Thesis (Ph.D.)--University of Ottawa, 2008. / Includes bibliographies.

Thesis (Ph. D.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (M.S.)--Brigham Young University. Dept. of Chemistry and Biochemistry, 2005. / Includes bibliographical references.

Orientador: Mario de Jesus Mendes / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-17T06:25:56Z (GMT). No. of bitstreams: 1 Guimaraes_PauloRobertoBritto_M.pdf: 5309423 bytes, checksum: aa92c3d0424e0c6594e206702de2cbbe (MD5) Previous issue date: 1991 / Resumo: Neste trabalho foram estudadas as modificações introduzidas nas propriedades dos catalisadores de Paládio em função do teor de 'LA' 'O IND. 3' (óxido de Lantânio) presente nos mesmos. Para tanto foram preparados catalisadores de 5% Pd/'AL IND. 2' 'O IND. 3', 5% Pd-1% 'La IND. 2' 'O IND. 3'/ 'AL IND. 2' 'O IND. 3', 5% Pd/'AL IND. 2' 'O IND. 3'-'LA IND. 2' 'O IND. 3'. O método de preparação utilizado foi o da impregnação por via seca, tendo-se usado o Pd'CL IND.2', dissolvido em HCl 1N, como precursor. Após secagem a 393 K ('120 GRAUS'C) por 12h, e calcinação a 773 K ('500 GRAUS'C) por 4h, os catalisadores foram caracterizados através dos métodos de B.E.T., T.P.R., T.P.D., Quimissorção Seletiva de 'H IND. 2', Espectroscopia de Infra-vermelho, X.P.S.(E.S.C.A.), Difração de Raios-X, e um teste de atividade, através da hidrogenação do Etileno ('C IND. 2' 'H IND. 4'). Os resultados experimentais obtidos demonstraram que um alto teor de 'LA IND. 2' 'O IND. 3' modifica significativamente os perfis de redução e de dessorção de 'H IND. 2' dos catalisadores de Paládio, além de inibir fortemente a quimissorção de CO, não afetando, porém, a quimissorção de 'H IND. 2'. Além disso, verifica-se que as dispersçoes metálicas observadas nesses catalisadores são maiores que as obtidas naqueles com pouco (1%) ou nenhum 'LA IND. 2' 'O IND. 3'. Por fim, existem evidências de que, durante o processo de calcificação, ocorre a formação de um óxido misto contendo Paládio e Lantânio / Abstract: This work intended to study the changes observed on the properties of Palladium catalysts as a function of their 'LA IND. 2' 'O IND. 3' (Lanthanum oxide) content. The study was performed through the preparation and characterization of the following four catalysts: 5% Pd/'AL IND. 2' 'O IND. 3', 5% Pd-1% 'LA IND. 2' 'O IND. 3'/ 'AL IND. 2' 'O IND. 3', 5% Pd/'AL IND. 2' 'O IND. 3'-'LA IND. 2' 'O IND. 3' and 5% Pd/'LA IND. 2' 'O IND. 3'. These catalysts were prepared by the incipient wetness impregnation method, with Pd'CL IND. 2', dissolved in a 1N HCl solution, being used as Palladium precursor. After being dried at 393 K ('120 GRAUS'C) for 12h, and calcined at 773 K ('500 GRAUS'C) for 4h, thecatalysts were characterized through the methods of B.E.T., T.P.R., T.P.D., Hydrogen Chemisorption, Infrared Spectroscopy, X.P.S.(E.S.C.A.), X-Ray Diffraction, and an activity testm through ethylene ('C IND. 2' 'H IND. 4') hydrogenation. The experimental data obtained showed that a high 'LA IND. 2' 'O IND. 3' content greatly alters the Palladium catalysts reduction and 'H IND. 2' desorption profiles, and improves Pd dispersion. Furthermore, it inhibits CO chemisorption, although it does not affect 'H IND. 2' chemisorption. Besides, these data bring evidence of the formation of a mixed oxide of Lanthanum and Palladium, during the catalyst calcinations process / Mestrado / Mestre em Engenharia Química

