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This dissertation includes exploring two scientific challenges, where both water oxidation catalysis and NH addition to alkynes will benefit greatly from the rational design of ligands. Chapter 1: The long-term goal for scientists is to use sunlight for the energy to split water. The main target of our research is the oxidation half reaction. Water oxidation catalysts have been reported by groups of Sun and Llobet but sustainable catalysis is still impaired by catalyst deactivation. This dissertation attempts to design robust catalysts through manipulating of the apical coordination sites. Chapter 2 uses phosphorus in the primary coordination sphere to create stronger axial ligand-ruthenium bonds; Chapter 3 uses a chelating macrocyclic ligand to reduce the chance of ligand loss. Chapter 4, focuses on the hydroamination of C-C multiple bonds as the most atom-efficient method for the introducing of nitrogen atoms into organic molecules.

Understanding the seven coordination and O–O coupling pathway of the distinguished Ru-bda catalysts is essential for the development of next generation efficient water-oxidation catalysts based on earth-abundant metals. This work reports the synthesis, characterization and catalytic properties of a monomeric ruthenium catalyst Ru-bnda (H2bnda = 2,2′-bi(nicotinic acid)-6,6′-dicarboxylic acid) featuring steric hindrance and enhanced hydrophilicity on the backbone. Combining experimental evidence with systematic density functional theory calculations on the Ru-bnda and related catalysts Ru-bda (H2bda = 2,2ʹ-bipyridine-6,6ʹ-dicarboxylic acid), Ru-pda (H2pda = 1,10-phenanthroline-2,9-dicarboxylic acid), and Ru-biqa (H2biqa = (1,1ʹ-biisoquinoline)-3,3ʹ-dicarboxylic acid), we emphasized that seven coordination clearly determines presence of RuV[dbnd]O with high spin density on the ORuV[dbnd]O atom, i.e. oxo with radical properties, which is one of the necessary conditions for reacting through the O–O coupling pathway. However, an additional factor to make the condition sufficient is the favorable intermolecular face-to-face interaction for the generation of the pre-reactive [RuV[dbnd]O···O[dbnd]RuV], which may be significantly influenced by the secondary coordination environments. This work provides a new understanding of the structure–activity relationship of water-oxidation catalysts and their potential to adopt I2M pathway for O–O bond formation., QC 20210204

This dissertation includes exploring two scientific challenges, where both water oxidation catalysis and NH addition to alkynes will benefit greatly from the rational design of ligands. Chapter 1: The long-term goal for scientists is to use sunlight for the energy to split water. The main target of our research is the oxidation half reaction. Water oxidation catalysts have been reported by groups of Sun and Llobet but sustainable catalysis is still impaired by catalyst deactivation. This dissertation attempts to design robust catalysts through manipulating of the apical coordination sites. Chapter 2 uses phosphorus in the primary coordination sphere to create stronger axial ligand-ruthenium bonds; Chapter 3 uses a chelating macrocyclic ligand to reduce the chance of ligand loss. Chapter 4, focuses on the hydroamination of C-C multiple bonds as the most atom-efficient method for the introducing of nitrogen atoms into organic molecules.

This dissertation includes exploring two scientific challenges, where both water oxidation catalysis and NH addition to alkynes will benefit greatly from the rational design of ligands. Chapter 1: The long-term goal for scientists is to use sunlight for the energy to split water. The main target of our research is the oxidation half reaction. Water oxidation catalysts have been reported by groups of Sun and Llobet but sustainable catalysis is still impaired by catalyst deactivation. This dissertation attempts to design robust catalysts through manipulating of the apical coordination sites. Chapter 2 uses phosphorus in the primary coordination sphere to create stronger axial ligand-ruthenium bonds; Chapter 3 uses a chelating macrocyclic ligand to reduce the chance of ligand loss. Chapter 4, focuses on the hydroamination of C-C multiple bonds as the most atom-efficient method for the introducing of nitrogen atoms into organic molecules.

