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Book Kinetic Studies of Ligand substitution and Oxidation reduction Reactions of Oxalato cobalt III Complexes in Aqueous Solution

Download or read book Kinetic Studies of Ligand substitution and Oxidation reduction Reactions of Oxalato cobalt III Complexes in Aqueous Solution written by Hin-Fat Lee and published by . This book was released on 1968 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Catalysis of Redox Reactions Between Cobalt Complexes in Aqueous Solution

Download or read book Catalysis of Redox Reactions Between Cobalt Complexes in Aqueous Solution written by A. K. Penman and published by . This book was released on 1980 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Mechanisms of Inorganic and Organometallic Reactions

Download or read book Mechanisms of Inorganic and Organometallic Reactions written by M.V. Twigg and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: This series provides a continuing critical review of the literature concerned with mechanistic aspects of inorganic and organometallic reactions in solu tion, with coverage over the whole area being complete in each volume. The format of this second volume is very similar to that of the first, with material arranged according to reaction type and compound type along generally accepted lines. Papers discussed are selected on the basis of relevance to the elucidation of reaction mechanisms but may also include results of a nonkinetic nature, such as stereochemical studies and product ratios, when useful mechanistic information can be deduced. In this volume extra space has been given to areas concerned with electron transfer processes and substitution reactions of inert complexes, and to improve convenience for the reader the text has been further divided to form three additional chapters. Electron transfer processes are discussed in three chapters: "General and Theoretical," "Reactions between Two Complexes," and "Metal-Ligand Redox Reactions," while six chapters are concerned with substitution and related reactions. Here reactions of inert chromium and cobalt complexes are discussed in separate chapters. The period of literature coverage is January 1981 through June 1982 inclusive and in a few instances, where delays in delivery of journals have been encountered, the issues not covered will be included in the next volume.

