Homogeneous Catalysis by Cobalt and Manganese Pincer Complexes

ACS Catalysis, Journal Year: 2018, Volume and Issue: 8(12), P. 11435 - 11469

Published: Oct. 16, 2018

Homogeneous catalysis of organic transformations by metal complexes has been mostly based on noble metals. In recent years, tremendous progress made in the field base-metal catalysis, with pincer-type complexes, such as iron, cobalt, nickel, and manganese pincer systems. Particularly impressive is explosive growth Mn-based first being reported recently 2016. This review covers homogeneously catalyzed reactions using cobalt manganese. Various are described, including acceptorless dehydrogenation, hydrogenation, dehydrogenative coupling, hydrogen borrowing, transfer, H–X additions, C–C alkene polymerization N2 fixation, their scope brief mechanistic comments.

Language: Английский

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Key factors in pincer ligand design

Chemical Society Reviews, Journal Year: 2018, Volume and Issue: 47(6), P. 1959 - 1968

Published: Jan. 1, 2018

Pincers, tridentate ligands that prefer a meridional geometry, are rising class because of their distinctive combination properties. They permit good level control on the nature coordination sphere by holding donor groups in predictable arrangement. Some groups, such as an aryl or pyridine, would normally be easily lost monodentate ligands, become reliably coordinated, especially if they form central unit three. Many pincer complexes show exceptional thermal stability, property is particularly prized homogeneous catalysis where can high temperature operation. The connectors between three often rigid, enforcing strict mer geometry but flexible linkers fac binding and even fluxionality two forms. Rigid pincers make for asymmetric catalysis-if wingtip cannot rotate may instead maintain which suitable substituents project into active site area catalyst help enantio-differentiation relevant transition states. Examples have been selected to illustrate these other properties this promising ligand class.

Language: Английский

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Homogeneous Catalysis for Sustainable Energy: Hydrogen and Methanol Economies, Fuels from Biomass, and Related Topics

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(1), P. 385 - 441

Published: Nov. 2, 2021

As the world pledges to significantly cut carbon emissions, demand for sustainable and clean energy has now become more important than ever. This includes both production storage of carriers, a majority which involve catalytic reactions. article reviews recent developments homogeneous catalysts in emerging applications energy. The most focus been on hydrogen as several efficient have reported recently (de)hydrogenative transformations promising economy. Another direction that extensively covered this review is methanol Homogeneous investigated from CO

Language: Английский

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Bimetallic Sites for Catalysis: From Binuclear Metal Sites to Bimetallic Nanoclusters and Nanoparticles

Chemical Reviews, Journal Year: 2023, Volume and Issue: 123(8), P. 4855 - 4933

Published: March 27, 2023

Heterogeneous bimetallic catalysts have broad applications in industrial processes, but achieving a fundamental understanding on the nature of active sites at atomic and molecular level is very challenging due to structural complexity catalysts. Comparing features catalytic performances different entities will favor formation unified structure-reactivity relationships heterogeneous thereby facilitate upgrading current In this review, we discuss geometric electronic structures three representative types (bimetallic binuclear sites, nanoclusters, nanoparticles) then summarize synthesis methodologies characterization techniques for entities, with emphasis recent progress made past decade. The supported nanoparticles series important reactions are discussed. Finally, future research directions catalysis based and, more generally, prospective developments both practical applications.

Language: Английский

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The continuum of carbon–hydrogen (C–H) activation mechanisms and terminology

Communications Chemistry, Journal Year: 2021, Volume and Issue: 4(1)

Published: Dec. 10, 2021

Abstract As a rapidly growing field across all areas of chemistry, C-H activation/functionalisation is being used to access wide range important molecular targets. Of particular interest the development sustainable methodology for alkane functionalisation as means reducing hydrocarbon emissions. This Perspective aims give an outline community with respect commonly terminology in activation, well mechanisms that are currently understood operate (cyclo)alkane activation/functionalisation.

Language: Английский

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Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(40), P. 16470 - 16485

Published: Sept. 30, 2021

The value of catalytic dehydrogenation aliphatics (CDA) in organic synthesis has remained largely underexplored. Known homogeneous CDA systems often require the use sacrificial hydrogen acceptors (or oxidants), precious metal catalysts, and harsh reaction conditions, thus limiting most existing methods to non- or low-functionalized alkanes. Here we describe a visible-light-driven, dual-catalyst system consisting inexpensive organophotoredox base-metal catalysts for room-temperature, acceptorless-CDA (Al-CDA). Initiated by photoexited 2-chloroanthraquinone, process involves H atom transfer (HAT) form alkyl radicals, which then react with cobaloxime produce olefins H2. This operationally simple method enables direct readily available chemical feedstocks diversely functionalized olefins. For example, demonstrate, first time, oxidant-free desaturation thioethers amides alkenyl sulfides enamides, respectively. Moreover, system's exceptional site selectivity functional group tolerance are illustrated late-stage 14 biologically relevant molecules pharmaceutical ingredients. Mechanistic studies have revealed dual HAT provided insights into origin reactivity selectivity.

Language: Английский

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Catalytic Chemical Recycling of Post-Consumer Polyethylene

Journal of the American Chemical Society, Journal Year: 2022, Volume and Issue: 144(51), P. 23280 - 23285

Published: Dec. 16, 2022

Among commercial plastics, polyolefins are the most widely produced worldwide but have limited recyclability. Here, we report a chemical recycling route for conversion of post-consumer high-density polyethylene (HDPE) into telechelic macromonomers suitable circular reprocessing. Unsaturation was introduced HDPE by catalytic dehydrogenation using an Ir-POCOP catalyst without alkene acceptor. Cross-metathesis with 2-hydroxyethyl acrylate followed hydrogenation transformed partially unsaturated macromonomers. The direct repolymerization gave brittle material due to low overall weight-average molecular weight. Aminolysis small amount diethanolamine increased functionality. resulting were repolymerized through transesterification generate polymer comparable mechanical properties starting waste. Depolymerization catalyzed organic base regenerated macromonomers, thereby allowing waste materials enter pathway.

