Download or read book Investigations of Homogeneous Ruthenium and Cobalt Complexes for Electrocatalytic Transformations written by Kate M. Waldie and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition metal hydrides are key intermediates implicated in a wide range of chemical and electrochemical transformations. Herein, select examples of molecular transition metal hydride complexes and their applications in critical hydrogen transfer reactions, specifically transfer hydrogenation, electrocatalytic alcohol oxidation, and electrocatalytic hydrogen evolution, are presented. An octahedral Ru-hydride complex reacts rapidly and irreversibly with CO2 under ambient conditions to yield the Ru-formate. The analogous insertion of various ketones yields an equilibrium mixture of the hydride and alkoxide complexes, for which the equilibrium constants are measured by 1H NMR. Density functional theory is used to compare the mechanism of acetone and CO2 insertion. Investigations on the kinetic profile of transfer hydrogenation with the Ru-hydride complex reveal some key aspects of the mechanism. The Ru-hydride undergoes an irreversible oxidation at low potential by cyclic voltammetry. In the presence of alcohol and alkoxide base, large current enhancement is observed at this potential, consistent with electrocatalytic alcohol oxidation. The synthesis and characterization of a family of dicationic Co(III) complexes with bidentate nitrogen ligands are presented. Upon addition of protonated N, N-dimethylformamide buffer, electrocatalytic hydrogen evolution is observed at onset potentials near -1.1 V. Further studies demonstrate that these complexes decompose under acidic reducing conditions to form an active species at the electrode surface. A Co(III)-azopyridine complex exhibits a reversible 2e- reduction at very mild potentials. Chemical reduction with cobaltocene yields a neutral complex as an air stable, diamagnetic solid. Spectroscopic and crystallographic studies illuminate key structural and electronic changes that occur upon reduction, indicating that the neutral complex is best described as a highly delocalized system. Protonation of the neutral species yields a monocationic hydrazino complex. All three cleavage modes (i.e. proton, hydride, and hydrogen atom) for this ligand N-H bond are demonstrated. Studies on the stoichiometric reactivity of this complex with the triphenylcarbenium cation and TEMPO radical are explored.
Download or read book The Development and Investigation of Cobalt Catalysts for the Chemical Transformations Related to Artificial Photosynthesis written by Hyun Seo Ahn and published by . This book was released on 2013 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chapter 1. Small domains of cobalt on silica (CoSBA) were prepared by the reaction of Co[N(SiMe3)2]2 and SBA-15, resulting in a range of surface structures as the cobalt loading varied from 0.27 to 5.11 wt%. X-ray absorption spectroscopy (XAS) was employed to characterize these surface structures, which range from single-site cobalt atoms to small clusters of Co3O4. The CoSBA materials exhibit photochemical water oxidation catalysis, revealing distinct catalytic activities associated with characteristic types of surface structures that are dominant in particular concentration regimes. The catalytic turnover frequency for water oxidation of an isolated single-site cobalt atom (0.0143 s−1) is much greater than that observed for a surface atom of a small cluster Co3O4 on silica (0.0006 s−1). The CoSBA catalysts were recyclable for more than seven catalytic cycles (> 200 turnovers) with additional sacrificial oxidant, and no leaching of cobalt was observed. Post-catalytic analysis of CoSBA by XAS revealed that the cobalt atoms were partially oxidized to Co3+, without exhibiting significant surface migration and aggregation of cobalt atoms. Chapter 2. Single-site cobalt atoms on various oxide surfaces (TiO2, MgO, SBA-15, AlPO, and Y-Zeolite) were prepared and evaluated as water oxidation catalysts. Superior catalytic rates were observed for cobalt sites on basic supporting oxides (TiO2 and MgO) relative to those on acidic oxides (Y-Zeolite, AlPo, and SiO2). Per-atom turnover frequencies of ca. 0.04 s−1 were achieved, giving initial rates 100 times greater than a surface atom of a Co3O4 nanoparticle. No correlation was observed between catalytic rates and oxygen atom affinities of the supporting oxides. Chapter 3. Cobalt metaphosphate Co(PO3)2 nanoparticles are prepared via the thermolytic molecular precursor (TMP) method. A Ni foam electrode decorated with Co(PO3)2 nanoparticles is evaluated as an anode for water oxidation electrocatalysis in pH 6.4 phosphate-buffered water. Catalytic onset occurs at an overpotential of ca. 310 mV, which is 100 mV lower than that observed for Co3O4 nanoparticles, with a comparable surface area under identical conditions. A per-metal turnover frequency (TOF) of 0.10 - 0.21 s−1 is observed at [eta] = 440 mV, which is comparable to the highest rate reported for a first-row metal heterogeneous catalyst. Post-catalytic characterization of the catalyst resting state by XPS and Raman spectroscopy reveals that surface rearrangement occurs, resulting in an oxide-like surface overlayer. Chapter 4. Linear trimetallic CoIII/CoII/CoIII cobalt complexes with bridging acyl-alkoxy ligands are electrocatalysts for the reduction of tosic acid in acetonitrile. The -OCMe2CH2COMe complex appears to operate homogeneously, and at an onset overpotential of only 25 mV. A turnover frequency of ca. 80 s−1 was observed at an overptotential of 150 mV.
Download or read book Studies on Mixed metal Clusters Containing Cobalt Ruthenium and Rhodium and on the Catalytic Reactivity of Homogeneous Ruthenium rhodium and Ruthenium cobalt Systems written by Jouni Pursiainen and published by . This book was released on 1986 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Chemical and Electrochemical Investigations of Cobalt Cyanide and Ruthenium Ammine Complexes written by Hong Sup Lim and published by . This book was released on 1972 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Homogeneous Catalysis Concepts and Basics written by Mohammad Reza Rahimpour and published by Elsevier. This book was released on 2024-08-30 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: Homogeneous Hydrogenation and Metathesis Reactions, a volume in the Advances in Catalysis series, covers hydrogenation and metathesis reactions in two separate sections. The first section is devoted to homogeneous hydrogenation reactions and related processes, including hydrogenation of alkenes, esters, olefins, etc. In the second section, the metathesis reactions of olefins, alkenes, and alkynes are presented. In addition, the industrial application of homogeneous metathesis reactions is investigated. Includes thermodynamic and kinetic studies of homogeneous catalysts Describes transition metal, ligand and solvent role in homogeneous catalysts Explains preparation, characterization, deactivation and regeneration of homogeneous catalysts Presents homogeneous catalysts by clusters, carbenes, fixed metal-complexes, and liquid-liquid multiphase catalysts
Download or read book Development of Cationic Cobalt I complexes for Enantioselective Cycloaddition and Hydrofunctionalization Reactions written by Mahesh M. Parsutkar and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Developments of new catalytic transformations by using earth-abundant metal (base-metal) catalysts have played a significant role in modern civilization and will continue to play a vital role towards maintaining and improving our quality of life. Particularly, these transformations have had a tremendous impacts on the agricultural, transport, energy, and pharmaceutical sectors. This field of base-metal catalysis would enjoy added benefits with the utilization of sustainable feedstock carbon sources for fine chemical synthesis. However, the dual problems of activation of thermodynamically stable precursors (ethylene, CO2, H2, CO, aldehydes, acrylates, HCN) and their highly stereoselective incorporation into other readily available substrates (1,3-dienes, alkynes, enynes) pose new challenges. In a nutshell, the development of benign catalysts for employing sustainable feedstock starting materials has the potential to transform inexpensive materials into valuable precursors for fine chemical synthesis. My dissertation work focuses on the development of scalable, atom-economical, and cost-effective catalytic methods for the preparation of value-added products relevant to fine chemicals. The overarching aims are to use sustainable feedstocks or readily available precursors, and environmentally benign chemistry. To achieve these goals, three efficient catalytic methods have been developed which employ complexes of an earth-abundant metal, cobalt, with ligands derived from naturally occurring amino acids or commercially available bis-phosphine ligands. The key to success was a systematic ligands investigation that inspired the design and synthesis of novel ligands to achieve high chemo-, regio-, and enantioselectivities. In the first methodology, a broadly applicable method affecting [2+2] cycloaddition between several alkynes and alkenyl derivatives to form cyclobutenes has been disclosed. A library of >70 nearly enantiopure cyclobutenes, which are ubiquitous motifs in bioactive compounds, have been synthesized in excellent yields. In the second methodology, ligand controlled regio-divergent enantioselective synthesis of primary and secondary homoallylic boronates (>50 examples) from readily available 1,3-dienes and a common boron reagent have been developed. Furthermore, the hydrofunctionalization of 1,3-dienes program has been extended to unprecedented enantioselective hydroacylation of 1,3-dienes. This method opens a realm to achieve the synthesis of enantiopure alpha- or beta-chiral center containing ketones. In all the mentioned transformations above, cationic Co(I)- species has been invoked as an active catalyst. To further corroborate the role of cationic Co(I)-complexes, a reliable protocol has been developed to synthesize, isolate discrete neutral and cationic Co(I)-complexes and characterized by X-ray crystallography. These isolated cationic complexes serve as an excellent single-component catalyst for heterodimerization, hydroboration, and hydroacylation, suggesting the key role of cationic Co(I)-complexes in these transformations. While developing these efficient methodologies, striking ligand, counterion, and solvent effects have been revealed along with a unique role of a cationic Co(I) intermediate in the reactions which advanced novel fundamental concepts. We believe that these cationic Co(I) complexes have broader utility in homogeneous catalysis. We hope that the rational evolution of a mechanism-based strategy that led to the eventual successful outcome and the attendant support studies will add to the burgeoning organometallic chemistry of cobalt and its applications with further implications beyond the synthetic reactions described in this dissertation.
Download or read book Clathrochelates written by Y.Z. Voloshin and published by Elsevier. This book was released on 2002-09-19 with total page 433 pages. Available in PDF, EPUB and Kindle. Book excerpt: Clathrochelates are compounds which contain a metal ion encapsulated within a three dimensional cage of macrobicyclic ligand atoms. Within this cage the metal has unique properties and is to a great extent isolated from environmental factors. Such complexes are suitable as models of the most essential biological systems, membrane transport, electron carriers, highly selective and sensitive analytical reagents, catalysts for photochemical and redox processes, cation and anion receptors, etc. The aim of this monograph is to generalize and analyze experimental and theoretical data on clathrochelates in order to promote further research in this promising field of chemistry. Chapter 1 gives general concepts of complexes with encapsulated metal ions, discusses basic specific features of these compounds, considers and characterizes the main types of compounds with encapsulated metal ions and the main classes of clathrochelates, and includes the current nomenclature. Chapter 2 deals with the pathways of clathrochelate synthesis and the general procedures for the synthesis of macrobicyclic tris-dioximates, phosphorus-containing tris-diiminates, sepulchrates, sarcophagi-nates, and polyene and other types of clathrochelate complexes. Chapter 3 concerns studies of the electronic and spatial structure of clathrochelate complexes. In Chapter 4, the kinetics and mechanism of synthesis and decomposition reactions of macrobicyclic tris-dioximates, sarcophaginates, and sepulchrates in solution and gas phases are discussed. Chapter 5 considers the electrochemical, photochemical, and some other characteristics of clathrochelates and their applications associated with these characteristics. Finally, the practical applications of the unique properties of clathrochelates and perspectives on the synthesis of new clathrochelates are described in Chapters 6 and 7, respectively.
Download or read book Transformation of Carbon Dioxide to Formic Acid and Methanol written by Wan-Hui Wang and published by Springer. This book was released on 2017-10-26 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: This brief explains the principles and fundamentals of carbon dioxide utilization and highlights the transformation to fuels and value-added chemicals such as formic acid and methanol. It is divided into six chapters, including an introduction to the basics of CO2 utilization and transformation of CO2 to formic acid and methanol with homogeneous and heterogeneous catalysts, respectively. The brief will appeal to a wide readership of academic and industrial researchers focusing on homogeneous and heterogeneous catalysis, organometallic chemistry, green chemistry, energy conversion and storage.
Download or read book Surface Attached Ruthenium Complexes for Oxidative Electrochemistry and Development of Dimeric Cobalt Oxygen Evolution Electrocatalysts written by and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The oxygen evolution reaction (OER) is the anodic half reaction required to convert water into storable chemical fuels and remains a key bottleneck in sustainable energy production. Numerous synthetic molecular complexes, primarily Ru polypyridyls, have been reported that perform OER catalysis. This thesis work is divided into two main areas of focus: the development of methods for attaching alkyne-modified Ru complexes to electrode surfaces via Cu-catalyzed azide-alkyne cycloaddition (CuAAC) "click" chemistry to generate functionalized electrodes, and the development of a new class of molecular OER catalysts based on earth abundant Co. Efforts to attach Ru complexes to electrode surfaces initially targeted an alkyne-modified derivative of a previously reported Ru polypyridyl OER catalyst. The modified complex was successfully prepared and attached to azide-functionalized graphite electrodes, though the graphite electrodes proved insufficient to withstand the strongly oxidizing conditions required for OER catalysis. Attempts to attach the catalysts to functionalized conductive diamond electrodes proved successful and redox chemistry was observable on the time scale of cyclic voltammetry, however the attachment proved unstable to electrolysis at potentials relevant to OER catalysis. In order to demonstrate the fundamental stability of the functionalized diamond electrodes separate from catalysis an alkyne-modified Ru(tpy)2 derivative was prepared and tethered to conductive diamond. This functionalized diamond electrode showed good stability in aqueous solvents and excellent stability in non-aqueous solvents for >500,000 cycles. In a separate project, structural analogies between known Ru OER catalysts and CoIII bridging-peroxo dimers inspired the evaluation of such Co complexes as OER catalyst candidates. When the known compounds studied were shown to be unstable in aqueous media, a new series of peroxo dimers supported by a bridging bispyridylpyrazolate (bpp) ligand were prepared. These complexes display excellent stability in water and aqueous electrochemistry supports their ability to serve as electrocatalysts for OER. Oxidized intermediate species have been identified and characterized suggesting an OER mechanism that resembles mechanisms proposed for CoOx heterogeneous OER catalysts. In addition to OER activity the bpp-Co peroxo complexes are shown to perform the oxygen reduction reaction, making these complexes among the few examples of molecular complexes capable of performing both catalytic processes.
Download or read book Elements of Molecular and Biomolecular Electrochemistry written by Jean-Michel Savéant and published by John Wiley & Sons. This book was released on 2006-02-10 with total page 505 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is based on the George Fisher Baker Lecture given by Jean-Michel Savéant at Cornell University in Fall 2002. * The first book focusing on molecular electrochemistry * Relates to other fields, including photochemistry and biochemistry * Outlines clearly the connection between concepts, experimental illustrations, proofs and supporting methods * Appendixes to provide rigorous demonstrations to prevent an overload of algebra in the main text * Applications-oriented, focused on analyzing the results obtained rather than the methodology
Download or read book Homogeneous Photocatalysis written by M. Chanon and published by John Wiley & Sons. This book was released on 1997-03-06 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photocatalysis and related processes occupy a strategic position for the future of photochemistry. This volume provides an introduction to basic concepts and explains how applications work at the molecular level.
Download or read book Functional Metallosupramolecular Materials written by John Hardy and published by Royal Society of Chemistry. This book was released on 2015-07-17 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is great interest in metallosupramolecular materials because of their use in magnetic, photonic and electronic materials. Functional Metallosupramolecular Materials focuses on the applications of these materials covering the chemistry underlying the synthesis of a variety of ligands to coordinate various metal ions and the generation of 2D and 3D materials based on these constructs. The book starts by looking at different metallosupramolecular systems including naturally occurring functional metallosupramolecular materials; DNA-based metallosupramolecular materials; metallopolymers; metallogels as well as functional materials based on MOFs. Subsequent chapters then systematically cover the different applications such as molecular computation, spin-crossover, light harvesting and as photocatalysts for the production of solar fuels. The book provides an overview of functional metallosupramolecular materials that will be of interest to graduate students, academics and industrial chemists interested in supramolecular chemistry, materials science and the materials applications. Priced at £159.00, US$260.00, €198.75
Download or read book New and Future Developments in Catalysis written by Steven L Suib and published by Newnes. This book was released on 2013-07-19 with total page 493 pages. Available in PDF, EPUB and Kindle. Book excerpt: New and Future Developments in Catalysis is a package of seven books that compile the latest ideas concerning alternate and renewable energy sources and the role that catalysis plays in converting new renewable feedstock into biofuels and biochemicals. Both homogeneous and heterogeneous catalysts and catalytic processes will be discussed in a unified and comprehensive approach. There will be extensive cross-referencing within all volumes.The use of solar energy during various catalytic chemical processes for the production of an array of chemical products is the theme of this volume. Photocatalysis is a topic of increasing importance due to its essential role in many of today’s environmental and energy source problems. The use of solar energy for catalytic reactions results in a carbon dioxide–neutral process. All photocatalytic processes and the future developments in this area are discussed, including an economic analysis of the various processes. Offers in-depth coverage of all catalytic topics of current interest and outlines future challenges and research areas A clear and visual description of all parameters and conditions, enabling the reader to draw conclusions for a particular case Outlines the catalytic processes applicable to energy generation and design of green processes
Download or read book Acid base Dissociation Constants in Dipolar Aprotic Solvents written by Kōsuke Izutsu and published by Blackwell Science Incorporated. This book was released on 1990-01-01 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cage Metal Complexes written by Yan Voloshin and published by Springer. This book was released on 2017-05-11 with total page 475 pages. Available in PDF, EPUB and Kindle. Book excerpt: This fundamental book presents the most comprehensive summary of the current state in chemistry of cage metal complexes. After their previous book “The Encapsulation Phenomenon” (www.springer.com/978-3-319-27737-0) the authors in this book focus on the encapsulation of metal ions by different types of three-dimensional mono- and polynucleating caging ligands. Within these cage metal complexes, (metal) ions can be isolated from external factors. The book provides both a classification of the cage compounds and summaries of synthetic approaches. On that basis the authors then describe the unique chemical and physical properties and the resulting reactivity of the cage compounds, as well as practical and potential applications as potent topological drugs and prodrugs, antifibrillogenic agents, radiodiagnostic and radiotherapeutic compounds, paramagnetic probes, single-molecule magnets, electrocatalysts for hydrogen production, (photo)electronic devices, and many more. Readers will find a well-structured and concise overview, with particular emphasis on a review of synthesis and reactivity of various cage metal complexes, summarizing over 400 literature references, clearly presented in over 300 color schemes and figures.
Download or read book Homogeneous Hydrogenation written by P.A. Chaloner and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt: Homogeneous hydrogenation is one of the most thoroughly studied fields of homogeneous catalysis. The results of these studies have proved to be most important for an understanding of the underlying principles of the activation of small molecules by transition metal complexes. During the past three decades homogeneous hydrogenation has found widespread application in organic chemistry, including the production of important pharmaceuticals, especially where a sophisticated degree of selectivity is required. This volume presents a general account of the main principles and applications of homogeneous hydrogenation by transition metal complexes. Special attention is devoted to the mechanisms by which these processes occur, and the role of the recently discovered complexes of molecular hydrogen is described. Sources of hydrogen, other than H2, are also considered (transfer hydrogenation). The latest achievements in highly stereoselective hydrogenations have made possible many new applications in organic synthesis. These applications are documented by giving details of the reduction of important unsaturated substrates (alkenes, alkynes, aldehydes and ketones, nitrocompounds, etc.). Hydrogenation in biphasic and phase transfer catalyzed systems is also described. Finally, a discussion of the biochemical routes of H2 activation highlights the similarities and differences in performing hydrogenation in both natural and synthetic systems. For researchers working in the fields of homogeneous catalysis, especially in areas such as pharmaceuticals, plastics and fine chemicals.
Download or read book Comprehensive Treatise of Electrochemistry written by John Bockris and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is now time for a comprehensive treatise to look at the whole field of electrochemistry. The present treatise was conceived in 1974, and the earliest invitations to authors for contributions were made in 1975. The completion of the early volumes has been delayed by various factors. There has been no attempt to make each article emphasize the most recent situation at the expense of an overall statement of the modern view. This treatise is not a collection of articles from Recent Advances in Electrochemistry or Modern Aspects of Electrochemistry. It is an attempt at making a mature statement about the present position in the vast area of what is best looked at as a new interdisciplinary field. Texas A & M University J. O'M. Bockris University of Ottawa B. E. Conway Case Western Reserve University Ernest Yeager & M University Texas A Ralph E. White Preface to Volume 2 This volume brings together some dozen processes well known to the electro chemist and treats them according to their various degrees of importance. The production of hydrogen is one of the more important processes, particularly with respect to the prospects of a hydrogen economy. No one would doubt, however, that the most commercially important electrochemical processes at the present time are the production of aluminum and of chlorine. Each of these processes has a separate chapter devoted to it.
