Download or read book Synthesis and Initial Reactivity Studies of Nickel Complexes on a Pincer Scaffold written by Huy Dao and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalytic oxidation reactions are prevalent in the chemical industry. The catalysts are often made with expensive metals and the mechanism(s) by which they operate are not well known. Studies of small molecules can lead to better understanding of mechanisms and thus lead to better catalysis design. Work has also been performed in designing catalysts using less costly metals. Nickel is one such metal, as it is a congener of platinum and palladium, two costly metals used widely in catalysis. Ligands can be altered to influence electronic and steric properties of the metal complexes, thus affecting catalytic activity. This thesis addresses the modification of an SCS pincer ligand and the synthesis of new nickel-SCS pincer complexes. Pincers are tridentate ligands that bind at adjacent coplanar sites. The designation "SCS" refers to the atoms at the coordination sites. The nickel-pincer complexes in this work are built from 2,6- bis(alkylthiomethyl)bromobenzene skeletons, with the alkyl groups being altered. The work presented herein describes the synthesis and characterization of Ni(SCSiPr)Br, Ni(SCStBu)Br, Ni(SCSMe)OPh, and Ni(SCSMe)Me. The reactivity of Ni(SCSMe)Me was studied and found to form Ni(SCSMe)OPh when reacted with phenol. This showed that Ni(SCSMe)Me was able to deprotonate an acidic species to form a new complex. Ni(SCSMe)Me was also found to catalyze the oxidation of triphenylphosphine to triphenylphosphine oxide when dry O2 was introduced. Eight to ten turnovers were observed.

Download or read book Nickel and Iridium Pincer Complexes with Saturated Frameworks written by and published by . This book was released on 2014 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Pincer Compounds written by David Morales-Morales and published by Elsevier. This book was released on 2018-04-11 with total page 756 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pincer Compounds: Chemistry and Applications offers valuable state-of-the-art coverage highlighting highly active areas of research—from mechanistic work to synthesis and characterization. The book focuses on small molecule activation chemistry (particularly H2 and hydrogenation), earth abundant metals (such as Fe), actinides, carbene-pincers, chiral catalysis, and alternative solvent usage. The book covers the current state of the field, featuring chapters from renowned contributors, covering four continents and ranging from still-active pioneers to new names emerging as creative strong contributors to this fascinating and promising area. Over a decade since the publication of Morales-Morales and Jensen’s The Chemistry of Pincer Compounds (Elsevier 2007), research in this unique area has flourished, finding a plethora of applications in almost every single branch of chemistry—from their traditional application as very robust and active catalysts all the way to potential biological and pharmaceutical applications. Describes the chemistry and applications of this important class of organometallic and coordination compounds Includes contributions from global leaders in the field, featuring pioneers in the area as well as emerging experts conducting exciting research on pincer complexes Highlights areas of promising and active research, including small molecule activation, earth abundant metals, and actinide chemistry

Download or read book The Chemistry of Pincer Compounds written by David Morales-Morales and published by Elsevier. This book was released on 2011-08-11 with total page 467 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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

Download or read book Synthesis Characterization and Reactivity of Nickel Complexes with N Donor Olefinic and Macrocyclic Ligands written by Lars Valentin and published by . This book was released on 2014 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nickel II Pincer Complexes Supported by 2 6 Bis 3 5 Ditolyl 2 Pyrrolyl Pyridine written by Abhijit Pramanik and published by . This book was released on 2015 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ni(II) pincer complexes are among the most important and useful compounds in homogeneous catalysis. Significant advancement has been made in this field in recent years. Many Ni(II) pincer complexes have been prepared and utilized in various catalytic reactions e.g. cross coupling reactions, C-H activation, carbon dioxide activation etc. Still, nickel(II) complexes supported by the pincer ligand with three nitrogen donors are relatively less explored and catalytic applications with those complexes are scarce in literature. This thesis describes the synthesis of a new pyrrolyl pyridine based pincer ligand and its Ni(II) complexes. The pyrrolyl pyridine pincer ligand, a relatively new class of dianionic, tridentate, nitrogen-based ligands in coordination chemistry, was prepared starting with a modified method for the synthesis of pyrrolyl pyridine. This modified procedure is simpler, less time consuming making it cheaper than the classical method and provides 2,6-bis(3,5-ditolyl-2-pyrrolyl)pyridine in good yields. Reaction of its potassium salt with Ni(OTf)2 resulted in three different stable nickel(II) pincer complexes. The novel nickel(II) pincer complexes were fully characterized by 1H NMR spectroscopy, 13C NMR spectroscopy, infrared spectroscopy and high resolution mass spectrometry. The X-ray crystal structures of the new ligand and metal complexes have been described.

