Small Molecule Activation and Catalysis by a Cobalt N-heterocyclic Phosphido Complex PDF Download
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Author: Andrew M. Poitras
Publisher:
ISBN:
Category : Cobalt
Languages : en
Pages : 164
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Book Description
Due to both environmental and economic concerns, there is a demand for the development of more sustainable catalysts and the low cost and greater availability of late first row transition metals make them ideal candidates to replace currently used precious metals. However, one of the main challenges with base metals is the ability to promote two-electron processes needed for most catalytic reactions. Metal-ligand cooperativity has emerged as a viable strategy for promoting s-bond activation. The ligand can participate in two potential ways, ligand-based redox activity or by direct ligand involvement in the s-bond cleavage events, which eliminates the redox requirements of the metal center. N-heterocyclic phosphenium/phosphido ligands (NHP+/-) with chelating diphosphine sidearms can enforce coordination to metal centers while imparting stability on the resulting complex. When incorporated in the tridentate framework (PPP), the NHP+ can be reduced to the anionic NHP- form, which can allow for ligand-based redox processes. This dissertation is focused on the recent exploration of the structural and reactivity studies of cobalt complexes bearing a tridentate ligand with a central NHP+/- moiety. The metal-ligand cooperativity of the cobalt NHP+/- complexes is explored through the rich redox profiles of the monomers and dimers and through the activation of various E-H bonds (E = H, O, S) across the cobalt-PNHP bond. In addition, a highly selective catalytic system for the hydroboration of alkenes is successfully developed using a cobalt NHP+/- complex.
Author: Andrew M. Poitras
Publisher:
ISBN:
Category : Cobalt
Languages : en
Pages : 164
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Book Description
Due to both environmental and economic concerns, there is a demand for the development of more sustainable catalysts and the low cost and greater availability of late first row transition metals make them ideal candidates to replace currently used precious metals. However, one of the main challenges with base metals is the ability to promote two-electron processes needed for most catalytic reactions. Metal-ligand cooperativity has emerged as a viable strategy for promoting s-bond activation. The ligand can participate in two potential ways, ligand-based redox activity or by direct ligand involvement in the s-bond cleavage events, which eliminates the redox requirements of the metal center. N-heterocyclic phosphenium/phosphido ligands (NHP+/-) with chelating diphosphine sidearms can enforce coordination to metal centers while imparting stability on the resulting complex. When incorporated in the tridentate framework (PPP), the NHP+ can be reduced to the anionic NHP- form, which can allow for ligand-based redox processes. This dissertation is focused on the recent exploration of the structural and reactivity studies of cobalt complexes bearing a tridentate ligand with a central NHP+/- moiety. The metal-ligand cooperativity of the cobalt NHP+/- complexes is explored through the rich redox profiles of the monomers and dimers and through the activation of various E-H bonds (E = H, O, S) across the cobalt-PNHP bond. In addition, a highly selective catalytic system for the hydroboration of alkenes is successfully developed using a cobalt NHP+/- complex.
Author: Ming Li
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Dinuclear complexes based on this two-in-one pincer ligand scaffold have exhibited fascinating magnetic properties and promise high reactivity in catalysis and small molecule activation. In this thesis, the main objective is to accomplish small molecule activation using dinuclear cobalt complexes as precursors and isolate important intermediate complexes for better understanding the possible mechanisms of small molecule activation. More specifically, this thesis work can be divided into five parts: N2 fixation and catalytic conversion of N2 (Chapters 2 and 3), the formation of diazene compl...
Author: Marko Hapke
Publisher: John Wiley & Sons
ISBN: 3527344500
Category : Technology & Engineering
Languages : en
Pages : 480
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Book Description
Provides a much-needed account of the formidable "cobalt rush" in organic synthesis and catalysis Over the past few decades, cobalt has turned into one of the most promising metals for use in catalytic reactions, with important applications in the efficient and selective synthesis of natural products, pharmaceuticals, and new materials. Cobalt Catalysis in Organic Synthesis: Methods and Reactions provides a unique overview of cobalt-catalysed and -mediated reactions applied in modern organic synthesis. It covers a broad range of homogeneous reactions, like cobalt-catalysed hydrogenation, hydrofunctionalization, cycloaddition reactions, C-H functionalization, as well as radical and biomimetic reactions. First comprehensive book on this rapidly evolving research area Covers a broad range of homogeneous reactions, such as C-H activation, cross-coupling, synthesis of heterocyclic compounds (Pauson-Khand), and more Chapters on low-valent cobalt complexes as catalysts in coupling reactions, and enantioselective cobalt-catalyzed transformations are also included Can be used as a supplementary reader in courses of advanced organic synthesis and organometallic chemistry Cobalt Catalysis in Organic Synthesis is an ideal book for graduates and researchers in academia and industry working in the field of synthetic organic chemistry, catalysis, organometallic chemistry, and natural product synthesis.
Author: Rodolphe Fouad Rene Jazzar
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: R. Morris Bullock
Publisher: John Wiley & Sons
ISBN: 3527632409
Category : Science
Languages : en
Pages : 296
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Book Description
Written for chemists in industry and academia, this ready reference and handbook summarizes recent progress in the development of new catalysts that do not require precious metals. The research thus presented points the way to how new catalysts may ultimately supplant the use of precious metals in some types of reactions, while highlighting the remaining challenges. An essential copanion for organic and catalytic chemists, as well as those working with/on organometallics and graduate students. From the contents: * Catalysis Involving the H' Transfer Reactions of First-Row Transition Metals * Catalytic Reduction of Dinitrogen to Ammonia by Molybdenum Complexes * Molybdenum and Tungsten Catalysts for Hydrogenation, Hydrosilylation and Hydrolysis * Iron in Catalytic Alkene and Carbonyl Hydrogenation Reactions * Olefin Oligomerizations and Polymerizations Catalyzed by Iron and Cobalt Complexes * Cobalt and Nickel Catalyzed Reactions Involving C-H and C-N Activation Reactions * Development of Molecular Electrocatalysts for H2 Oxidation and Production Based on Inexpensive Metals * Nickel-Catalyzed Reductinve Couplings and Cyclizations * Copper-Catalyzed Ligand Promoted Ullmann-Type Coupling Reactions * Copper-Catalyzed Azide-Alkyne Cycloaddition * "Frustrated Lewis Pairs": A Metal-Free Strategy for Hydrogenation Catalysis
Author: Minh Tho Nguyen
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The work described in this thesis is focused on the preparation of a series of novel main group complexes, featuring unusual structural and bonding situations, and the study of their reactivity toward small molecules. The new zinc complexes dimphZnBu (V-2) and dimphZnCl2Li(THF)3 (V-3), supported by a diiminophenyl (dimph) ligand were prepared. The reaction of complex V-3 with LiHBEt3 resulted in hydride transfer to the C=N imine group to give an unusual zinc dimer (V-7). The latter transformation occurs via formation of compound (ɳ1(C),ĸ1(N)- 2,6-(2,6-iPr2C6H3N=CH)2C6H3)2Zn (V-5) which can be also accessed by reduction of V-7 with KC8. Diiminophenyl (dimph) proved to be an excellent ligand platform to stabilise a low-valent phosphorus centre. The resultant compound dimphP (VI-2), which can be rationalised as an imino-stabilised phosphinidene or benzoazaphopshole, shows remarkable chemical stability toward water and oxygen. VI-2 reacts with excess strong acid HCl to generate the P(III) chloride (dimHph)PCl (VI-6). Surprisingly, substitution of the chloride under some nucleophilic (KOBut) and electrophilic conditions (Me3SiOTf) regenerates the parent compound VI-2 by proton removal from the weakly acidic CH2N position. A related species (dimH2ph)P (VI-10) is produced upon thermal rearrangement of the hydride (dimHph)PH (VI-9). The molecular structure and reactivity of compounds VI-2 and other related compounds are also discussed. The reduction of the O,C,O-chelated phosphorus (III) chloride (VI-16) ( O,C,O = 2,6-bis[(2,6-diisopropyl)phenoxyl]phenyl) with KC8 or PMe3 resulted in the formation of a cyclic three-membered phosphorus compound (VI-18). The intermediacy of phosphinidene VI-17 was confirmed by trapping experiments and a VT 31P{1H} NMR study. The reaction of in-situ generated phosphinidene with either PhSiH3 or HBpin resulted in the formation of an unprecedented phosphine (VI-23). The treatment of VI-16 with two equivalents of DippNHC carbene led to ArP(Cl)NHC product (VI-24). The germylone dimNHCGe (dimNHC = diimino N-Heterocyclic Carbene, VII-8) was successfully prepared by the reduction of germanium cation (VII-7) with KC8. The molecular structure of VII-8 was unambiguously established, using NMR spectroscopy and single-crystal X-ray diffraction analysis. The reactivity of VII-8 was investigated. VII-8 is inactive towards butadiene but undergoes an oxidative cyclization with tetrachloro-o-benzoquinone to give a tetragermanium derivative. VII-8 undergoes oxidation addition of CH3I and PhI, followed by an unusual migration of the Me and Ph groups from germanium to the carbene ligand. Related chemistry takes place upon protonation with dry HCl, which results in the migration of the hydride to the carbene ligand.
