Abstract This thesis is divided into two parts. Part one presents a novel method for the synthesis of naphthalenes bearing aryl substituents. The novel route starts from three simple and readily available tetralones, α-tetralone, 6-methoxy-α-tetralone and 6,7-dimethoxy-α- tetralone. By means of standard Suzuki coupling methodology and aromatization methods, twelve aryl-substituted naphthalenes were synthesized from the tetralones over five steps in good yields. Some of the aryl-substituted naphthalenes synthesized have shown positive results when tested against malignant cancer cells. Part one also explains how unexpected cyclopropa[a]naphthalenes were obtained from 1-aryl-3,4-dihydro-2- naphthaldehydes by treatment with lithium aluminium hydride. The methodology developed in part one is further explored in part two of the thesis, which describes the synthesis of analogues of [1,1’]binaphthalenyl-2,2’-diol. A small library of twelve different biaryl diols was prepared from simple bromo(methoxy)naphthaldehydes that were synthesized in part one. The resultant biaryl diols were used in the design of twenty-two novel phosphite, phosphate, phosphoramidite and phosphoramidate ligands in which the phosphorus atoms are contained in either a nine-or an eight-membered heteroatom ring. However, these ligands are still to be tested in metal-catalyzed hydrogenation reactions.

MSc., Faculty of Science, University of the Witwatersrand, 2011 / Gold has for many years been regarded as being inert and catalytically inactive compared to the PGMs (platinum group metals). However, in the past decade it has attracted a lot of interest as both a heterogeneous and a homogenous catalyst and has been shown to catalyse a wide range of reactions e.g. oxidation, hydrogenation and reduction among others. Highly dispersed gold nanoparticles on metal oxides, like titanium oxide (Degussa, P25) have predominantly been studied because they yield some of the most active and stable catalysts. Modification of the catalysts and/or supports has been shown to affect their catalytic properties. Likewise, perovskites, which can be manipulated by partial substitution, are reported to be active supports for CO oxidation, but only at high temperatures with no activity shown for temperatures below 200°C. In this study, these perovskites were investigated at low temperatures (below 100°C) with improved activity found upon gold deposition. The presence of gold nanoparticles therefore significantly enhanced the catalytic activity, while the support itself was suspected to be involved in the reaction mechanism. A series of perovskites of the type ABO3 (LaMnO3, LaFeO3, LaCoO3 and LaCuO3) were prepared using the citrate method, while the gold was deposited on them using the deposition-precipitation method. The supports were calcined at different temperatures for optimisation. The catalysts were tested for carbon monoxide oxidation and the active catalysts characterised by XRF, XPS, XRD, Raman spectroscopy and BET surface area measurements. With the support calcined at 800ºC, the best catalyst was then modified and compared with the unmodified catalyst. The 1-wt%Au supported on LaFeO3 was found to give the best catalytic performance. This support was then modified with various weight loadings of calcium to determine the effect of calcium on the catalytic activity. Calcium-doped materials showed decreased surface area, poorer crystallinity and a drop in catalytic activity relative to the Au-LaFeO3 which indicated the best results for CO oxidation. In addition, Au-LaFeO3 showed online stability over 21 hours. Calcining the support improved the incorporation of gold nanoparticles into the perovskite lattice, resulting in superior catalytic activity. Nevertheless, at higher calcination temperatures, the catalytic activity of Au-CaTiO3 was depressed while that of Au-LaFeO3 was enhanced. The activity of perovskites increased upon gold deposition. XPS, revealed that in the active catalysts, both cationic and metallic gold co-existed, whilst in the inactive catalysts the gold existed predominantly either as cationic or metallic gold.

PhD, Faculty of Science, University of the Witwatersrand

Thesis ( M.Sc)--University of the Witwatersrand, Faculty of Science, 2003 / Initial investigations at Mintek, into the addition of gold to commercial hopcalite (CuxMnyOz), showed that it improved the activity of hopcalite. So this study was initially focused on investigating Aulhopcalite catalysts further. Also, since according to literature, MnxOy has catalytic potential, the study of AulMnxOy catalysts was included. Au/hopcalite and Aul/nxOy catalysts were made by means of deposition-precipitation, colloidal gold deposition and co-precipitation. Only one catalyst-type was highly active at room temperature - the co-precipitated Au/MnxOy catalysts. The optimised co-precipitated Au/MnxOy catalysts were more active than all the other catalysts by at least an order of magnitude. So the study focus changed, to make the optimisation of AulMnxOy catalysts a priority. Cerium is a well-known promoter on MnxOy catalysts, and so was also added to the co-precipitated Au/MnxOy catalysts. However, even small amounts of cerium had an adverse effect on the catalysts' activities. The compaction and crushing of a co-precipitated Au/MnxOy catalyst to obtain granules of larger particle size than the powders, was also carried out. The activities and surface areas of the catalysts were found to be comparable. This augers well for industrial purposes, since the use of powdered catalysts in industry is not viable.