Combined organic (molecular adsorption) and inorganic (TiO2 passivation) modifications for enhancing water splitting efficiency of porous bismuth vanadate electrodes are tested. The catalytic activity of BiVO4 is increased after adsorption of a newly prepared ruthenium catalyst. TiO2 passivation and sensitization with RuP dye does not show straightforward improvements to the complex photocatalytic behaviour depending on the configuration of the (two- or three-electrode) photoelectrochemical cell, type of the experiment and sample aging. The time constant for electron transport in BiVO4 electrodes (in the range of seconds, revealed by electrochemical impedance measurements) was found to correlate with the stable photocurrent of the cells. The femtosecond transient absorption studies confirm the negligible effects of RuP on the population of the photoexcited carriers in BiVO4. The transient absorption studies also show that the processes responsible for the differences in photocurrents of the modified BiVO4 samples occur on a time scale longer than the first nanoseconds. © 2020 The Author(s), QC 20200706

γ-Valerolactone (GVL) is readily obtained by the hydrogenation of levulinic acid (LA) and is considered a sustainable platform chemical for the production of biobased chemicals. Herein, the performance and stability of Ru-based catalysts (1 wt % Ru) supported on TiO 2 (P25) and ZrO 2 (monoclinic) for LA hydrogenation to GVL is investigated in the liquid phase in batch and continuous-flow reactors using water and dioxane as solvents. Particular attention is paid to the influence of possible impurities in the LA feed on catalyst performance for LA hydrogenation. Benchmark continuous-flow experiments at extended times on-stream showed that the deactivation profiles are distinctly different for both solvents. In dioxane, the Ru/ZrO 2 catalyst is clearly more stable than Ru/TiO 2, whereas the latter is slightly more stable in water. Detailed characterization studies on spent catalysts after long run times showed that the deactivation of Ru/TiO 2 is strongly linked to the reduction of a significant amount of Ti 4+ species of the support to Ti 3+ and a decrease in the specific surface area of the support in comparison to the fresh catalyst. Ru/ZrO 2 showed no signs of support reduction and displayed morphological and structural stability; however, some deposition of carbonaceous material is observed. Impurities in the LA feed such as HCOOH, H 2SO 4, furfural (FFR), 5-hydroxymethylfurfural (HMF), humins, and sulfur-containing amino acids impacted the catalyst performance differently. The results reveal a rapid yet reversible loss of activity for both catalysts upon HCOOH addition to LA, attributed to its preferential adsorption on Ru sites and possible CO poisoning. A more gradual drop in activity is found when cofeeding HMF, FFR, and humins for both solvents. The presence of H 2SO 4, cysteine, and methionine all resulted in the irreversible

Metal complexes with oxygen donor ligands are of interest because of their relevance to the active sites of oxide-based heterogeneous catalysts. In this thesis, metal complexes with chelating oxygen-donor ligands, including the Kläui tripodal ligand [(η5-C5H5)Co{P(O)(OEt)2}3]- (LOEt-) and perfluoropincolate [(CF3)4C2O2]2- (pinF), have been synthesized, and their redox and catalytic chemistry has been studied. Also, nitrido-bridged heterometallic iron(IV)/ruthenium(IV) porphyrin complexes have been synthesized and their use as catalysts for alkene epoxidation has been examined. In Chapter 2, Ce(IV) complexes with oxidizing oxyanion ligands have been synthesized and structurally characterized. Reaction of [(LOEt)2CeCl2] with NaIO4 in water afforded a Ce(IV) periodate complex, 2-2, the crystal of which was found to contain two independent molecules: [(LOEt)2Ce(IO4)2] (2-2a) and [(LOEt)2Ce(H2O)(IO4)][IO4] (2-2b). Treatment of [(LOEt)2CeCl2] with I2O5 in CH3CN in the presence of a trace amount of water led to isolation of the Ce(IV) iodate complex [(LOEt)2Ce(IO3)2]⋅H+ICl2- (2-3). Reaction of [(LOEt)2CeCl2] with K2S2O8 in water afforded the Ce(IV) persulfate complex [(LOEt)2Ce(S2O8)] (2-4). The cyclic voltammograms of complexes 2-2 – 2-4 in acetonitrile displayed quasi-reversible couples that are attributed to the Ce(III/IV) oxidation. The Ce(IV) periodate and iodate complexes can oxidize methyl p-tolyl sulfide to sulfoxide. A Ru-im

