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1	The Challenge of Probing Lithium Insertion Mechanisms in Cathode Materials Höwing, Jonas January 2004 (has links) <p>The Li-ion battery has, from its commercialisation in the early 1990's, now become the most widely used power source for portable low-power electronics: laptops, cellular phones and MP3-players are a few examples. To further develop existing and find new electrode materials for these batteries, it is vital to understand the lithium insertion/extraction mechanisms taking place during battery operation. In this thesis, single-crystal X-ray diffraction has been used to investigate lithium insertion/extraction mechanisms in the cathode materials V<sub>6</sub>O<sub>13</sub> and LiFePO<sub>4</sub>. A novel single-crystal electrochemical cell for <i>in situ</i> single-crystal X-ray diffraction studies has also been developed.</p><p>The phases Li<sub>3</sub>V<sub>6</sub>O<sub>13</sub> and Li<sub>3+x</sub>V<sub>6</sub>O<sub>13</sub>, 0<x<1, both contain a disordered lithium ion. A low-temperature study of Li<sub>3.24</sub>V<sub>6</sub>O<sub>13</sub> (at 95 K) shows that this disorder is static rather than dynamic; the lithium ion is equally distributed above and below an inversion centre in the centrosymmetric V<sub>6</sub>O<sub>13</sub> host structure. Short-range-ordering between this disordered lithium ion and the lithium ion inserted into Li<sub>3</sub>V<sub>6</sub>O<sub>13</sub> gives rise to solid-solution behaviour not observed earlier in the Li<sub>x</sub>V<sub>6</sub>O<sub>13</sub> system. A model is proposed for the lithium insertion mechanism up to the end-member composition Li<sub>6</sub>V<sub>6</sub>O<sub>13</sub>.</p><p>Lithium has also been electrochemically extracted from LiFePO<sub>4</sub> single crystals. On the basis of the shapes of the LiFePO<sub>4</sub> and FePO<sub>4</sub> reflections, it is concluded that FePO<sub>4</sub> is formed at the crystal surface and that the LiFePO<sub>4</sub>/FePO<sub>4</sub> interface propagates into the crystal. This is in agreement with an earlier proposed model for lithium extraction from LiFePO<sub>4</sub> particles.</p><p>Initial experiments with the newly developed single-crystal electrochemical cell for <i>in situ</i> single-crystal X-ray diffraction demonstrate that it is possible to insert lithium into a single crystal of V<sub>6</sub>O<sub>13</sub> and then collect single-crystal X-ray diffraction data. The method needs further development but promises to become a powerful tool for studying lithium insertion/extraction mechanisms.</p> Inorganic chemistry Li-ion battery cathode materials insertion mechanism single-crystal X-ray diffraction vanadium oxide lithium iron phosphate Oorganisk kemi Inorganic chemistry Oorganisk kemi
2	The Challenge of Probing Lithium Insertion Mechanisms in Cathode Materials Höwing, Jonas January 2004 (has links) The Li-ion battery has, from its commercialisation in the early 1990's, now become the most widely used power source for portable low-power electronics: laptops, cellular phones and MP3-players are a few examples. To further develop existing and find new electrode materials for these batteries, it is vital to understand the lithium insertion/extraction mechanisms taking place during battery operation. In this thesis, single-crystal X-ray diffraction has been used to investigate lithium insertion/extraction mechanisms in the cathode materials V6O13 and LiFePO4. A novel single-crystal electrochemical cell for in situ single-crystal X-ray diffraction studies has also been developed. The phases Li3V6O13 and Li3+xV6O13, 0<x<1, both contain a disordered lithium ion. A low-temperature study of Li3.24V6O13 (at 95 K) shows that this disorder is static rather than dynamic; the lithium ion is equally distributed above and below an inversion centre in the centrosymmetric V6O13 host structure. Short-range-ordering between this disordered lithium ion and the lithium ion inserted into Li3V6O13 gives rise to solid-solution behaviour not observed earlier in the LixV6O13 system. A model is proposed for the lithium insertion mechanism up to the end-member composition Li6V6O13. Lithium has also been electrochemically extracted from LiFePO4 single crystals. On the basis of the shapes of the LiFePO4 and FePO4 reflections, it is concluded that FePO4 is formed at the crystal surface and that the LiFePO4/FePO4 interface propagates into the crystal. This is in agreement with an earlier proposed model for lithium extraction from LiFePO4 particles. Initial experiments with the newly developed single-crystal electrochemical cell for in situ single-crystal X-ray diffraction demonstrate that it is possible to insert lithium into a single crystal of V6O13 and then collect single-crystal X-ray diffraction data. The method needs further development but promises to become a powerful tool for studying lithium insertion/extraction mechanisms. Inorganic chemistry Li-ion battery cathode materials insertion mechanism single-crystal X-ray diffraction vanadium oxide lithium iron phosphate Oorganisk kemi Inorganic chemistry Oorganisk kemi