Download or read book Synthesis and Structure activity Studies of Well defined Nickel Complexes as Catalysts for Cross Coupling of Alkyl Electrophiles written by and published by . This book was released on 2015 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mots-clés de l'auteur: nickel ; Kumada coupling ; Grignard reagent ; diastereoselective ; alkynylation ; Sonogashira coupling ; hemilabile ligands ; kinetics ; pincer ligands ; alkyl electrophiles.

Download or read book Homogeneous Catalysis of Nickel Hydride Complexes Bearing a Bis phosphinite Pincer Ligand written by Sumit Chakraborty and published by . This book was released on 2012 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation is focused on the synthesis of well-defined nickel hydride complexes bearing a bis(phosphinite) pincer ligand (commonly known as a POCOP ligand) and utilities of these metal complexes in varieties of useful organic transformations. Aldehydes insert cleanly and selectively into the Ni-H bonds of (POCOP)NiH complexes to form nickel alkoxide complexes. These nickel alkoxide compounds further react with phenylsilane to regenerate (POCOP)NiH and produce silyl ethers. Based on these observations, an efficient and chemoselective hydrosilylation process has been developed utilizing nickel hydrides as catalysts. The process is highly compatible with varieties of functional groups in aldehydes. A nickel hydride complex with smaller substituents on the POCOP ligand proves to be more effective hydrosilylation catalyst. In case of ketones, partial hydrosilylation occurs. (POCOP)NiH complexes also react with CO2 to produce nickel formate complexes. When stoichiometric amounts of boranes are used, nickel hydrides are cleanly reformed. The use of catalytic amounts of nickel hydrides and excess of boranes reduces CO2 to the corresponding methanol derivatives. The initial reduction products can be further hydrolyzed to yield methanol. The overall transformation is comprised of three catalytic cycles. A catalyst with more bulky substituents on the phosphorus atoms of pincer ligand is a more effective catalyst than those containing smaller substituents. This phenomenon has been rationalized by invoking more favorable dihydridoborate adduct formation between less bulky nickel hydrides and boranes. One of such dihydridoborate adduct has been successfully isolated and its influence on the catalytic CO2 reduction has been demonstrated. (POCOP)NiH complexes have been found be active catalysts for the decomposition of formic acid to release dihydrogen. When the kinetics the reaction is monitored by in-situ IR spectroscopy, a unique sigmoidal pattern is observed. Several mechanistic possibilities such as heterogeneity, cooperativity, and formation of other reactive intermediates have been experimentally tested to understand the unusual kinetic behavior. A mechanistic investigation pertaining to NiH-catalyzed isomerization of terminal olefins such as 1-butene has been carried out. Two major pathways for olefin isomerization reaction, namely (a) metal hydride addition-elimination and (b) p-allyl metal hydride have been ruled out on the basis of reactivity studies of branched nickel butyl complex and labeling experiments. An H-atom transfer pathway has been proposed based on the radical inhibitor studies. In addition to the olefin isomerization, the branched nickel butyl complex isomerizes to the linear nickel butyl complex possibly via a unique intramolecular pathway. Nickel hydrides efficiently catalyze the cyanomethylation of aldehydes to produce ß-hydroxy nitriles. This reaction does not require an external base which is mandatory for other related systems. The (POCOP)Ni-CH2CN complex, a potential intermediate in this reaction, has been isolated and characterized. This compound reacts directly with benzaldehyde to produce the ß-hydroxy nitrile. The nickel alkoxide complexes that result from the insertion reaction between nickel hydrides and aldehydes, act as internal bases in this system. Varieties of aldehydes including base-sensitive aldehydes have been successfully coupled with acetonitrile using nickel hydride catalysts.