Water oxidation as a multi-electron transfer and endothermal reaction has been considered to be the bottleneck of solar-driven water splitting into oxygen and hydrogen. Herein, an alternative approach for solar energy conversion is developed by coupling H2 generation with the selective oxidation of alcohol. In a closed redox system containing molecular ruthenium catalyst (RuCat) and Pt modified g-C3N4 (Pt-g-C3N4) composite, hydrogen production is concomitant with the oxidation of benzyl alcohols to aldehydes with over 99% selectivity in the presence of visible light and pure water. By contrary, the system lacking molecular catalyst only exhibits low to moderate selectivities towards aldehydes. The remarkably improved selectivity is attributed to the formation of highly active Ru(IV) = O intermediate through efficient hole transfer from g-C3N4 to RuCat., QC 20180227

Includes bibliographical references (leaves 126-131)., Includes abstract and appendix.

DFT calculations on the reaction mechanisms of stoichiometric organic reactions and catalytic organometallic reactions have been reported in this thesis. With the aid of DFT calculations, we have elucidated reaction mechanisms based on experimental results. In addition, interesting predictions have been made. In Chapter 2, we studied systematically the dimerization reactions of boroles in which Diels-Alder (DA) dimers, bridged-bicyclic (BB) dimers or spiro dimers (SD) are generated depending on the substituents on the borole. We investigated how different substituents at the carbon atoms of the butadiene backbone as well as at the boron atom influence the dimerization reaction pathways. The DFT results show that, in general, both the DA and BB dimers are easily accessible kinetically, and the DA dimers are thermodynamically more stable than the BB dimers. When the substituent-substituent repulsive steric interactions are alleviated to a certain extent, the BB dimers are more stable than the DA dimer, and become accessible. The SD dimers are generally kinetically difficult to obtain. However, we found that aryl substituents promote the formation of the SD dimers. In Chapter 3, we studied the reactions of borole with CO, in which Lewis acid-base adduct 1AD, tricyclic boracycle 1TB or ketene derivative 1KD are reported depending on the substituents on the borole. DFT calculations were performed to study systematically the influence of borole substituents on these reactions. It was found that the Lewis acid-base adduct 1AD is a kinetic product, and can further isomerize to ketene derivative 1KD. The Lewis acid-base adduct 1AD can also undergo ring expansion, followed-by dimerization and migrations to afford the tricyclic boracycle 1TB. The computational results show that strong electron-withdrawing perfluorophenyl substituents significantly stabilize the Lewis acid-base adduct 1AD, allowing its successful isolation. In most cases, the tricyclic boracycle 1TB is both kin