This thesis covers an investigation of the use of pyrazolyl palladium complexes as Heck and Suzuki coupling catalysts. It is organised into four chapters. Chapter 1 is a review of the relevant literature and therefore does not cover any new work. Chapters 2 and 3 describe the synthesis and characterization of palladium complexes and testing as Heck and Suzuki coupling catalysts respectively. Chapter 4 is a summary of conclusions and future work. The subsequent section provides the main findings in chapters 2, 3 and 4. Chapter 2 is on the synthesis and characterization of palladium complexes that were used to catalyse the Heck and the Suzuki coupling reactions. The poly(pyrazol-1-ylmethyl)benzene ligands were prepared from reactions in which bis(bromomethyl)benzene with bromo substituents in different positions were reacted with either 3,5-dimethylpyrazole or 3,5-ditertiarybutylpyrazole. The products formed from these reactions were: {(3,5-Me2pzCH2)4-1,2,4,5-C6H4} (L1), {(3,5-Me2pzCH2)2}2-1,4-C6H4 (L2), {(3,5-tBu2pzCH2)2-1,4-C6H4} (L3), {(3,5-Me2pzCH2)2}2-1,3-C6H4 (L4), and {(3,5-Me2pzCH2)2}2-1,2-C6H4 (L4). Compounds L1-L5 were subsequently used to prepare their corresponding palladium complexes C1-C8, by reacting the poly(pyrazol-1-ylmethyl)benzene ligands L1-L5 with [PdCl2(NCMe)2] or [PdClMe(COD)] to form the tetranuclear palladium complex [{Pd2Cl(3,5-Me2pzCH2)4-1,2,4,5-C6H4}2] (C1), or dinuclear palladium complexes [{Pd2(μ-Cl)2X2(3,5-Me2pzCH2)2-1,4-C6H4}] (X = Cl (C2), Me (C6)), [{Pd2(μ-Cl)2Cl2(3,5-tBu2pzCH2)2-1,4-C6H4}] (C3), [{Pd2ClX(3,5-Me2pzCH2)2-1,3-C6H4}2] (X = Cl (C4), Me (C8), [{Pd2ClX(3,5-Me2pzCH2)2-1,2-C6H4}2] {X = Cl (C5), Me (C7)}, All the compounds were characterized by multinuclear NMR and elemental analysis. The structures of C1, C5 and C7 were confirmed by single crystal X-ray structural analysis. Chapters 3 and 4 describe the use of new palladium complexes prepared in this project as catalysts in Heck and Suzuki cross coupling reactions. The complexes efficiently catalysed the Heck coupling reactions which involved the coupling of iodobenzene and butylacrylate to produce trans-butyl cinnamate at 80 oC, with over 80 % conversion found within 6 h, and over 90 % within 24 h. The Suzuki coupling reactions between iodobenzene and phenylboronic acid were also performed at 80 oC. The Suzuki coupling reactions were not as efficient as the Heck coupling reactions and conversions of more than 70 % could only be reached after 24 h. Complex C6 gave the highest conversions in both the Heck and the Suzuki coupling reactions, with Heck coupling conversions of 100 % within 6 h and Suzuki coupling conversion of 73 % within 24. The major significant finding in using these palladium complexes in the two coupling reactions is that they perform both reactions at a much lower temperature (80 oC) compared to the normal temperatures of 120-160 oC used in such reaction. / Professor James Darkwa

D.Sc. (Chemistry) / The aim of this study was directed towards the stereo- and regiospecific introduction of carbon nucleophiles onto the 1- and 4-positions of glycopyranosides, since these chiral molecules contain the tetrahidropyran skeleton of a wide range of biologically active compounds (example the carpenter bee pheromone or the civit cat pheromone) or substructures of more complex natural products, such as the ionophore antibiotics indanomycin and zincophorin. Two appraoches for the introduction of carbon substituents onto the 1- and/or 4-positions of unsaturated glycopyranosides were investigated ...

M.Sc. / The main objective of this study was to identify and optimise the homogeneous catalytic systems for Pd(II) catalysed alkene acetoxylation in acetic acid to directly yield allyl or vinyl acetates as opposed to the usual aldehydes or ketones. Part of the intention of this study was to investigate potentially suitable re-oxidants and reaction conditions suitable for industrial application. The synthesis of butenyl acetate (via 1-butene acetoxylation) in particular is regarded as a potential value-adding opportunity for solvents producers. For safety considerations the study was performed with liquid alkenes (cyclohexene, cyclopentene, cycloheptene, cyclooctene and 1-hexene). Cyclohexene was used for the bulk of these studies. One of the most important and pioneering reactions in this field is the similar system for the oxidation of alkenes to ketones (the Wacker process). The related reaction, oxidative acetoxylation, is the result of the discovery of the Wacker process. The problems associated with both these reactions is the difficulty in re-oxidising the catalyst Pd once it has been reduced in the catalytic process from Pd(II) to Pd(0). Various reaction systems have been developed to improve these processes. Some of the systems that have been developed in the acetoxylation of alkenes were investigated. From the studies it has become obvious that for ease of Pd(0) re-oxidation a co-catalyst, benzoquinone, is essential for the catalytic process. This system employing a co-catalyst required another oxygen efficient re-oxidant to oxidize hydroquinone once reduced from benzoquinone in the oxidation of Pd(0). The re-oxidant would in turn be oxidized by oxygen. Various types of re-oxidants such as Cu(II) salts, heteropolyacids and metal macrocycles (e.g. Schiff base complexes and phthalocyanine metal complexes) were investigated in the multi-step electron transfer process. The most promising of the systems was the Pd(OAc)2/ benzoquinone/ heteropolyacid (H5PMo10V2O40 .34H2O)/ O2 system. From the studies it was apparent that the type of the re-oxidant can influence the yield of the product. Various other parameters were found to influence the reaction outcome. The type of Pd(II) salt was found to be influential in the reaction, for instance Pd(OAc)2 was found to be a better catalyst than Pd(CF3CO2)2. The catalyst loading was found to improve the yield iv when increased whilst this was not trivial since Pd is expensive the system needed to have as low catalyst loading as possible. The type of alkene used dictated the rate of the reaction and the product distribution. It was found that the conditions used for cyclohexene were not transferable to other alkenes without changing certain parameters to suit the alkene in question. Cycloalkenes acetoxylation was found to proceed without the addition of the strong nucleophile additive NaOAc, whilst for 1-hexene acetoxylation the reaction did not proceed without the additive. The product distribution was found to also differ between cycloalkenes and 1-hexene. For cyclohexene the by-products observed were the disproportionation products cyclohexane and benzene. In the case of 1-hexene the by-products were 2-hexanone (the Wacker reaction) and 2-hexenes (isomerisation). The operating temperature also played a role in the reaction outcome. In some instances the increase in reaction temperature negatively affected the reaction whilst in other cases it improved the reaction. Oxygen pressure also influenced the reaction to a lesser extent, with an increase in pressure favouring the reaction.