Book Oxidation State Roulette

Download or read book Oxidation State Roulette written by Brandon Fitchett and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of rare and expensive noble metals in the chemical industry as organometallic catalysts has grown exponentially in the past few decades due to their high activity, selectivity and their ability to catalyze a wide range of reactions. With this growth in use has also come a proportional growth in concern as these toxic metals inevitably leach into the environment and their negative effects on public health and our ecosystems are becoming better understood. First-row transition metal catalysts provide both environmental and economic benefits as alternatives to these noble metals due to their lower toxicity and cheaper costs. The two-electron chemistry that makes the noble metals so attractive however, is more challenging to accomplish with first-row transition metals. Intelligently designing the ligand scaffold which surrounds the metal can mitigate or even eliminate some of the shortfalls of these first-row metals. Some key features that should be considered when designing a ligand are: 1) a strong chelating ability so the ligand can stay attached to the metal, 2) incorporation of strong donors to favour low-spin complexes, 3) inclusion of hemilabile groups to allow for substrate activation and metal stabilization throughout various oxidation states, 4) redox activity to be able to donate or accept electrons, and 5) inclusion of Lewis base functionalities which are able to assist the substrate activation. Ligands which incorporate these features are known as bifunctional ligands as they can accomplish more than one function in the catalytic cycle. Developing first-row transition metal complexes containing these ligands may enable these species to replicate the reactivity and selectivity generally associated with the precious metals. Being able to replace the noble metals used in industry with these catalysts would have tremendous environmental and economic benefits. The objective of this thesis is to advance the field of bifunctional catalysis by examining the behaviour of two sterically svelte, tridentate SNS ligands containing hard nitrogen and soft sulphur donors when bonded to cobalt. Previous work with iron provides a template of the ligand behaviour to which cobalt can be compared, allowing us to contrast the effects exerted by the different metals. After an introduction to bifunctional catalysis in Chapter 1, Chapter 2 describes the reactivity of the amido ligand, SMeNHSMe, with precursors ranging from Co(I) to Co(III), all of which yielded the 19e- pseudooctahedral cobalt(II) bis-amido complex, Co(SMeN-SMe)2 characterized by 1H NMR spectroscopy, single-crystal X-ray crystallography and cyclic voltammetry. Although this complex has a similar structure as the Fe analogue, the cobalt bis-amido complex did not exhibit the same hemilabile behaviour that allowed for simple ligand substitution of one of the thioether groups. Instead it reacted reversibly with 2,2'-bipyridine while 1,2-bis(dimethylphosphino)ethane (DMPE) and 2,6-dimethylphenyl isocyanide both triggered additional redox chemistry accompanied by the loss of protonated SMeNHSMe. In contrast, protonation gave the cobalt(II) amido-amine cation, [Co(SMeNSMe)(SMeNHSMe)](NTf2), which allowed for substitution of the protonated ligand by acetonitrile, triphenylphosphine and 2,2'-bipyridine based on 1H NMR evidence. The ability of Co(SMeNSMe)2 to act as a precatalyst for ammonia-borane dehydrogenation was also probed, revealing that it was unstable under these conditions. Addition of one equivalent of DMPE per cobalt, however, resulted in better activity with a preference for linear aminoborane oligomers using ammonia-borane and, surprisingly, to a change in selectivity to prefer cyclic products when moving to methylamine-borane. Chapter 3 delves into the chemistry of the thiolate ligand, SMeNHS, which formed a new 18e- cobalt(III) pseudooctahedral complex, Co(S-NC-)(SMe)(DEPE), from oxidative addition of the Caryl-SMe bond. Scaling up this reaction resulted instead in formation of an imine-coupled [Co(N2S2)]- anion which was characterized by 1H NMR/EPR spectroscopy, single-crystal X-ray diffraction, cyclic voltammetry and DFT studies. The latter revealed an interesting electronic structure with two electrons delocalized in the ligand, demonstrating the non-innocent nature of the N2S2 ligand. While the analogous iron complex proved to be an effective pre-catalyst for the hydroboration of aldehydes with selectivity against ketones, this behaviour was not observed with [Co(N2S2)]- which gave a slower rate and less selectivity. The knowledge acquired from this thesis work has advanced the field of bifunctional catalysis by extending the application of these two SNS ligands from iron to cobalt, revealing unpredictable differences in reactivity between the metals. By comparing the behaviour of these ligands with iron and cobalt, we gain a better understanding of the chemistry that is accessible by these ligands and the applications for which they may be used. This increased knowledge contributes to our long-term goal of replacing expensive and toxic noble metals with more benign first-row transition metals, improving the sustainability of the chemical industry.

Book Reactions of Some Mononuclear and Binuclear Cobalt III Complexes in Aqueous Solution

Download or read book Reactions of Some Mononuclear and Binuclear Cobalt III Complexes in Aqueous Solution written by Julian David Edwards and published by . This book was released on 1974 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Ligand Exchange Reactions of Some Cobalt III Complexes

Download or read book Ligand Exchange Reactions of Some Cobalt III Complexes written by Thomas Madison Vickrey and published by . This book was released on 1974 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Investigation of New Ligand Architechtures Towards Proton and Water Reduction Catalysis by Cobalt Complexes