Thesis advisor: Chia-Kuang Tsung / In order to enhance the selectivity of metal nanoparticle heterogeneous catalysts, a method for the encapsulation of metal nanoparticles by crystalline nanoporous materials was designed and implemented through a wet-chemical, capping-agent-mediated encapsulation strategy. Two thermally and chemically stable metal organic frameworks (MOFs) with different aperture sizes were chosen as the crystalline nanoporous layers for metal nanoparticle (NP) encapsulation. Successful encapsulation and good catalytic performance depended on understanding and engineering the interface between the metal catalyst core and the nanoporous shell. After the synthesis of the NPs-MOF composite, their catalytic activity and selectivity were studied. Two kinds of capping agents (polymer and surfactant) were used to demonstrate different mechanisms for NP encapsulation. The polymer (polyvinylpyrrolidone, PVP) induced interaction between the NP surface and MOF precursors while the surfactant (cetyltrimethylammonium bromide, CTAB) controlled the alignment between the metal nanoparticles and MOFs. Furthermore, the capping-agent-directed overgrowth could be a general method of not only loading various inorganic nanoparticles into MOF single crystals but also bridging two porous materials with totally different structures. MOF shells were further functionalized by postsynthetic linker exchange. By applying the process, a new concept was introduced for the formation of enlarged pore apertures by linker dissociation during MOF linker exchange, as demonstrated by the postsynthetic encapsulation of species much larger than the pore aperture of the MOF structure. Kinetic studies of linker exchange rely on the competition between associative and dissociative linker exchange mechanisms. It was found that guest encapsulation was enhanced under conditions that favored the dissociative pathway. Through kinetics studies, linker exchange rate was also found to vary in different solvents. The different exchange rates were then used to create hierarchical porosity in MOF structure, and a double-solvent-mediated overgrowth strategy was designed to form hollow and mesoporous MOF. The results help to provide new ideas for nanopores related heterogeneous catalysis. The discussion of active metal NP cores with a nanoporous shell, as a frontier core-shell material, may benefit further study in developing highly selective catalysts. / Thesis (PhD) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

The work reported in this thesis is concerned with two separated but related studies. The first involved examination of hydrogenation reactions of alkenes, dienes and alkynes using (Rh[sub]2C1(CO)[sub]2(dppm)[sub]2JBPh[sub]4 as a catalyst. Kinetic studies have been performed on the reaction of hexene. The system only well-behaved in the presence of a base, R[sub]3N, where a rst order dependance on both catalyst and hydrogen concentations observed. The order with respect to alkene is of the Michaelis-Menton type. This behaviour suggests that the active catalyst is a neutral monohydride generated by deprotonation of a ionic dihydride. It is proposed that the active catalyst is a dinuclear species, since none of the likely mononuclear breakdown oducts shows any catalytic activity. A catalytic cycle for the reaction is proposed. The second study was an investigation into the use of fast atom bombardment (FAB) mass spectrometry as a means of anaylsis organometallic compounds which have proved difficult to identify using other ionisation modes. The technique was shown to informative spectra for a series of dinuclear rhodium-dppm mplexes and some dinuclear manganese carbonyl derivatives. FAB ionisation also proved effective for identification of phosphine and phosphite derivatives of [RCC0[sub]3(CO)[sub]9.] (R=CH[sub]3, C1). The technique was also combined with thin layer chromatography (TLC) in examining a reaction of [Mo(CO)[sub]6.] with Ph[sub]2P(CH[sub]2)[sub]2P(O)Ph[sub]2 (dppeO) which yields a mixture of seven products. It was found that good spectra of pure materials could be obtained TLC separation, followed by removal of the appropriate section silica support from the plate. This was subjected directly to FAB mass spectrometry without prior extraction of the product from silica. Using this technique, it proved possible to identify three new dppeO derivatives of [Mo(CO)[sub]4 (dppeO) derivatives of [Mo(CO)[sub]6. These are [Mo(CO)[sub]5 (dppeO)] cis-[Mo(CO)[sub]4 (dppeO)[sub]2] and [Mo[sub]2(CO)[sub] 4 (dppeO)[sub]2].

No description available.