No description available.

No description available.

The use of ligand in transition-metal catalysed reactions has had a considerable impact. The present manuscript aims at showing the influence of ligands in the palladium catalysed Suzuki-Miyaura cross-coupling reaction. In chapter one, the mechanism of this reaction will be described based on the numerous contribution published in the literature. It will be shown that the electronic and steric properties of the ligands have a huge repercussion on the catalytic activity of the metal. In the second chapter, the electronic and steric properties of the widely used Buchwald-phosphine ligand will be investigated. For this purpose, bis-carbonyl iridium(I) complexes were synthesized and their characterization allowed determining their TEP (Tolman electronic parameter) and their buried volume %V[subscript(bur)]. Then three next chapters of this thesis will focus on the syntheses and characterizations of new palladium complexes bearing N-heterocyclic carbenes (NHC). Their design was made in a view to obtain high activity in cross coupling reaction, particularly in the Suzuki-Miyaura cross coupling. Their activation under the catalytic conditions leads to the formation of palladium(0) species that can be mono- or bis-ligated. The influence of the ligand on the catalyst activity will be discussed. A palladium(II) precatalyst leading to mono-ligated active species will be described. Its activity in cross-coupling is very good, since activated and non-activated aryl chlorides could be coupled with aryl boronic acids at room temperature using low catalyst loadings. Unfortunately, the catalyst activity decreased with temperature. This result showed the fragility of the mono-ligated active species. In a view to obtain more robust catalysts that can perform high turnover numbers, new palladium(II) precatalysts bearing two ancillary ligands were developed. Mixed systems NHC- phosphites and NHC-phosphines are described. NHC-phosphites precatalysts displayed very good activity, but the phosphites are unfortunately sensitive to reaction conditions, limiting their role of active species shield. NHC-phosphine bearing complexes were highly active and could perform up to 10,000 turnovers with unactivated aryl chlorides. Very interestingly, these catalysts were also able to couple benzylchlorides and allyl chlorides with a wide range of boronic acids at very low catalyst loadings. These reactions had also the great advantage to proceed in aqueous solvents at very high substrate concentration. The activation mechanism of these complexes was investigated. Dichloropalladium(II) complexes were reduced under the catalytic conditions to lead palladium(0) species. Therein, it is shown that this reduction step was rate-determining in catalysis. Some palladium(0) intermediates xxiv were synthesized and showed good to excellent activities at low temperature under the exact same conditions. They displayed high reactivity towards oxygen and moisture and have to be handled under inert atmosphere. A particular complex had the ability to react with molecular dioxygen to form a stable peroxo-complex. Interestingly, this complex displayed excellent activity in water under aerobic conditions. This system was of great advantage since the reaction could be set up under air using cheap and user-friendly reagents displaying low toxicity. Moreover, the readily available distilled water used as solvent did not require prior degassing. Symmetrical and unsymmetrical bis-NHC palladium(0) complexes were successfully synthesized. They display excellent activity in the Suzuki-Miyaura cross coupling and turnover frequencies as high as 300 could be obtained at room temperature with unactivated arylchlorides and arylboronic acids. These complexes were also found excellent catalysts for the coupling of benzylchlorides with arylboronic acids. Mechanistic studies showed that no ligand dissociation occurred during the coupling suggesting as bis-ligated active species.