Download or read book Investigation of New Ligand Architechtures Towards Proton and Water Reduction Catalysis by Cobalt Complexes written by Debashis Basu and published by . This book was released on 2015 with total page 279 pages. Available in PDF, EPUB and Kindle. Book excerpt: We designed several redox-active ligand architectures to optimize and understand the redox, electronic, and catalytic properties of their respective cobalt complexes. Ligand design was varied from pentadentate donor phenolate to tetradentate acceptor oxime in order to reduce the overpotential of hydrogen generation in organic solvents. We altered the substitution, axial ligands and axial ligand substitutions to vary electronic and catalytic properties for such tetra- or pentadentate ligand systems. Knowledge of the nature of the active species for catalysis enabled us to design the pentadentate oxime ligand which exhibited rich reaction chemistry along with suitable catalytic property in organic solvent. Presence of several polar groups like -OH and -NH and the absence of any aromatic rings make this complex water soluble which is an added advantage. Additionally, this complex exhibited excellent catalytic properties in water with low onset overpotential and high turnover number. We developed similar redox-active-acceptor pentadentate phenylene-bridged pyridine-rich ligand which provided extremely versatile reaction chemistry after complexation with cobalt. These complexes displayed catalytic properties at moderate to low-overpotential in acetonitrile with good turnover numbers. Furthermore, the water solubility and tunability of such complexes make them suitable candidates for water reduction. Therefore, water reduction was carried out with these complexes showing low onset overpotentials and high turnover numbers. Finally, we incorporated [Ru(bpy)2]2+-based photosensitized with one of the catalytic module (cobalt tetradentate oxime) to generate heterobimetallic [RuIICoIII] species which displayed quenching of CoIII upon electron transfer from RuII excited state.

Book Reaction Mechanisms of Metal Complexes

Download or read book Reaction Mechanisms of Metal Complexes written by R W Hay and published by Elsevier. This book was released on 2000-03-01 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text provides a general background as a course module in the area of inorganic reaction mechanisms, suitable for advanced undergraduate and postgraduate study and/or research. The topic has important research applications in the metallurgical industry and is of interest in the science of biochemistry, biology, organic, inorganic and bioinorganic chemistry. In addition to coverage of substitution reactions in four-, five- and six-coordinate complexes, the book contains further chapters devoted to isomerization and racemization reactions, to the general field of redox reactions, and to the reactions of coordinated ligands. It is relevant in other fields such as organic, bioinorganic and biological chemistry, providing a bridge to organic reaction mechanisms. The book also contains a chapter on the kinetic background to the subject with many illustrative examples which should prove useful to those beginning research. Provides a general background as a course module in the area of inorganic reaction mechanisms, which has important research applications in the metallurgical industry Contains further chapters devoted to isomerization and racemization reactions, to the general field of redox reactions, and to the reactions of coordinated ligands

Book Iron and Cobalt Catalysts

Download or read book Iron and Cobalt Catalysts written by Wilson D. Shafer and published by MDPI. This book was released on 2020-06-23 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the turn of the last century when the field of catalysis was born, iron and cobalt have been key players in numerous catalysis processes. These metals, due to their ability to activate CO and CH, haev a major economic impact worldwide. Several industrial processes and synthetic routes use these metals: biomass-to-liquids (BTL), coal-to-liquids (CTL), natural gas-to-liquids (GTL), water-gas-shift, alcohol synthesis, alcohol steam reforming, polymerization processes, cross-coupling reactions, and photocatalyst activated reactions. A vast number of materials are produced from these processes, including oil, lubricants, waxes, diesel and jet fuels, hydrogen (e.g., fuel cell applications), gasoline, rubbers, plastics, alcohols, pharmaceuticals, agrochemicals, feed-stock chemicals, and other alternative materials. However, given the true complexities of the variables involved in these processes, many key mechanistic issues are still not fully defined or understood. This Special Issue of Catalysis will be a collaborative effort to combine current catalysis research on these metals from experimental and theoretical perspectives on both heterogeneous and homogeneous catalysts. We welcome contributions from the catalysis community on catalyst characterization, kinetics, reaction mechanism, reactor development, theoretical modeling, and surface science.

Book Electron Transfer Reactions of Complex Ions in Solution

Download or read book Electron Transfer Reactions of Complex Ions in Solution written by Henry Taube and published by Elsevier. This book was released on 2012-12-02 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electron Transfer Reactions of Complex Ions in Solution covers the significant development of some important area of electron transfer reactions of complex ions. This four-chapter book emerged from a series of lectures at the Polytechnic Institute of Brooklyn in November and December 1967. Chapter I presents research studies in cation hydration. This chapter describes principal methods for composition determination of the first coordination spheres of the aquo ions. Chapter II examines the distinction between reactions in which electron transfer takes place from one primary bond system to another. Chapter III discusses some aspects of ligand effects in electron-transfer reactions. This chapter demonstrates that differences in the behavior of systems can be expected at least in the extremes of mechanisms. Chapter IV deals with the history, principles and applications of the induced electron-transfer effect. This book is of great value to electrochemists, students, and researchers.