Download or read book Organometallic Pincer Chemistry written by Gerard van Koten and published by Springer. This book was released on 2012-09-17 with total page 363 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Nickel Catalysis and Coordination Chemistry written by Yahya Albkuri and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Different metals and metal complexes have been used as catalysts in many industries such as commodity petrochemicals, fine and specialty chemicals, polymers, environmental services, agrochemicals and pharmaceuticals. Although these catalysts allow for increased reaction rates and selectivity, they can also be toxic, expensive and of limited supply (cf. Pt group metals). This has led researchers to the intensive study of first row metal catalysts, with nickel standing out as the most widely studied to date. As found for other first row metal catalysts, nickel's easy access to oxidation states 0-3 allows for a number of different one- and two-electron mechanisms and novel transformations. In Chapter 2 we use a phosphine-free, tridentate N,N,N ligand to generate an active catalyst for the C-N cross-coupling reaction of aryl halides with amines. The catalyst demonstrated excellent turnover numbers (up to 484) for the amination reactions that are proposed to proceed through a Ni(I)-Ni(III) cycle. In Chapter 3 we investigate the Ni coordination chemistry of a biomimetic SNS thiolate ligand. Protonation of the Ni bis(thiolate) complex, Ni(-SNS)2, removes one SNS ligand, affording crystals of a thiolate-bridged dimer dication, {[Ni(--SNS)]2}2+ that exhibits unique anionic tridentate ligand dynamics. Dissolving these crystals, even in weakly-coordinating solvents such as dichloromethane, gives a mixture of 'naked' Ni2+ and paramagnetic, trinuclear {[Ni(--SNS)2]2Ni}2+. Although this equilibrium lies far to the right (no diamagnetic dication visible in NMR), addition of ancillary ligands proceeds smoothly to provide several mono- and dinuclear Ni thiolate products, [Ni-SNS)L]n - potential bifunctional catalysts for further studies. In Chapter 4 we demonstrate using chemical and electrochemical techniques that one-electron reduction of Ni(-SNS)2 triggers quantitative imine C-C bond coupling, forming [Ni(S2N2)]- with a redox-active ligand. Spectroelectrochemical studies indicated reversible oxidation and reduction steps give three stable redox states, ([Ni(S2N2)]0/-/2-), that were characterized by NMR, EPR and UV-Vis spectroscopy, X-ray diffraction and computational chemistry. While the Ni(0) dianion (and not the Ni(I) anion) reacted reversibly with phenol and carbon dioxide, results from Chapter 5 showed that reactions with strong electron-acceptor fluoroalkenes proceeded more cleanly with the Ni(I) anion. The latter reactions afforded a mixture of fluoroalkenyl and fluoroalkyl products resulting from C-F bond activation and electron transfer/H atom abstraction, respectively. In Chapter 6 we discuss our results in the context of the current state of the art and suggest some avenues for future development.

Download or read book Design Synthesis and DNA Reactivity of Nickel Complexes Containing DNA Binding Groups written by Ren-Hwa Yeh and published by . This book was released on 1997 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis Structure and Reactivity of Nickel nickel Complexes for Understanding the A Cluster in Acetyl Coenzyme A Synthase written by William G. Dougherty (Jr) and published by ProQuest. This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The synthesis and reactivity of a series of binuclear NiNi complexes designed to model the A cluster of Acetyl Coenzyme A Synthase (ACS) are reported. The complexes were synthesized by metathesis reactions between the diamido dithiolato complexes Ni(phmi) or Ni(phma), phmi = N, N'-1,2-phenylene-bis(2-sulfanyl-2-methylpropionamide), phma = N, N'-1,2-phenylenebis(2-mercaptoacetamide); and the phosphine complexes Ni(dRpe)Cl 2, R = phenyl, ethyl, isopropyl. The complexes were fully characterized including by X-ray diffraction analysis demonstrating both the structural and electronic effects resulting from varying the substituent on the chelating phosphine and the bridging thiolato donors. These steric and electronic effects were also evident when investigating the electrochemical properties of these complexes by cyclic voltammetry, which indicated that the compounds were able to undergo two successive one-electron reductions at the S 2 P 2 coordinated nickel site. Ni(phma)Ni(depe) was reduced chemically using Na/Hg amalgam or decamethylcobaltocene producing a mixed-valent Ni 2+ Ni 1+ binuclear complex in solution, supported by an EPR signal consistent with a Ni 1+ center coupled to two equivalent phosphorus atoms, that reacts with CO ultimately forming trinuclear [Ni3(phma)2] 2- and Ni(dppe)(CO) 2 . A series of new NiNi-Me binuclear complexes were synthesized by metathesis of K 2 [Ni(phmi)] and [Et 4 N] 2 [Ni(phma)] with the methylnickel complex, Ni(dppe)MeCl. The complexes were characterized fully and the [Et 4 N][Ni(phma)Ni(dppe)Me] derivative was characterized crystallographically. These complexes showed interesting fluxional behavior in solution, which was investigated by variable temperature NMR studies. The fluxionality is proposed to arise from the isomerization of the methylnickel fragment between the two thiolate donors of the N 2 S 2 ligand through a 5-coordinate transition state. A series of thiolate exchange reactions were performed to assess thiolate lability. When a solution of [Et 4 N][Ni(phma)Ni(dppe)Me] was exposed to 1 equivalent of K 2 [Ni(phmi)] a equimolar amount of [Ni(phmi)Ni(dppe)Me] 2- and [Ni(phma)Ni(dppe)Me] 2- are produced as monitored by NMR spectroscopy. A crossover experiment between K[Ni(phmi)Ni(dppe)Me] and [Et 4 N][Ni(phma)Ni(dppe)CD 3] was performed and resulted in an equilibrium mixture containing all four possible complexes with K eq = 1. The methyl complexes reacted with CO forming Ni-acyl species that decompose rapidly under excess CO generating an acylated (N 2 S 2) ligand. This observed thiolate lability might be relevant to the enzyme where the exchange of one of the bridging thiolates for the thiolate CoA could be part of the mechanism responsible for acyl group transfer.

Download or read book From the Reactivity of Pincer CCC Nickel Complexes to Catalysis with Simple Nickel Salts written by Gabriel Antonio Espinosa Martinez and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis Characterization and Reactivity of Various Imine Nickel II Complexes written by Daniel Beagan and published by . This book was released on 2016 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis Characterization and Reactivity of Ni II Complexes Stabilized by an Intramolecular Hydrogen Bonding Network written by Darla A. Powell-Jia and published by . This book was released on 2010 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metalloenzymes are able to perform a wide variety of difficult chemical transformations in a highly selective and efficient manner. The ability of metal complexes to perform a particular chemical reaction is dependant on the properties of the primary and secondary coordination environments. Development of transition metal complexes that catalyze the formation of organic compounds in a selective and highly efficient manner is of interest to synthetic chemists. Advancement in this area of research requires studies aimed at developing ligands that will give desirable properties upon binding to a metal ion. Using interactions present in biological systems, the ligands in this study have been developed to investigate the effects of the primary coordination sphere as well as hydrogen bonding interactions on complex formation as well as reactivity. Chapter 2 discusses the synthesis of terminal monomeric NiII-OH complexes with H41R. The hydroxo ligand is stabilized by two intramolecular hydrogen bonding interactions and the source of the hydroxo ligand was confirmed to be water. Attempts to deprotonate the NiII-OH complex to form a NiII-oxo complex were unsuccessful. Treating the NiII-OH complexes with KOtBu afforded the alkoxide substituted product. NiII-siloxide complexes were isolated upon reaction of NiII-OH with K[N(TMS)2]. Chapter 3 features the synthesis of a series of Ni(II) complexes with H2pmb, which contains two carboxyamido units appended from pyridine rings. Four Ni(II) complexes were synthesized and structurally characterized. It was determined that the carboxyamido groups either provided intramolecular H-bonds or the carbonyl oxygen can bind directly to the metal center. Chapter 4 explores the electrochemistry of the Ni(II) complexes characterized in Chapter 3. Based upon the observed reduction potentials, the reduction chemistry of [NiIIH2pmb(Cl)2] was explored. Further reactivity of the reduced species was also explored with dioxygen. Preliminary reactivity studies will also be discussed.

Download or read book Metal Dihydrogen and Bond Complexes written by Gregory J. Kubas and published by Springer Science & Business Media. This book was released on 2006-04-18 with total page 479 pages. Available in PDF, EPUB and Kindle. Book excerpt: According to R.H. Crabtree, Metal Dihydrogen and sigma-Bond Complexes is described as `the definitive account of twentieth-century work in the area of sigma complexation'. It covers not only Kubas' discovery of dihydrogen coordination and the study of its structure and general properties but also discusses both the theoretical beliefs and experimental results of bonding and activation of dihydrogen on metal centers and the coordination and activation of C-H, B-H, X-H, and X-Y bonds, giving an overview of `one of the hottest areas in chemistry'.

Download or read book Synthesis of Phosphino silyl Ligated Nickel Complexes for the Catalytic Hydroboration of Alkenes written by Sydney Shepard and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bis(phosphino)silyl (PSiP) pincer ligands have been studied extensively. While there are several examples of late transition metal complexes, in recent years there has been a shift to study these ligands on first-row transition metals (i.e., Fe, Co, Ni). These complexes have shown to be active in catalytic hydrofunctionalization; however, the turn-over for larger substrates has proved challenging. Therefore, the question of reducing the size of the phosphino(silyl) ancillary ligand is investigated in this document. While varying the substitution at phosphorus is common, access to smaller substituents is not straightforward. A different approach is to eliminate a phosphine donor. A new bidentate PSi ligand has been synthesized and studied with respect to Ni complexes. In this regard, studying the catalytic hydroboration with a substrate scope involving terminal, di-, and tri-substituted alkenes and three Ni(II) precatalysts has been explored, where selectivity for chain-walking of internal alkenes to the terminal position was observed.