Initial developments within group 2 chemistry led to the chemistry being described as ‘lanthanide mimetic’ however, over the last 10 years group 2 catalysis has emerged in its own right, making these comparisons unjustified. Development of this catalytic chemistry has, until now, largely focussed upon the use of protic reagents in order to achieve turnover. Reported in this thesis is the development of magnesium hydride chemistry for both stoichiometric and catalytic purposes. Reported in chapter 2 of this thesis, is the use of the pharmaceutically relevant magnesium dihydropyridide complexes and explores their use as hydride transfer reagents with respect to a representative ketone, benzophenone, whilst further study with various different isocyanate reagents with differing electronic and steric demands provides divergent reactivity. Extension of this chemistry with respect to carbodiimides provides a series of N-heterocyclic guanidinates in all but one case. The chemistry described in chapters 3-6 investigates the use of magnesium hydrides in catalysis. Using the commercially available hydridic pinacol borane (HBpin) reagent a series of catalytic reactions with respect to pyridines (chapter 3), nitriles (chapter 4), iso-nitriles (chapter 5) and heterocumulenes (chapter 6) are investigated. In each case, studies have sought to underpin the catalytic reactivity by examining the single steps of the proposed catalytic cycle via a series of stoichiometric reactions which has allowed for the isolation and characterisation of numerous potential catalytic intermediates. Monitoring of these catalytic reactions in situ with NMR spectroscopy, combined with kinetic analysis, has allowed for further information to be obtained with regards to the mechanism and calculation of the activation energy parameters associated with each reaction.

Iron β-diketiminate complexes have great potential as catalysts. Previous work into the coordination chemistry of complexes bearing the β-diketiminate ancillary ligand (Chapter 1) attest to the useful properties of these complexes in catalysis. A handful of literature reports on catalytic systems hint that this could be further extended. Hydrophosphination is a growing field that continues to generate a lot of interest from industry and academia alike. The aims of this project are to investigate hydrophosphination reactions with iron β-diketiminate complexes, to achieve high degrees of regioselectivity from these sterically encumbered complexes and to investigate iron catalysed dehydrocoupling reactions. A combination of synthetic and mechanistic methodologies will be employed in order to achieve definitive insight via NMR spectroscopic analysis, kinetic studies and solid state crystallography. Initial work presented herein (Chapter 2) will focus on the synthesis of iron(II) β-diketiminate complexes. Previously reported literature methods will be explored in order to determine an optimum procedure to use these precatalyst complexes. Initial investigations into hydrophosphination activity of these iron species will then be explored with alkenes. Results of these studies led to serendipitous findings and unexpected results in phosphine dehydrocoupling. The scope of this reactivity was then probed and mechanistic considerations taken into account with findings detailed herein. Radical catalysed reactivity observed will be further discussed. Solvent selectivity will then be discussed with a simple yet highly effective solvent change yielding a complete shift in catalytic activity. Further studies (Chapter 3) highlight the orthogonal reactivity of iron(II) β-diketiminate complexes in hydrophosphination catalysis. Less electronically activated and more atypical substrates have been investigated to determine their activity in hydrophosphination reactions. The synthesis of phosphinoalkenes and phosphinoalkynes for cyclic intramolecular hydrophosphination reactions are detailed along with their catalytic activity. Preliminary mechanistic studies are discussed with radical species again proving crucial to catalytic activity. Selective intermolecular hydrophosphination reactions have been investigated with alkynes. A solvent based switch can be employed wherein the regioselectivity of the reaction is completely altered. Substrate scope, mechanistic considerations and potential future applications are examined in full detail. Dehydrocoupling catalysis can be extended in scope (Chapter 4) from iron catalysed phosphine homocoupling reactions to heterocoupling reactions. Phosphine-silane dehydrocoupling is found to be highly selective for the formation of silaphosphanes, preliminary mechanistic insight and reaction scope is discussed. Analogous amine-silane dehydrocoupling is explored in full. The substrate scope offers insight into reactivity and potential further applications in sequential and tandem catalysis. In depth mechanistic insight is discussed with kinetic analyses. Iron-amido complexes are observed to react in a metathesis mediated cycle via iron hydride species. Finally catalytic alcohol-silane dehydrocoupling is investigated as a synthetic route to protected natural products in organic synthesis. Unsaturated silazanes are potential targets for further dehydrocoupling reactions. Catalytic reactions with pinacolborane led to highly facile desilylation reactions (Chapter 5). Mechanistic considerations hint that the reactions occur via σ-bond metathesis could through iron hydride species. Desilylation activity is then extended to siloxanes and a model developed with potential applications in the depolymerisation of polysilazanes and polysiloxanes.

by Ho-ming Leung. / Thesis (M. Phil.)--Chinese University of Hong Kong, 1982. / Bibliography: l. 63-67.