Author: Silvia Diez-Gonzalez
Publisher: Royal Society of Chemistry
ISBN: 1782626816
Category : Science
Languages : en
Pages : 637
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Book Description
In less than 20 years N-heterocyclic carbenes (NHCs) have become well-established ancillary ligands for the preparation of transition metal-based catalysts. This is mainly due to the fact that NHCs tend to bind strongly to metal centres, avoiding the need of excess ligand in catalytic reactions. Also, NHC‒metal complexes are often insensitive to air and moisture, and have proven remarkably resistant to oxidation. This book showcases the wide variety of applications of NHCs in different chemistry fields beyond being simple phosphine mimics. This second edition has been updated throughout, and now includes a new chapter on NHC‒main group element complexes. It covers the synthesis of NHC ligands and their corresponding metal complexes, as well as their bonding and stereoelectronic properties and applications in catalysis. This is complemented by related topics such as organocatalysis and biologically active complexes. Written for organic and inorganic chemists, this book is ideal for postgraduates, researchers and industrialists.
Author: David Morales-Morales
Publisher: Elsevier
ISBN: 0080545157
Category : Science
Languages : en
Pages : 467
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Book Description
Pincer complexes are formed by the binding of a chemical structure to a metal atom with at least one carbon-metal bond. Usually the metal atom has three bonds to a chemical backbone, enclosing the atom like a pincer. The resulting structure protects the metal atom and gives it unique properties.The last decade has witnessed the continuous growth in the development of pincer complexes. These species have passed from being curiosity compounds to chemical chameleons able to perform a wide variety of applications. Their unique metal bound structures provide some of the most active catalysts yet known for organic transformations involving the activation of bonds. The Chemistry of Pincer Compounds details use of pincer compounds including homogeneous catalysis, enantioselective organic transformations, the activation of strong bonds, the biological importance of pincer compounds as potential therapeutic or pharmaceutical agents, dendrimeric and supported materials.* Describes the chemistry and applications of this important class of organometallic and coordination compounds* Covers the areas in which pincer complexes have had an impact* Includes information on more recent and interesting pincer compounds not just those that are well-known
Author: Gerard van Koten
Publisher: Springer
ISBN: 3642310818
Category : Science
Languages : en
Pages : 363
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Book Description
Gerard van Koten: The Mono-anionic ECE-Pincer Ligand - a Versatile Privileged Ligand Platform: General Considerations.- Elena Poverenov, David Milstein: Non-Innocent Behavior of PCP and PCN Pincer Ligands of Late Metal Complexes.- Dean M. Roddick: Tuning of PCP Pincer Ligand Electronic and Steric Properties.- Gemma R. Freeman, J. A. Gareth Williams: Metal Complexes of Pincer Ligands: Excited States, Photochemistry, and Luminescence.- Davit Zargarian, Annie Castonguay, Denis M. Spasyuk: ECE-Type Pincer Complexes of Nickel.- Roman Jambor and Libor Dostál: The Chemistry of Pincer Complexes of 13 - 15 Main Group Elements.- Kálmán J. Szabo: Pincer Complexes as Catalysts in Organic Chemistry.- Jun-ichi Ito and Hisao Nishiyama: Optically Active Bis(oxazolinyl)phenyl Metal Complexes as Multi-potent Catalysts.- Anthony St. John, Karen I. Goldberg, and D. Michael Heinekey: Pincer Complexes as Catalysts for Amine Borane Dehydrogenation.- Dmitri Gelman and Ronit Romm: PC(sp3)P Transition Metal Pincer Complexes: Properties and Catalytic Applications.- Jennifer Hawk and Steve Craig: Physical Applications of Pincer Complexes.
Author: Frank Glorius
Publisher: Springer
ISBN: 3540369309
Category : Science
Languages : en
Pages : 240
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Book Description
In this book leading experts have surveyed major areas of application of NHC metal complexes in catalysis. The authors have placed a special focus on nickel- and palladium-catalyzed reactions, on applications in metathesis reactions, on oxidation reactions and on the use of chiral NHC-based catalysts. This compilation is rounded out by an introductory chapter and a chapter dealing with synthetic routes to NHC metal complexes.