Book Ligand Substitution and Cyclic Photoassisted Oxidation reduction Reactions Employing a Macrocyclic Iron Complex

Download or read book Ligand Substitution and Cyclic Photoassisted Oxidation reduction Reactions Employing a Macrocyclic Iron Complex written by David William Reichgott and published by . This book was released on 1976 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Chemistry Electrochemistry and Electron Transfer Induced Reactions of Cobalt Complexes with Fluorinated Ligands

Download or read book Chemistry Electrochemistry and Electron Transfer Induced Reactions of Cobalt Complexes with Fluorinated Ligands written by Kihanduwage N. Gunawardhana and published by . This book was released on 2007 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: The chemical or electrochemical reduction of the trifluoroacetyl complex CF3COCo(CO)3PPh3 involves a single electron transfer yielding trifluoromethyl radical and an anionic cobalt carbonyl complex. The mechanism is proposed to involve electron transfer followed by initial dissociation of either a carbonyl or phosphine ligand from the 19-electron [CF3COCo(CO)3PPh3]- anion. The resulting 17-electron intermediate undergoes subsequent one-electron reductive elimination of trifluoromethyl radical by homolytic cleavage of the carbon-carbon bond of the trifluoroacetyl group. The CF3. radical can be trapped by either benzophenone anion, forming the anion of [alpha]-(trifluoromethyl)benzhydrol, or Bu3SnH, yielding CF3H. The final organometallic product is an 18-electron anion, either [Co(CO)4]- or [Co(CO)3(PPh3)]-, depending upon which ligand is initially lost. The chemical or electrochemical reduction CF3Co(CO)3PPh3 is a two-electron process involving heterolytic cobalt-carbon bond cleavage to yield trifluoromethyl anion and cobalt carbonyl anions. The trifluoromethyl anion rapidly decomposes to fluoride and difluorocarbene. This carbene may dimerize to form C2F4. The unstable fluoro carbene can also be trapped by cyclohexene. The mechanism proposed for the reduction of C6F5Co(CO)3PPh3 involves a homolytic cobalt-carbon bond cleavage to form C6F5. radical. The resultant C6F5. radical abstracts hydrogen or deuterium from the solvent or trace amounts of water to produce C6F5H or C6F5D. With an excess of reducing agent this C6F5. radical can be further reduced to C6F5- anion before forming pentafluorobenzene by protonation. The inorganic fragment, the 18-electron [Co(CO)3PPh3]- anion, may participate in a ligand exchange reaction to form [Co(CO)4]-. In addition, interesting reactivity was observed between C6F5Co(CO)3PPh3 and tin hydrides, deuterides and chlorides without any reducing agents. We have demonstrated that ligand replacement reactions can be used for the synthesis of new cobalt-NHC complexes with fluorinated alkyl, acyl and aryl ligands. In addition, the X-ray crystal structure of CF3COCo(CO)3PPh3 was obtained to compare the bond lengths and bond angles with other related compounds. An unusual Co-C(acyl) bond length was observed for CF3COCo(CO)3PPh3. Considering the bond lengths of other alkyl and acyl complexes, it can generally be argued that the position of the alkyl/acyl equilibrium varies with the Co-C(alkyl/acyl) bond length.

Book Substitution Reactions of Some Cobalt Complexes in High Dielectric Constant Solvent

Download or read book Substitution Reactions of Some Cobalt Complexes in High Dielectric Constant Solvent written by Emily Virginia Timm and published by . This book was released on 1967 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: