll explore the mechanisms and favorability trends of oxidative additions of polar reagents. The landscape of mechanistic possibilities for polarized bonds is much more rich than in the non-polar case—concerted, ionic, and radical mechanisms have all been observed. Concerted Mechanisms 2 Oxidative additions of aryl and alkenyl Csp –X bonds, where X is a halogen or sulfonate, proceed through concertedmechanisms analogous to oxidative additions of dihydrogen. Reactions of N–H and O–H bonds in amines, alcohols, and water also appear to be concerted. A π complex involving η2-coordination is an intermediate in the mechanism of insertion into aryl halides at least, and probably vinyl halides too. As two open coordination sites are necessary for concerted oxidative addition, loss of a ligand from a saturated metal complex commonly precedes the actual oxidative addition event. Concerted oxidative addition of aryl halides and sulfonates. Trends in the reactivity of alkyl and aryl (pseudo)halides toward oxidative addition are some of the most famous in organometallic chemistry. -
Chemical Chemical Hazard and Compatibility Information
Chemical Chemical Hazard and Compatibility Information Acetic Acid HAZARDS & STORAGE: Corrosive and combustible liquid. Serious health hazard. Reacts with oxidizing and alkali materials. Keep above freezing point (62 degrees F) to avoid rupture of carboys and glass containers.. INCOMPATIBILITIES: 2-amino-ethanol, Acetaldehyde, Acetic anhydride, Acids, Alcohol, Amines, 2-Amino-ethanol, Ammonia, Ammonium nitrate, 5-Azidotetrazole, Bases, Bromine pentafluoride, Caustics (strong), Chlorosulfonic acid, Chromic Acid, Chromium trioxide, Chlorine trifluoride, Ethylene imine, Ethylene glycol, Ethylene diamine, Hydrogen cyanide, Hydrogen peroxide, Hydrogen sulfide, Hydroxyl compounds, Ketones, Nitric Acid, Oleum, Oxidizers (strong), P(OCN)3, Perchloric acid, Permanganates, Peroxides, Phenols, Phosphorus isocyanate, Phosphorus trichloride, Potassium hydroxide, Potassium permanganate, Potassium-tert-butoxide, Sodium hydroxide, Sodium peroxide, Sulfuric acid, n-Xylene. Acetone HAZARDS & STORAGE: Store in a cool, dry, well ventilated place. INCOMPATIBILITIES: Acids, Bromine trifluoride, Bromine, Bromoform, Carbon, Chloroform, Chromium oxide, Chromium trioxide, Chromyl chloride, Dioxygen difluoride, Fluorine oxide, Hydrogen peroxide, 2-Methyl-1,2-butadiene, NaOBr, Nitric acid, Nitrosyl chloride, Nitrosyl perchlorate, Nitryl perchlorate, NOCl, Oxidizing materials, Permonosulfuric acid, Peroxomonosulfuric acid, Potassium-tert-butoxide, Sulfur dichloride, Sulfuric acid, thio-Diglycol, Thiotrithiazyl perchlorate, Trichloromelamine, 2,4,6-Trichloro-1,3,5-triazine -
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. -
A Novel Series of Titanocene Dichloride Derivatives: Synthesis, Characterization and Assessment of Their
A novel series of titanocene dichloride derivatives: synthesis, characterization and assessment of their cytotoxic properties by Gregory David Potter A thesis submitted to the Department of Chemistry in conformity with the requirements for the degree of Doctor of Philosophy Queen’s University Kingston, Ontario, Canada May, 2008 Copyright © Gregory David Potter, 2008 Abstract Although cis-PtCl2(NH3)2 (cisplatin) has been widely used as a chemotherapeutic agent, its use can be accompanied by toxic side effects and the development of drug resistance. Consequently, much research has been focused on the discovery of novel transition metal compounds which elicit elevated cytotoxicities coupled with reduced toxic side effects and non-cross resistance. Recently, research in this lab has focused on preparing derivatives of titanocene dichloride (TDC), a highly active chemotherapeutic agent, with pendant alkylammonium groups on one or both rings. Earlier results have demonstrated that derivatives containing either cyclic or chiral alkylammonium groups had increased cytotoxic activities. This research therefore investigated a new series of TDC complexes focusing specifically on derivatives bearing cyclic and chiral alkylammonium groups. A library of ten cyclic derivatives and six chiral derivatives were synthesized and fully characterized. These derivatives have undergone in vitro testing as anti-tumour agents using human lung, ovarian, and cervical carcinoma cell lines (A549, H209, H69, H69/CP, A2780, A2780/CP and HeLa). These standard cell lines represent solid tumour types for which new drugs are urgently needed. The potencies of all of the Ti (IV) derivatives varied greatly (range from 10.8 μM - >1000 μM), although some trends were observed. In general, the dicationic analogues exhibited greater potency than the corresponding monocationic derivatives. -
