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Mono- and binuclear cobalt hydridesNg, Jesse B. January 1990 (has links)
The homogeneous hydrogenation of arenes with functional groups was studied with allylcobalt complexes containing the bulky chelating diphosphines dippp (1,3-bis(diisopropylphosphino)propane and dippcyp (trans-(±)-l,2-bis(diisopropylphos-phino)cyclopentane). The results indicated that these catalyst precursors were unsuitable for the hydrogenation reactions, being too sensitive to the nature of the substrate. From these hydrogenation reactions, the intermediates (η⁵-cyclohexadienyl)Co(dippcyp) (10) and (η⁴-2-methoxynaphthalene)Co(H)(dippcyp) (11) were isolated and structurally characterized, thus providing some insight into the mechanism of the hydrogenation reaction.
The production of binuclear hydrides such as [(dippp)CoH₂]₂ (4) and [(dippcyp)CoH₂]₂ (9) was observed to lead to the end of the catalysis. An X-ray structural characterization of the blue hydride [(dippp)CoH₂]₂ (4) showed that in the solid state it is binuclear. Although the complex is diamagnetic in the solid state (6-280 K), in solution its paramagnetic behaviour could only be attributed to an equilibrium with a second species proposed to be mononuclear, (dippp)CoH₂. In addition, a cyclic voltammogram of the complex in solution indicated that the predominant species still was the binuclear compound [(dippp)CoH₂]₂ (4).
One of the syntheses of [(dippp)CoH₂]₂ (4) gave a product identified as (dippp)CoH₃ (5). Based on variable-temperature spin-lattice relaxation time (T₁) measurements and an electrochemical study, this red hydride complex appeared to contain an η²-H₂ ligand. The relationship of this complex with the blue hydride apparently involves the mononuclear species, (dippp)CoH₂. Independent pathways led to the formation of both the blue and red hydrides, and these pathways are discussed in terms of possible mechanisms. / Science, Faculty of / Chemistry, Department of / Graduate
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Structural and Physical Studies of Co(III) Salen Derivatives.Govender, Santham. January 2007 (has links)
A number of ligands that belong to the salen-type family were synthesized in this thesis.
These ligands were synthesized from salicylaldehyde and 1,2-phenylenediamine, 1,3-
diamino-2-hydroxypropane, 1,2-diamino-ethane, N-(3-aminopropyl)-1,3-propanediamine,
diethylenetriamine, diaminomaleonitrile, 2,2-dimethyl-1,3-propanediamine and 1,3-
diaminopropane. From this range of ligands, H2salophen was chosen as the ligand for further
studies.
This work is aimed primarily at elucidating the structures and spectroscopic properties of
[Co(salophen)(amine)2](OAc) derivatives, where salophen is N,N’-disalicylidene-1,2-
phenylenediamine and the amines used were butylamine, benzylamine, a-
methylbenzylamine, dibutylamine, N-methylpiperazine and piperidine. Three novel crystal
structures of [CoIII(salophen)L2]Cl derivatives, where L = butylamine, benzylamine, and
piperidine, with Co-N distances that range from 1.901 Å to 2.024 Å, have been reported in
this thesis. The novel crystal structure of [Co(salophen)(N-MePipz)(OAc)] is also reported in
this thesis. These cobalt complexes have been analysed by 1H, 13C and 59Co NMR as well as
electronic and IR spectroscopy. A 59Co NMR spectrum was obtained for the
[Co(salophen)(BuNH2)2]CH2Cl2×Cl complex. The spectrum exhibits a single line at 8504
ppm.
The binding constants of all [Co(salophen)(amine)2](OAc) complexes, where amine =
butylamine, benzylamine, a-methylbenzylamine, dibutylamine, N-methylpiperazine and
piperidine, were determined by spectroscopic titrations. The titrations were carried out at
various concentrations of the amine and at temperatures ranging from 25°C to 45°C. It was
found that the primary amines had much larger values of K1 and K2 compared to the
secondary amines. Typical values of K1 and K2 were 8000 M-1 and 63.6 M-1 respectively at
25°C, for a-methylbenzylamine. Of the primary amines, it was found that a-
methylbenzylamine had the largest value of K1 and K2 compared to the other two amines.
For the secondary amines, it was found that N-methylpiperazine had the bigger value of K1
compared to that of dibutylamine. / Thesis (M.Sc. )-University of KwaZulu-Natal, Pietermaritzburg, 2007.
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Part I, base-promoted aryl-bromine bond cleavage by cobalt(ii) porphyrins. / Base-promoted aryl-bromine bond cleavage by cobalt(ii) porphyrins / Part II, catalytic hydrodehalogenation of aryl bromides by cobalt(ii) porphyrin in alkaline conditions / Catalytic hydrodehalogenation of aryl bromides by cobalt(ii) porphyrin in alkaline conditionsJanuary 2013 (has links)
本論文主要研究了鹼性添加劑促進二價鈷卟啉絡合物(Co{U+1D35}{U+1D35}(por))在苯溶劑中與溴代苯及其衍生物(ArX)的反應及鹼性條件下,該絡合物催化溴代苯及其衍生物的脫鹵反應。 / 第一部分主要介紹了在KOH和{U+1D57}BuOH存在下,Co{U+1D35}{U+1D35}(por)斷裂碳-溴鍵(Ar-Br)形成各種三價鈷卟啉芳基絡合物(Co{U+1D35}{U+1D35}{U+1D35}(por)Ar)(eq. 1)。 / 機理研究顯示,Co{U+1D35}{U+1D35}(por)首先從ArBr中得到Br·形成芳基自由基(Ar·)及Co{U+1D35}{U+1D35}{U+1D35}(por)Br (Scheme 1, i). Ar 與另一個Co{U+1D35}{U+1D35}(por)反應得到Co{U+1D35}{U+1D35}{U+1D35}(por)Ar (Scheme 1, ii)。在鹼性條件中,Co{U+1D35}{U+1D35}{U+1D35}(por)Br 最終形成CoII(por)從而繼續反應 (Scheme 1, iii-iv)。 / 第二部份主要介紹了在200 ºC時, 鹼性條件下Co{U+1D35}{U+1D35}(por)催化鹵代苯及其衍生物脫鹵形成對應芳烴的反應 (eq. 2)。 該反應在四氫呋喃(THF)及異丙醇 ({U+2071}PrOH) 中都可以進行。 / 機理研究顯示, Co{U+1D35}{U+1D35}(ttp) 首先與ArBr反應得到Ar· 和Co{U+1D35}{U+1D35}{U+1D35}(ttp)Br (Scheme 2, i)。 Ar 從溶劑(THF 或者 {U+2071}PrOH)得到一個氫原子從而形成芳烴 (ArH) (Scheme 2, ii)。 Ar 也可以與另一個Co{U+1D35}{U+1D35}(ttp) 反應得到Co{U+1D35}{U+1D35}{U+1D35}(ttp)Ar。 在鹼性條件下, Co{U+1D35}{U+1D35}{U+1D35}(ttp)Ar水解形成ArH 和 Co{U+1D35}{U+1D35}{U+1D35}(ttp)OH (Scheme 2, iii)。 Co{U+1D35}{U+1D35}{U+1D35}(ttp)Br 與KOH進行取代反應得到Co{U+1D35}{U+1D35}{U+1D35}(ttp)OH, 并最終形成催化劑Co{U+1D35}{U+1D35}(ttp) (Scheme 1, iii-iv)。所以, 溶劑 (THF 或者 {U+2071}PrOH)及H₂O 都可以作為Co{U+1D35}{U+1D35}(ttp) 催化鹵代苯脫鹵形成芳烴的氫的來源。 / This thesis focuses on (1) the base-promoted aryl bromine bond (Ar-Br) cleavages by cobalt(II) porphyrins and (2) catalytic hydrodehalogenation of aryl bromides by cobalt(II) porphyrin in alkaline conditions. / Part I describes the aryl bromine bond cleavage with cobalt(II) porphyrin (Co{U+1D35}{U+1D35}(por)) in the presence of KOH and {U+1D57}BuOH in benzene at 150ºC to give cobalt(III) porphyrin aryls (Co{U+1D35}{U+1D35}{U+1D35}(por)Ar) (eq. 1). / [With images] / Mechanistic studies suggest that CoII(por) first abstracts the bromine atom from the aryl bromide to form aryl radical (Ar) and Co{U+1D35}{U+1D35}{U+1D35}(por)Br (Scheme 1, i). Ar· further reacts with Co{U+1D35}{U+1D35}(por) to generate Co{U+1D35}{U+1D35}{U+1D35}(por)Ar (Scheme 1, ii). Co{U+1D35}{U+1D35}{U+1D35}(por)Br undergoes ligand substitution with KOH to form Co{U+1D35}{U+1D35}{U+1D35}(por)OH, which quickly gives Co{U+1D35}{U+1D35}(por) and H₂O₂ (Scheme 1, iii). H₂O₂ undergoes base-promoted decomposition to form H₂O and O₂ (Scheme 1, iv). / [With images] / Scheme 1 Reaction Mechanism of Base-promoted Ar-Br Cleavage with Co{U+1D35}{U+1D35}(por) / Part II describes the catalytic hydrodehalogenation of aryl bromides by Co{U+1D35}{U+1D35}(ttp) at 200 ºC in alkaline conditions to generate arenes (eq. 2). The reaction can occur in both THF and {U+2071}PrOH. / [With images] / Mechanistic studies suggest that Co{U+1D35}{U+1D35}(ttp) also first abstracts the bromine atom from the aryl bromide in the presence of KOH to form Ar· and Co{U+1D35}{U+1D35}{U+1D35}(ttp)Br (Scheme 2, i). Ar· can abstract a hydrogen atom from the solvent (THF or {U+2071}PrOH) to form arenes (Scheme 2, ii). Ar also could be trapped by Co{U+1D35}{U+1D35}(ttp) to give Co{U+1D35}{U+1D35}{U+1D35}(ttp)Ar, which undergoes hydrolysis in the presence of OH⁻ to the arene (ArH) and Co{U+1D35}{U+1D35}{U+1D35}(ttp)OH (Scheme 2, iii). Co{U+1D35}{U+1D35}{U+1D35}(ttp)Br gives Co{U+1D35}{U+1D35}{U+1D35}(ttp)OH by ligand substitution with KOH and Co{U+1D35}{U+1D35}{U+1D35}(ttp)OH regenerates the catalyst Co{U+1D35}{U+1D35}(ttp) (Scheme 1, iii-iv). The solvent (THF or {U+2071}PrOH) and H₂O are the hydrogen sources for the catalytic dehalogenation of aryl bromides by Co{U+1D35}{U+1D35}(ttp). / Scheme 2 Mechanism of Catalytic Dehalogentaion of ArBr by CoII(ttp) in Alkaline Media / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Liu, Chunran. / "October 2012." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves ). / Abstracts also in Chinese. / Chapter Table of Contents --- p.i / Chapter Acknowledgements --- p.iv / Chapter Abbreviations --- p.v / Chapter Abstract --- p.vi / Chapter Part I --- The Base-promoted Aryl Bromine Bond Cleavage of Aryl Bromides by Cobalt(II) Porphyrins / Chapter Chapter 1 --- General Introduction --- p.1 / Chapter 1.1 --- Introduction to Porphyrins and Group 9 metalloporphyrins --- p.1 / Chapter 1.1.1 --- Porphyrin Ligand --- p.1 / Chapter 1.1.2 --- Group 9 metalloporphyrins --- p.2 / Chapter 1.1.3 --- Chemistry of Group 9 Metalloporphyrin --- p.3 / Chapter 1.1.3.1 --- Chemsitry of M{U+1D35}(por) --- p.3 / Chapter 1.1.3.2 --- Chemsitry of M{U+1D35}{U+1D35}(por) --- p.4 / Chapter 1.1.3.3 --- Chemsitry of M{U+1D35}{U+1D35}{U+1D35}{U+1D35}(por) --- p.4 / Chapter 1.1.3.4 --- Chemsitry of M{U+1D35}{U+1D35}{U+1D35}{U+1D35}(por)OH --- p.6 / Chapter 1.2 --- Physical Properties of Aryl Halides --- p.9 / Chapter 1.3 --- Synthesis of Metalloporphyrin Aryl --- p.10 / Chapter 1.4 --- Modes of Reactivity of Aryl Carbon-Halogen Bond Cleavage by Transition Metal Complexes --- p.11 / Chapter 1.4.1 --- Oxidative Addition (OA) --- p.11 / Chapter 1.4.2 --- Nucleophilic Aromatic Substitution (SNA) --- p.14 / Chapter 1.4.3 --- Halogen Atom Transfer (HXA) --- p.14 / Chapter 1.4.4 --- Radical ipso-Substitution --- p.15 / Chapter 1.5 --- Scope of Part I --- p.16 / Chapter Chapter 2 --- Base-promoted Aryl Bromine Bond Cleavage of Aryl Bromides by Cobalt(II) Porphyrins / Chapter 2.1 --- Introduction --- p.17 / Chapter 2.2 --- Objectives of the Work --- p.18 / Chapter 2.3 --- Preparation of Starting Materials --- p.18 / Chapter 2.3.1 --- Synthesis of Porphyrin --- p.18 / Chapter 2.3.2 --- Synthesis of Cobalt(II) Porphyrin --- p.18 / Chapter 2.3.3 --- Synthesis of Co{U+1D35}{U+1D35}{U+1D35}(ttp)Br --- p.19 / Chapter 2.4 --- Discovery of Ph-Br Bond Cleavage by Co{U+1D35}{U+1D35}(ttp) with KOH --- p.19 / Chapter 2.5 --- Optimization of Reaction Conditions --- p.20 / Chapter 2.5.1 --- {U+1D57}BuOH Effect --- p.20 / Chapter 2.5.2 --- Solvent Effect --- p.21 / Chapter 2.5.3 --- Temperature Effect --- p.21 / Chapter 2.5.4 --- Base Loading Effect --- p.22 / Chapter 2.6 --- Summary of Optimization of the Base-promoted Ph-Br Bond Cleavage by Co{U+1D35}{U+1D35}(ttp) --- p.22 / Chapter 2.7 --- Porphyrin Ligand Effect --- p.23 / Chapter 2.8 --- Substrate Scope of Aryl Bromides --- p.24 / Chapter 2.9 --- Mechanistic Studies --- p.25 / Chapter 2.9.1 --- Possible Pathways of Ar-Br Bond Cleavage --- p.25 / Chapter 2.9.1.1 --- Oxidative Addition (OA) --- p.26 / Chapter 2.9.1.2 --- Nucleophilic Aromatic Substitution (SNA) --- p.27 / Chapter 2.9.1.3 --- Radical ipso-Substitution --- p.28 / Chapter 2.9.1.4 --- Halogen Atom Transfer (HXA) --- p.28 / Chapter 2.9.2 --- Electronic Effect of 4-Substituted ArBr by Hammett Plot --- p.29 / Chapter 2.9.3 --- Proposed Mechanism --- p.32 / Chapter 2.9.4 --- Evidence for Halogen Atom Transfer --- p.33 / Chapter 2.10 --- Conclusion --- p.35 / Chapter Chapter 3 --- Experimental Section --- p.36 / Reference --- p.53 / Chapter Part II --- Catalytic Hydrodehalogenation of Aryl Bromides by Cobalt(II) Porphyrin in Alkaline Conditions / Chapter Chapter 4 --- General Introduction --- p.58 / Chapter 4.1 --- Introduction --- p.58 / Chapter 4.1.1 --- Properties of Halogenated Aromatic Compounds --- p.58 / Chapter 4.1.2 --- Reactivity of Aryl Carbon-Halogen Bond --- p.59 / Chapter 4.2 --- Hydrodehalogenation of Aryl Halides by Transiton Metal Complexes --- p.59 / Chapter 4.2.1 --- Molecular Hydrogen (H₂) --- p.60 / Chapter 4.2.2 --- Alcohols and Metal Alkoxides --- p.61 / Chapter 4.2.3 --- Dimethyformamide (DMF) --- p.64 / Chapter 4.2.4 --- Hydrazine (NH₂-NH₂) --- p.65 / Chapter 4.2.5 --- Metal Hydrides --- p.65 / Chapter 4.2.6 --- Alkyl Grignard Reagents --- p.67 / Chapter 4.2.7 --- Formic Acid and Its Salts --- p.67 / Chapter 4.3 --- Common Reducing Agents --- p.69 / Chapter 4.3 --- Scope of Part II --- p.69 / Chapter Chapter 5 --- Catalytic Hydrodehalogenation of Aryl Bromides by Cobalt(II) Porphyrin in Alkaline Conditions / Chapter 5.1 --- Introduction --- p.70 / Chapter 5.2 --- Objectives of the Work --- p.71 / Chapter 5.3 --- Optimization of Reaction Conditions --- p.71 / Chapter 5.3.1 --- Solvent Effect --- p.71 / Chapter 5.3.2 --- Temperature Effect --- p.72 / Chapter 5.3.3 --- Base Loading Effect --- p.73 / Chapter 5.3.4 --- Porphyrin Loading Effect --- p.73 / Chapter 5.3.5 --- Atmosphere Effect --- p.74 / Chapter 5.4 --- Summary of Optimization of Hydrodehalogention of Aryl Bromides by Co{U+1D35}{U+1D35}(ttp) --- p.74 / Chapter 5.5 --- Substrate Scope of Aryl Bromides --- p.75 / Chapter 5.5.1 --- THF as the Solvent --- p.75 / Chapter 5.5.2 --- {U+2071}PrOH as the Solvent --- p.76 / Chapter 5.6 --- Catalytic Reactivity of Co{U+1D35}{U+1D35}(ttp) as the Catalyst --- p.77 / Chapter 5.7 --- Mechanistic Studies --- p.78 / Chapter 5.7.1 --- Proposed Mechanism of Hydrodehalogenation of Aryl Bromides by Co{U+1D35}{U+1D35}(ttp) --- p.78 / Chapter 5.7.2 --- Hydrogen Source Investigation --- p.80 / Chapter 5.8 --- Conclusion --- p.83 / Chapter Chapter 6 --- Experimental Section --- p.84 / Reference --- p.92 / Chapter Appendix --- Appendix I --- p.101 / Appendix II --- p.112 / Appendix III --- p.118
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The chemistry of vitamin B₁₂Firth, R. A. January 1967 (has links)
No description available.
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A study of the outer sphere interaction of some octahedral coordinated cobalt (III) complexes by 59Co nuclear magnetic resonance methods.January 1992 (has links)
by Chung Sai Cheong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1993. / Includes bibliographical references (leaves 94-99). / DESCRIPTIVE NOTE / ABSTRACT --- p.iii / ACKNOWLEDGEMENTS --- p.v / Chapter CHAPTER ONE: --- INTRODUCTION --- p.1 / Chapter CHAPTER TWO: --- EXPERIMENTAL --- p.6 / Chapter 2.1 --- Synthesis --- p.6 / Chapter 2.2 --- NMR Measurement --- p.6 / Chapter 2.2.1 --- Solid State 59Co NMR --- p.6 / Chapter 2.2.2 --- Solution NMR --- p.7 / Chapter 2.2.2.1 --- 59Co NMR Measurements --- p.7 / Chapter 2.2.2.2 --- 13C NMR Measurements --- p.8 / Chapter 2.3 --- UV-Vis Spectral Measurements --- p.9 / Chapter 2.4 --- Computer Simulation --- p.10 / Chapter CHAPTER THREE: --- QUANTITATIVE CORRELATION OF SHIELDING ANISOTROPY AND NQCC - APPLICATION TO SOLVATION STUDIES OF OCTAHEDRAL COBALT (III)COMPLEXES / Chapter 3.1 --- Introduction --- p.11 / Chapter 3.2 --- Theory --- p.15 / Chapter 3.3 --- Results and Discussion --- p.20 / Chapter 3.3.1 --- The 59Co NMR Powder Spectrum of Diamagnetic Cobalt Complexes --- p.20 / Chapter 3.3.2 --- The Correlation of NQCC with Chemical Shift Anisotropy in the Solid State --- p.34 / Chapter 3.3.3 --- Application of Equation 3.16in Solution Studies --- p.39 / Chapter 3.3.3.1 --- The Chemical Shift --- p.39 / Chapter 3.3.3.2 --- The Effective Correlation Time --- p.48 / Chapter 3.3.3.3 --- The Nuclear Quadrupole Coupling Constant --- p.49 / Chapter 3.4 --- Summary --- p.51 / Chapter CHAPTER FOUR: --- 59Co AND 13C RELAXATION OF Co(acac)3 IN HYDROGEN BONDING (KALOMETHANE) SOLVENTS / Chapter 4.1 --- Introduction --- p.53 / Chapter 4.2 --- Results and Discussion --- p.57 / Chapter 4.2.1 --- The Static NMR Powder Spectrum Co(acac)3 --- p.57 / Chapter 4.2.2 --- Chemical shift --- p.60 / Chapter 4.2.3 --- Relaxation --- p.67 / Chapter 4.2.3.1 --- The 13C Relaxation --- p.67 / Chapter 4.2.3.2 --- The 59Co Relaxation --- p.71 / The Spin Rotation Interaction --- p.71 / The Temperature Behaviour of Relaxa- tion Rate --- p.72 / The Nuclear Quadru- pole Coupling Constant --- p.76 / The Correlation Time --- p.82 / Chapter 4.3 --- Summary --- p.90 / Chapter CHAPTER FIVE: --- CONCLUSION --- p.91 / REFERENCES --- p.94