3	The Investigation of Reactions of Atomic Metal Anions with Small Hydrocarbons and Alcohols in the Gas Phase Halvachizadeh, Jaleh 21 February 2014 (has links) Hydrocarbons are an abundant resource of carbon and hydrogen. For example, fossil can be used to produce useful organic compounds. However hydrocarbons seem to be inert. Thus, the activation of the C-H bond is a popular research area. Metals play the main role in most catalysts that convert hydrocarbons to starting materials in industry. The study of metals is important because the properties of the metal core greatly influences the reactivity of a catalyst.1 The study of the chemistry of metals in the gas phase provides valuable information about the properties of metals. This information can be expanded to the chemistry of metals in the condensed phase. Furthermore, it is often both more accurate and more manageable to study the profile of a reaction in the gas phase than in the condensed phase.2,3 There are many studies about metal cations in the gas phase due to ease of their production. However metals have low electronegativity, limiting the study of gas phase metal anions. Recently, a simple and efficient method to generate atomic metal anions was developed at the University of Ottawa in Dr. Mayer's research laboratory.4-6 Atomic metal anions of Fe-, Co-, Cu-, Ag-, Cs- and K- were generated in an electrospray ionization (ESI) source of a mass spectrometer (MS). In this thesis study generated metal anions were reacted with small hydrocarbons of pentane, 1-pentene, 2-pentene and 1-pentyne to investigate the role of different metal anions in the activation of the C-H bond. Also metal anions were reacted with small alcohols of 1-butanol, 2-butanol and 2-methyl-2-propanol to compare the results. Metal anions showed a variety of reactions with these hydrocarbons and alcohols. Fe- was the only metal anion to show the electron transfer reaction, indicating that alcohols are more electronegative than Fe- and less electronegative than other metal anions. Fe-, Co- and Ag- showed the complex formation reaction. All metal anions showed the deprotonation reaction. A deprotonation reaction follows the harpoon mechanism, the long range proton abstraction7, and depends on the gas phase acidity of fragments. The most informative reaction observed was the dehydrogenation reaction because a metal-containing fragment is observed as a product in the spectrum of this reaction. The observation of a metal-containing fragment in the spectrum is significant because it emphasizes the important role that metal anions play in this reaction. This suggests that a dehydrogenation reaction involves metal insertion into a C-H bond. Among the transition metal anions, it was observed that Fe- and Cu- are more reactive than Co- and Ag- with regards to the dehydrogenation reaction, probably because Fe- and Cu- have a greater hydrogen affinity than Co- and Ag- that facilitates the hydrogen abstraction reaction. Another reason could be that Fe- and Cu- have a greater gas phase acidity that leads to a more stable intermediate in the course of the reaction. The results of this thesis study revealed that Cs- and K- could not abstract H from these substrates, probably due to the absence of occupied d orbitals that would facilitate insertion into a C-H bond. Some metal anions not only can insert into a C-H bond of alcohols but also can insert into a C-O bond of alcohols to form metal hydroxide anions. Alcohols are more reactive than hydrocarbons with regards to reactions with metal anions because they contain a functional group. This thesis study shows that some atomic metal anions are able to activate the C-H bond and abstract two hydrogens to form a double bond in hydrocarbons. It is probable that the electronic configuration, gas phase acidity and hydrogen affinity of the metal anions governs their reactivity. Metal anions Mass spectrometry Metal dihydride anion Metal hydride anion Metal hydroxide anion Metal insertion mechanism Activation of C-H bond Bisdehydrogenation Collision cell CID Dehydrogenation Deprotonation ESI Enthalpy Gas phase Gas phase acidity Dissociation of deprotonated alcohol Hydrogen affinity Reactions in gas phase Reactions of metal anions Spontaneous dissociation in gas phase Triple quadrupole