Organometallic Chemistry BASIC PRINCIPLES, APPLICATIONS, and a FEW CASE STUDIES
Safety Moment TYLER LAB GROUP MEETING 1 Safety Moment TYLER LAB GROUP MEETING 2 Metal Hydrides: Benchtop vs. Box Hydride = :H- Hydrides are powerful Lewis bases and reducing agent ◦ Exothermically form H2 (this should scare you) ◦ Heating leads to faster reactivity ◦ H evolution leads to rapid increase in pressure2 ◦ Uncontrolled reactions easily cause runaway exotherm, class D fire, explosion, and death/unemployment LiAlH is the #1 chemical cause of fatality in chemical4 industry 3 Metal Hydrides: “I want to commit the murder I was imprisoned for†.” LiAlH4 ◦ Insanely irritating (serious safety hazard) ◦ Extremely moisture sensitive (don’t leave out for >2 minutes) ◦ Ethereal mixtures are pyrophoric! DiBuAl-H ◦ Pyrophoric – it will explode upon exposure to oxygen NaEt3BH ◦ Pyrophoric in solution LiH and NaH ◦ Can be handled on the benchtop (not >2 minutes) ◦ Parrafin oil dispersions much safer KH ◦ Pyrophoric if not in a dispersion ◦ Handle with extreme care! † Sirius Black, Harry Potter and the Prisoner of Azkaban 4 Metal Hydrides: “I want to commit the murder I was imprisoned for†.” CaH2 ◦ Very safe to handle on the benchtop Pt-H, Pd-H, Ni-H ◦ All very pyrophoric NaBH4 ◦ Very safe in general Other hydrides ◦ Treat as pyrophoric ◦ Transition metal hydrides vary in hydridic strength ◦ General rule of thumb: if it does hydrogenations, it is probably pyrophoric ◦ If they’re in organics of any kind, they are probably pyrophoric † Sirius Black, Harry Potter and the Prisoner of Azkaban 5 Organometallic Chemistry BASIC PRINCIPLES, APPLICATIONS, -
Neutral All Metal Aromatic Half-Sandwich Complexes Between Alkaline Earth and Transition Metals: an Ab-Initio Exploration
Neutral All Metal Aromatic Half-Sandwich Complexes Between Alkaline Earth and Transition Metals: An Ab-initio Exploration Amlan Jyoti Kalita Cotton University Prem Prakash Sahu Cotton University Ritam Raj Borah Gauhati University Shahnaz Sultana Rohman Cotton University Chayanika Kashyap Cotton University Sabnam Swabaka Ullah Cotton University Indrani Baruah Cotton University Lakhya Jyoti Mazumder Cotton University Dimpul Konwar Gachon University Ankur Kanti Guha ( [email protected] ) Cotton University https://orcid.org/0000-0003-4370-8108 Research Article Keywords: Half-sandwich complexes, dual aromaticity, topological analyses Posted Date: May 24th, 2021 DOI: https://doi.org/10.21203/rs.3.rs-505446/v1 License: This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License Page 1/13 Version of Record: A version of this preprint was published at Structural Chemistry on July 7th, 2021. See the published version at https://doi.org/10.1007/s11224-021-01807-w. Page 2/13 Abstract Sandwich complexes nd their interests among the chemists after the breakthrough discovery of ferrocene. Since then, a number of sandwich and half sandwich complexes were predicted and synthesized. Herein, we have theoretically proposed a series of half-sandwich complexes involving a neutral Be3 ring and transition metal. Quantum chemical calculations have shown that the proposed complexes are quite stable involving high bond dissociation energies. The thermodynamics of their formation is also favorable. The Be3 ring in all cases posses dual aromaticity which has been ascertained based on magnetic as well as topological feature of electron density. Introduction Discovery of the rst sandwich complex (C5H5)2Fe, commonly known as “ferrocene”, drew the attention of the chemistry fraternity in no time [1–3]. -
Catalysis Science & Technology
Catalysis Science & Technology Accepted Manuscript 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. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it 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/catalysis Page 1 of 6 CatalysisPlease doScience not adjust & Technology margins Journal Name ARTICLE Hydrophenylation of internal alkynes with boronic acids catalysed by a Ni-Zn hydroxy double salt-intercalated Received 00th January 20xx, Accepted 00th January 20xx Manuscript DOI: 10.1039/x0xx00000x anionic rhodium(III) complex www.rsc.org/ Takayoshi Hara, 1 Nozomi Fujita, 1 Nobuyuki Ichikuni, 1 Karen Wilson, 2 Adam F. Lee, 2 and Shogo Shimazu* 1 3- [Rh(OH) 6] intercalated Ni–Zn mixed basic salts (Rh/NiZn) are efficient catalysts for the hydrophenylation of internal alkynes with arylboronic acids under mild conditions.