Language: Английский

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Paired Oxidative and Reductive Catalysis: Breaking the Potential Barrier of Electrochemical C(sp³)−H Alkenylation**

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(24)

Published: April 1, 2023

Due to the intrinsic inertness of alkanes, strong oxidative conditions are typically required enable their C(sp3 )-H functionalization. Herein, a paired electrocatalysis strategy was developed by integrating catalysis with reductive in one cell without interference, which earth-abundant iron and nickel employed as anodic cathodic catalysts, respectively. This approach lowers previously high oxidation potential for alkane activation, enabling electrochemical functionalization at ultra-low ≈0.25 V vs. Ag/AgCl under mild conditions. Structurally diverse alkenes, including challenging all-carbon tetrasubstituted olefins, can be accessed using readily available alkenyl electrophiles.

Language: Английский

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Transfer Hydrogenation of Alkenes Using Ethanol Catalyzed by a NCP Pincer Iridium Complex: Scope and Mechanism

Journal of the American Chemical Society, Journal Year: 2018, Volume and Issue: 140(12), P. 4417 - 4429

Published: March 8, 2018

The first general catalytic approach to effecting transfer hydrogenation (TH) of unactivated alkenes using ethanol as the hydrogen source is described. A new NCP-type pincer iridium complex (BQ-NCOP)IrHCl containing a rigid benzoquinoline backbone has been developed for efficient, mild TH C–C multiple bonds with ethanol, forming ethyl acetate sole byproduct. wide variety alkenes, including multisubstituted alkyl aryl and heteroatom-substituted well O- or N-containing heteroarenes internal alkynes, are suitable substrates. Importantly, (BQ-NCOP)Ir/EtOH system exhibits high chemoselectivity alkene in presence reactive functional groups, such ketones carboxylic acids. Furthermore, reaction C2D5OD provides convenient route deuterium-labeled compounds. Detailed kinetic mechanistic studies have revealed that monosubstituted (e.g., 1-octene, styrene) cyclooctene (COE)) exhibit fundamental difference. OH group displays normal isotope effect (KIE) styrene, but substantial inverse KIE case COE. catalysis styrene 1-octene relatively strong binding affinity Ir(I) center (BQ-NCOP)IrI(alkene) adduct an off-cycle catalyst resting state, rate law shows positive order EtOH, first-order catalyst. In contrast, COE state (BQ-NCOP)IrIII(H)[O(Et)···HO(Et)···HOEt] features six-membered iridacycle consisting two hydrogen-bonds between one EtO ligand EtOH molecules, which coordinated Ir(III) center. negative zeroth-order COE, observed corresponds equilibrium pre-equilibrium formation (BQ-NCOP)IrIII(H)(OEt) from via dissociation. Regardless substrate, dehydrogenation slow segment cycle, while occurs readily following rate-determining step, is, β-hydride elimination (BQ-NCOP)Ir(H)(OEt) form (BQ-NCOP)Ir(H)2 acetaldehyde. latter effectively converted innocent under conditions, thus avoiding poisoning iridium-mediated decarbonylation

Language: Английский

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PN³(P)-Pincer Complexes: Cooperative Catalysis and Beyond

ACS Catalysis, Journal Year: 2019, Volume and Issue: 9(3), P. 1619 - 1629

Published: Jan. 11, 2019

ADVERTISEMENT RETURN TO ISSUEPREVViewpointNEXTPN3(P)-Pincer Complexes: Cooperative Catalysis and BeyondHuaifeng LiHuaifeng LiKAUST Center Division of Physical Sciences Engineering, King Abdullah University Science Technology, Thuwal 23955-6900, Saudi ArabiaMore by Huaifeng Li, Théo P. GonçalvesThéo GonçalvesKAUST Gonçalves, Daniel LuppDaniel LuppKAUST Lupp, Kuo-Wei Huang*Kuo-Wei HuangKAUST Arabia*E-mail: [email protected]More Huanghttp://orcid.org/0000-0003-1900-2658Cite this: ACS Catal. 2019, 9, 3, 1619–1629Publication Date (Web):January 11, 2019Publication History Received8 November 2018Published online11 January 2019Published inissue 1 March 2019https://pubs.acs.org/doi/10.1021/acscatal.8b04495https://doi.org/10.1021/acscatal.8b04495editorialACS PublicationsCopyright © 2019 American Chemical Society. This publication is available under these Terms Use. Request reuse permissions free to access through this site. Learn MoreArticle Views8541Altmetric-Citations89LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum full text article downloads since 2008 (both PDF HTML) across all institutions individuals. These metrics regularly updated reflect usage leading up last few days.Citations number other articles citing article, calculated Crossref daily. Find more information about citation counts.The Altmetric Attention Score a quantitative measure attention that research has received online. Clicking on donut icon will load page at altmetric.com with additional details score social media presence for given article. how calculated. Share Add toView InAdd Full Text ReferenceAdd Description ExportRISCitationCitation abstractCitation referencesMore Options onFacebookTwitterWechatLinked InRedditEmail (2 MB) Get e-AlertscloseSUBJECTS:Catalysts,Ligands,Metals,Pincer complexes,Reactivity e-Alerts

Language: Английский

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