4	The Investigation of Reactions of Atomic Metal Anions with Small Hydrocarbons and Alcohols in the Gas Phase Halvachizadeh, Jaleh January 2014 (has links) Hydrocarbons are an abundant resource of carbon and hydrogen. For example, fossil can be used to produce useful organic compounds. However hydrocarbons seem to be inert. Thus, the activation of the C-H bond is a popular research area. Metals play the main role in most catalysts that convert hydrocarbons to starting materials in industry. The study of metals is important because the properties of the metal core greatly influences the reactivity of a catalyst.1 The study of the chemistry of metals in the gas phase provides valuable information about the properties of metals. This information can be expanded to the chemistry of metals in the condensed phase. Furthermore, it is often both more accurate and more manageable to study the profile of a reaction in the gas phase than in the condensed phase.2,3 There are many studies about metal cations in the gas phase due to ease of their production. However metals have low electronegativity, limiting the study of gas phase metal anions. Recently, a simple and efficient method to generate atomic metal anions was developed at the University of Ottawa in Dr. Mayer's research laboratory.4-6 Atomic metal anions of Fe-, Co-, Cu-, Ag-, Cs- and K- were generated in an electrospray ionization (ESI) source of a mass spectrometer (MS). In this thesis study generated metal anions were reacted with small hydrocarbons of pentane, 1-pentene, 2-pentene and 1-pentyne to investigate the role of different metal anions in the activation of the C-H bond. Also metal anions were reacted with small alcohols of 1-butanol, 2-butanol and 2-methyl-2-propanol to compare the results. Metal anions showed a variety of reactions with these hydrocarbons and alcohols. Fe- was the only metal anion to show the electron transfer reaction, indicating that alcohols are more electronegative than Fe- and less electronegative than other metal anions. Fe-, Co- and Ag- showed the complex formation reaction. All metal anions showed the deprotonation reaction. A deprotonation reaction follows the harpoon mechanism, the long range proton abstraction7, and depends on the gas phase acidity of fragments. The most informative reaction observed was the dehydrogenation reaction because a metal-containing fragment is observed as a product in the spectrum of this reaction. The observation of a metal-containing fragment in the spectrum is significant because it emphasizes the important role that metal anions play in this reaction. This suggests that a dehydrogenation reaction involves metal insertion into a C-H bond. Among the transition metal anions, it was observed that Fe- and Cu- are more reactive than Co- and Ag- with regards to the dehydrogenation reaction, probably because Fe- and Cu- have a greater hydrogen affinity than Co- and Ag- that facilitates the hydrogen abstraction reaction. Another reason could be that Fe- and Cu- have a greater gas phase acidity that leads to a more stable intermediate in the course of the reaction. The results of this thesis study revealed that Cs- and K- could not abstract H from these substrates, probably due to the absence of occupied d orbitals that would facilitate insertion into a C-H bond. Some metal anions not only can insert into a C-H bond of alcohols but also can insert into a C-O bond of alcohols to form metal hydroxide anions. Alcohols are more reactive than hydrocarbons with regards to reactions with metal anions because they contain a functional group. This thesis study shows that some atomic metal anions are able to activate the C-H bond and abstract two hydrogens to form a double bond in hydrocarbons. It is probable that the electronic configuration, gas phase acidity and hydrogen affinity of the metal anions governs their reactivity. Metal anions Mass spectrometry Metal dihydride anion Metal hydride anion Metal hydroxide anion Metal insertion mechanism Activation of C-H bond Bisdehydrogenation Collision cell CID Dehydrogenation Deprotonation ESI Enthalpy Gas phase Gas phase acidity Dissociation of deprotonated alcohol Hydrogen affinity Reactions in gas phase Reactions of metal anions Spontaneous dissociation in gas phase Triple quadrupole