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Synthesis and characterization of novel materials for electrochemical devicesRamachandran, Kartik 08 August 1996 (has links)
Graduation date: 1997
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Synthesis and characterization of cobalt ferrite spinel nanoparticles doped with erbiumCripps, Chala Ann 05 1900 (has links)
No description available.
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Synthesis and characterization of LiNi0.6Mn0.35Co0.05O2 and Li2FeSiO4/C as electrodes for rechargeable lithium ion batteryHong, Pengda., 洪鹏达. January 2011 (has links)
The rechargeable lithium ion batteries (LIB) are playing increasingly
important roles in powering portal commercial electronic devices. They
are also the potential power sources of electric mobile vehicles. The first
kind of the cathode materials, LiXCoO2, was commercialized by Sony
Company in 1980s, and it is still widely used today in LIB. However, the
high cost of cobalt source, its environmental unfriendliness and the safety
issue of LiXCoO2 have hindered its widespread usage today. Searching for
alternative cathode materials with low cost of the precursors, being environmentally benign and more stable in usage has become a hot topic in LIB research and development.
In the first part of this study, lithium nickel manganese cobalt oxide
(LiNi0.6Mn0.35Co0.05O2) is studied as the electrode. The materials are
synthesized at high temperatures by solid state reaction method. The effect of synthesis temperature on the electrochemical performance is
investigated, where characterizations by, for example, X-ray diffraction
(XRD) and scanning electron microscopy (SEM), for particle size distribution, specific surface area, and charge-discharge property, are done over samples prepared at different conditions for comparison. The electrochemical tests of the rechargeable Li ion batteries using
LiNi0.6Mn0.35Co0.05 cathode prepared at optimum conditions are carried out in various voltage ranges, at different discharge rates and at high temperature. In another set of experiments, the material is adopted as anode with lithium foil as the cathode, and its capacitance is tested.
In the second part of this study, the iron based cathode material is investigated. Lithium iron orthosilicate with carbon coating is synthesized
at 700℃ by solid state reaction, which is assisted by high energy ball milling. Characterizations are done for discharge capacities of the samples with different carbon weight ratio coatings. / published_or_final_version / Physics / Master / Master of Philosophy
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