DFT calculations on the reaction mechanisms of stoichiometric organic reactions and catalytic organometallic reactions have been reported in this thesis. With the aid of DFT calculations, we have elucidated reaction mechanisms based on experimental results. In addition, interesting predictions have been made. In Chapter 2, we studied systematically the dimerization reactions of boroles in which Diels-Alder (DA) dimers, bridged-bicyclic (BB) dimers or spiro dimers (SD) are generated depending on the substituents on the borole. We investigated how different substituents at the carbon atoms of the butadiene backbone as well as at the boron atom influence the dimerization reaction pathways. The DFT results show that, in general, both the DA and BB dimers are easily accessible kinetically, and the DA dimers are thermodynamically more stable than the BB dimers. When the substituent-substituent repulsive steric interactions are alleviated to a certain extent, the BB dimers are more stable than the DA dimer, and become accessible. The SD dimers are generally kinetically difficult to obtain. However, we found that aryl substituents promote the formation of the SD dimers. In Chapter 3, we studied the reactions of borole with CO, in which Lewis acid-base adduct 1AD, tricyclic boracycle 1TB or ketene derivative 1KD are reported depending on the substituents on the borole. DFT calculations were performed to study systematically the influence of borole substituents on these reactions. It was found that the Lewis acid-base adduct 1AD is a kinetic product, and can further isomerize to ketene derivative 1KD. The Lewis acid-base adduct 1AD can also undergo ring expansion, followed-by dimerization and migrations to afford the tricyclic boracycle 1TB. The computational results show that strong electron-withdrawing perfluorophenyl substituents significantly stabilize the Lewis acid-base adduct 1AD, allowing its successful isolation. In most cases, the tricyclic boracycle 1TB is both kin

The ruthenium assisted azide-alkyne cycloaddition (RuAAC) reaction is a well-established method for the generation of 1,5- and 1,4,5-substituted 1,2,3-triazoles, which we have extended to the solid-phase synthesis of 1,2,3-triazole-peptides. The 1,2,3-triazole moieties were formed upon the reaction of alkynes with a solid-phase bound secondary azide in the presence of the Cp*RuCl(COD) catalyst at room temperature. Both terminal and internal alkynes underwent highly regioselective cycloaddition reactions under mild conditions, facilitating release of the peptide construct from the resin with intact side-chain protection. Almost quantitative conversion to the corresponding 1,2,3-triazoles was observed within 1h.

Includes bibliographical references (leaves 126-131)., Includes abstract and appendix.

DFT calculations on the reaction mechanisms of stoichiometric organic reactions and catalytic organometallic reactions have been reported in this thesis. With the aid of DFT calculations, we have elucidated reaction mechanisms based on experimental results. In addition, interesting predictions have been made. In Chapter 2, we studied systematically the dimerization reactions of boroles in which Diels-Alder (DA) dimers, bridged-bicyclic (BB) dimers or spiro dimers (SD) are generated depending on the substituents on the borole. We investigated how different substituents at the carbon atoms of the butadiene backbone as well as at the boron atom influence the dimerization reaction pathways. The DFT results show that, in general, both the DA and BB dimers are easily accessible kinetically, and the DA dimers are thermodynamically more stable than the BB dimers. When the substituent-substituent repulsive steric interactions are alleviated to a certain extent, the BB dimers are more stable than the DA dimer, and become accessible. The SD dimers are generally kinetically difficult to obtain. However, we found that aryl substituents promote the formation of the SD dimers. In Chapter 3, we studied the reactions of borole with CO, in which Lewis acid-base adduct 1AD, tricyclic boracycle 1TB or ketene derivative 1KD are reported depending on the substituents on the borole. DFT calculations were performed to study systematically the influence of borole substituents on these reactions. It was found that the Lewis acid-base adduct 1AD is a kinetic product, and can further isomerize to ketene derivative 1KD. The Lewis acid-base adduct 1AD can also undergo ring expansion, followed-by dimerization and migrations to afford the tricyclic boracycle 1TB. The computational results show that strong electron-withdrawing perfluorophenyl substituents significantly stabilize the Lewis acid-base adduct 1AD, allowing its successful isolation. In most cases, the tricyclic boracycle 1TB is both kin

This work explores the opportunity to reduce the cost and increase the stability of RuO2-based electrocatalyst for oxygen evolution reaction by coating ternary oxide RuO2-Sb2O5-SnO2 on chemically stable titanium support. An active and stable type of Ti/RuO2-Sb2O5-SnO2 dimensionally stable anodes (DSA) was studied with different mole ratios of ruthenium prepared by using thermal deposition method. The metal oxides coating layer was maintained around 15 g m-2. In this ternary oxide coating, RuO2 serves as the catalyst, SnO2 as the dispersing agent, and Sb2O5 as the dopant. The morphology by SEM showed that the compact and uniform surface morphology that indicates a favorable dispersion of species of 10%, 20% and 30% ruthenium samples. Further increase of ruthenium content, surface structure with more agglomerated particles of RuO2 and the coating surface becomes less compact. The microstructure by XRD indicates that 10%, 20% and 30% ruthenium samples well intermix with Sb2O5, when ruthenium content exceeded 50% in the active coating layer, new and noticeable peaks corresponding to ruthenium oxide appear. Effects of ruthenium content on Ti/RuO2-Sb2O5-SnO2 anodes in terms of both catalyst activity and the catalyst corrosion for oxygen evolution reaction were investigated. The electrochemical characterization of these electrodes has been performed in acid medium, and the reversibility, electrochemical porosity (related to voltammetric charge), kinetic parameters (related to Tafel measurements) and electrochemical resistance (related to electrochemical impedance spectroscopy) have been established. The best activity performances were achieved by 75% nominal ruthenium content. The value of qaqc-1 was approximately

This work explores the opportunity to reduce the cost and increase the stability of RuO2-based electrocatalyst for oxygen evolution reaction by coating ternary oxide RuO2-Sb2O5-SnO2 on chemically stable titanium support. An active and stable type of Ti/RuO2-Sb2O5-SnO2 dimensionally stable anodes (DSA) was studied with different mole ratios of ruthenium prepared by using thermal deposition method. The metal oxides coating layer was maintained around 15 g m-2. In this ternary oxide coating, RuO2 serves as the catalyst, SnO2 as the dispersing agent, and Sb2O5 as the dopant. The morphology by SEM showed that the compact and uniform surface morphology that indicates a favorable dispersion of species of 10%, 20% and 30% ruthenium samples. Further increase of ruthenium content, surface structure with more agglomerated particles of RuO2 and the coating surface becomes less compact. The microstructure by XRD indicates that 10%, 20% and 30% ruthenium samples well intermix with Sb2O5, when ruthenium content exceeded 50% in the active coating layer, new and noticeable peaks corresponding to ruthenium oxide appear. Effects of ruthenium content on Ti/RuO2-Sb2O5-SnO2 anodes in terms of both catalyst activity and the catalyst corrosion for oxygen evolution reaction were investigated. The electrochemical characterization of these electrodes has been performed in acid medium, and the reversibility, electrochemical porosity (related to voltammetric charge), kinetic parameters (related to Tafel measurements) and electrochemical resistance (related to electrochemical impedance spectroscopy) have been established. The best activity performances were achieved by 75% nominal ruthenium content. The value of qaqc-1 was approximately

This work explores the opportunity to reduce the cost and increase the stability of RuO2-based electrocatalyst for oxygen evolution reaction by coating ternary oxide RuO2-Sb2O5-SnO2 on chemically stable titanium support. An active and stable type of Ti/RuO2-Sb2O5-SnO2 dimensionally stable anodes (DSA) was studied with different mole ratios of ruthenium prepared by using thermal deposition method. The metal oxides coating layer was maintained around 15 g m-2. In this ternary oxide coating, RuO2 serves as the catalyst, SnO2 as the dispersing agent, and Sb2O5 as the dopant. The morphology by SEM showed that the compact and uniform surface morphology that indicates a favorable dispersion of species of 10%, 20% and 30% ruthenium samples. Further increase of ruthenium content, surface structure with more agglomerated particles of RuO2 and the coating surface becomes less compact. The microstructure by XRD indicates that 10%, 20% and 30% ruthenium samples well intermix with Sb2O5, when ruthenium content exceeded 50% in the active coating layer, new and noticeable peaks corresponding to ruthenium oxide appear. Effects of ruthenium content on Ti/RuO2-Sb2O5-SnO2 anodes in terms of both catalyst activity and the catalyst corrosion for oxygen evolution reaction were investigated. The electrochemical characterization of these electrodes has been performed in acid medium, and the reversibility, electrochemical porosity (related to voltammetric charge), kinetic parameters (related to Tafel measurements) and electrochemical resistance (related to electrochemical impedance spectroscopy) have been established. The best activity performances were achieved by 75% nominal ruthenium content. The value of qaqc-1 was approximately

Density Functional Theory (DFT) calculations have been widely applied to understand mechanisms of various chemical reactions. In this thesis, theoretical studies employing DFT calculations on recently discovered stoichiometric and catalytic reactions are reported. Insights into developing new reactions, selecting appropriate substrates, and designing more efficient catalytic systems are given. Part I: The first example of complete cleavage of isonitrile carbon-nitrogen triple bond without the mediation of a transition metal has been investigated. The mechanism of the reaction is found to be passing through a succession of 1,2-migrations that reduce the carbon-nitrogen π-bonds. Breaking of the strong carbon-nitrogen σ-bond is attributed to the presence of nucleophilic nitrogen atom. The influences of excess amount of tert-butyl isonitrile in resulting different products are discussed. For the analogous reaction using carbon monoxide, the reason for unsuccessful complete carbon-oxygen triple bond cleavage has been related to the poorer nucleophilicity of the oxygen atom. Part II: The reaction mechanisms for the formation of the first rhenabenzene complex Re[–C(Np)=(C(CO2Et)C(OEt)=CHC(OEt)=}(CO)4 (Np = naphthalene-1-yl) and an unexpected vinyl-substituted rhenacyclobutadiene complex Re{–C(Np)=C(C(OEt)=CH(CO2Et))C(OEt)=}(CO)4 have been studied. The results suggest that the reactions are initiated by the direct nucleophilic attack of the ethoxyethyne on a carbene carbon of the rhenacyclobutadiene complex Re{–C(Np)=(C(CO2Et)C(OEt)=}(CO)4. Energies of the lowest unoccupied molecular orbitals (LUMOs) and the charges on the carbene carbons of the rhenacyclobutadiene complexes are important in determining the reactivity and the regioselectivity of the reactions. Structural analysis and aromatic stabilization energy calculations on model metallabenzenes show that rhenabenzene complexes are aromatic in nature. Pa

The mechanism of the partial oxidation of methane has been investigated over a bimetallic Pt-Ru catalyst. Dedicated experiments aimed to separate and quantify the relative contribution of single reactions included in the so-called "combustion and reforming" mechanism using the same catalyst. The catalyst is 0.5% Ru and 0.5% Pt (w/w) supported on mixture of alumina, ceria and zirconia (75/4.4/20.6%, w/w), washcoated on a ceramic monolith. Steam reforming, dry reforming, direct and reverse water-gas shift reactions were investigated. The temperature range investigated is 300 < T < 800 degrees C, while the space velocity range is 25.000 < GHSV < 100.000 h(-1). Conditions at which single side reactions are expected to occur during the partial oxidation process, were approximated by tuning the reactant composition. The experimental results are also compared with thermodynamic equilibrium calculations. The CO and H-2 yields of partial oxidation have been quantitatively connected with steam and dry reforming, while the persistent water-gas shift reaction always rearranges the products and intermediates., QC 20100525

Ru-BEA catalysts with 1.0-2.5 wt.% Ru were prepared by ion exchange. The acidic properties of these catalysts were investigated using deuterated acetonitrile, pyridine, and 2,6-di-tert-butyl-pyridine. The deposited Ru was studied by CO-FTIR spectroscopy. The materials were tested as catalysts in the hydrogenation of a conjugated cyclic keto-enol, namely, 5-hydroxymethylene-5H-6,7-dihydrodibenzo[a,c]cyclohepten-6-one. Beside hydrogenation, hydrogenolysis products were identified by GC-MS and H-1 NMR techniques. Relations were sought between the selectivity and some physicochemical properties of the catalyst. (C) 2004 Elsevier B.V. All rights reserved.