5	Investigations into cyclopropanation and ethylene polymerization via salicylaldiminato copper (II) complexes Boyd, Ramon Cornell 23 January 2007 Two distinct overall research objectives are in this Masters thesis. Very little relates the two chapters apart from the ligands. The first chapter addresses diastereoselective homogeneous copper catalyzed cyclopropanation reactions. Cyclopropanation of styrene and ethyl diazoacetate (EDA) is a standard test reaction for homogeneous catalysts. Sterically bulky salicylaldimine (SAL) ligands should select for the ethyl trans-2-phenylcyclopropanecarboxylate diastereomer. Steric bulk poorly influences trans:cis ratios. Salicylaldiminine ligands do not posses the correct symmetry to affect diastereoselectivity. The SAL ligand belongs to the Cs point group in the solid state. Other ligand motifs are more effective at altering the trans:cis ratios. The second chapter addresses the general route toward successful copper(II) ethylene polymerization catalysts. Catalytic activity of the copper(II) complexes is very low. Polymer chain growth from a copper catalyst is very unlikely. Copper-carbon bonds decompose by homolytic cleavage or C-H activation. Copper-alkyls and aryls readily decompose into brown colored oils and salts with different colors. Ligand transfer to trimethylaluminum (TMA) appears to explain low yield ethylene polymerization. bulky migratory insertion mechanism coordination/insertion methodology d-block metal late transition metal phenolic ring coordination number ketimine precatalysts ketimine nitrogen bis(salicylaldiminato)copper(II) ratio cyclopropane steric bulk salicylaldiminato TMA salt trimethylaluminum aryl oil alkyl copper-aryls copper-alkyls C-H activation homolytic homolytic cleavage copper(II) polymerization ethylene cis trans symmetry diastereomer salicylaldimine SAL EDA ethyl diazoacetate styrene cyclopropanation copper diastereoselective steric protection stable CH(SiMe3)2 intermediate catalytic activity associated TMA free TMA vacant coordination site hydrolysis Lewis acid halogen anionic anionic ligand donor ligand monodentate anionic ligand aluminum(III) monodentate polymer chain polymer chain aluminum-carbon bond bulky SAL ligand open coordination site first row transition metal PE paramagnetic high molecular weight polyethylene alkylate methylaluminoxane MAO anionic ligands arylate aluminum carbon aluminum carbon bond beta-hydrogen elimination beta hydrogen elimination Aufbau reaction Aufbau neutral dialkyl aluminum aluminum-alkyl aluminum alkyl copper(0)
6	Investigations into cyclopropanation and ethylene polymerization via salicylaldiminato copper (II) complexes Boyd, Ramon Cornell 23 January 2007 (has links) Two distinct overall research objectives are in this Masters thesis. Very little relates the two chapters apart from the ligands. The first chapter addresses diastereoselective homogeneous copper catalyzed cyclopropanation reactions. Cyclopropanation of styrene and ethyl diazoacetate (EDA) is a standard test reaction for homogeneous catalysts. Sterically bulky salicylaldimine (SAL) ligands should select for the ethyl trans-2-phenylcyclopropanecarboxylate diastereomer. Steric bulk poorly influences trans:cis ratios. Salicylaldiminine ligands do not posses the correct symmetry to affect diastereoselectivity. The SAL ligand belongs to the Cs point group in the solid state. Other ligand motifs are more effective at altering the trans:cis ratios. The second chapter addresses the general route toward successful copper(II) ethylene polymerization catalysts. Catalytic activity of the copper(II) complexes is very low. Polymer chain growth from a copper catalyst is very unlikely. Copper-carbon bonds decompose by homolytic cleavage or C-H activation. Copper-alkyls and aryls readily decompose into brown colored oils and salts with different colors. Ligand transfer to trimethylaluminum (TMA) appears to explain low yield ethylene polymerization. bulky migratory insertion mechanism coordination/insertion methodology d-block metal late transition metal phenolic ring coordination number ketimine precatalysts ketimine nitrogen bis(salicylaldiminato)copper(II) ratio cyclopropane steric bulk salicylaldiminato TMA salt trimethylaluminum aryl oil alkyl copper-aryls copper-alkyls C-H activation homolytic homolytic cleavage copper(II) polymerization ethylene cis trans symmetry diastereomer salicylaldimine SAL EDA ethyl diazoacetate styrene cyclopropanation copper diastereoselective steric protection stable CH(SiMe3)2 intermediate catalytic activity associated TMA free TMA vacant coordination site hydrolysis Lewis acid halogen anionic anionic ligand donor ligand monodentate anionic ligand aluminum(III) monodentate polymer chain polymer chain aluminum-carbon bond bulky SAL ligand open coordination site first row transition metal PE paramagnetic high molecular weight polyethylene alkylate methylaluminoxane MAO anionic ligands arylate aluminum carbon aluminum carbon bond beta-hydrogen elimination beta hydrogen elimination Aufbau reaction Aufbau neutral dialkyl aluminum aluminum-alkyl aluminum alkyl copper(0)

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