Described here are detailed kinetic studies probing the structural elements which are crucial for the catalytic activity of dinuclear Zn(II) complexes towards phosphate diester cleavage. First, two sets of dinuclear Zn(II) complexes (a member with and without a bridging oxyanion linker group) were synthesized and their ability to promote the cyclization of 2-hydroxypropyl-p-nitrophenyl phosphate, a common model for RNA, was compared. Kinetic studies indicated that the complexes without the oxyanion linker were more active in promoting the cyclization in methanol under pH controlled conditions at 25 degrees. Quantitative energetics analysis shows that the rate reduction is attributable to a decrease in the second-order rate constant for the cyclization reaction, which adds 3.7 and 6.5 kcal/mol of activation energy to the respective reactions mediated by the complex with the oxyanion linker. Secondly, we have investigated a series of dinuclear Zn(II) complexes that incorporate various substituents including hydrophobic and hydrogen-bonding ones. Analysis of the data at the pH optimum for each reaction indicates that the presence of the H-bonding groups and alkyl groups provides similar increases (at least an order of magnitude) of the kcat terms over the unfunctionalized complex. There is also no clear trend that H-bonding groups or the alkyl groups provide stronger binding to the substrate than the parent complex. We also describe here the preparation and kinetic analysis of a series of solid supported transition metal catalysts for the cleavage of P=O chemical warfare simulants and P=S pesticides. We report a kinetic study of a 1,10-phenanthroline:Zn(II) complex immobilized on macroporous polystyrene which is capable of accelerating the cleavage of G-agent and V-agent simulants in methanol at neutral and ambient temperature by up to one hundred thousand-fold. The materials are recoverable and can be recycled at least ten times. We have also devised a methodology for simple immobilization of an ortho-palladated dimethylbenzylamine complex on macroporous polystyrene and amorphous silica gel. We report the catalyst preparation and a detailed kinetic study of their catalysis of the methanolysis of five P=S pesticides at neutral and ambient temperature. The polymeric catalysts give over billion-fold acceleration compared to the uncatalyzed background reaction at the same pH. / Thesis (Ph.D, Chemistry) -- Queen's University, 2010-11-23 12:18:46.936

With continually increasing concern over anthropogenic carbon dioxide emissions and their effect on global climate, the search for alternative fuels, especially for mobile applications such as in vehicles, is of immediate concern. Herein, research towards hydrogen as an alternative energy carrier is discussed; first, with the investigation of “hybrid” hydrogen storage systems that are meant to provide hydrogen for a fully fuel cell powered vehicle via a chemical reaction; and second, that of a thermally regenerative fuel cell system (TRFC) to partially supplant the energy needs of transport trucks by harnessing engine waste heat. Hybrid storage systems are comprised of a heterocyclic carrier that undergoes endothermic hydrogen release (indoline) and an organic hydride that undergoes exothermic release (amine boranes). Different embodiments are considered, varying in the mechanism of exothermic release (thermolysis vs. hydrolysis) and the mode of combination (physical vs. chemical). A thorough investigation into the effect of catalyst, sterics and temperature on the heterogeneously catalyzed dehydrogenation rate of N-heterocycles was executed. A number of trends with respect to the catalyst identity and the level of steric protection around the nitrogen atom were observed. The study towards a TRFC involved an investigation of the heterogeneous hydrogenation of benzylic ketones. Screening of a myriad of different catalysts was performed, including those with various supports, metals and modifications, and the examination of how both the sterics and electronics of the ketone affect the hydrogenation rate. A rapid hydrogenation at relatively low metal loadings and hydrogen pressures with extreme selectivity (>99.9%) is required. To date, however, such a combination has been elusive. The best selectivity was obtained with commercial Pd/SiO2 (99.99%), yet at a low conversion of 6%, after 1 h under 1 atm of H2 at 100 ˚C. In addition to the poor conversion, SiO2 is not electronically conductive and is therefore not fit for this application. The best viable catalyst, then, was a Pd/Vulcan XC-72 (carbon) catalyst made by the author with an observed 14% conversion and 98% selectivity under the same conditions. However, trends in activity and selectivity with respect to the catalyst and ketone have been characterized herein. / Thesis (Ph.D, Chemistry) -- Queen's University, 2012-05-23 13:37:53.172

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<p>In this work a modified polyol method was developed to synthesize in-house catalysts. The method was modified for maximum delivery of product and proved to be quick and efficient as well as cost effective. The series of IH catalysts were characterized using techniques such as UV-vis and FT-IR spectroscopy, TEM, XRD, ICP and CV.</p>

A series of 88 novel tetrahydroisoquinoline (TIQ) compounds have been synthesised for applications in asymmetric catalysis. Several chiral TIQ ligands, possessing N,O and N,N donor atoms, have been prepared and evaluated for the catalytic asymmetric transfer hydrogenation (ATH) of pro-chiral ketones. The highest selectivity obtained for the asymmetric transfer hydrogenation of acetophenone with the N,O donor atom ligands was >99 % ee at low temperatures in iso-propanol with [Ru(p-cymene)Cl2]2 as a pre-catalyst. The observed enantioselectivity was supported by theoretical calculations using the Jaguar interphase program (Paper I). An enantioselectivity of 70 % was obtained with the ligands possessing the N,N donor atoms with the observation that water played a significant role in the enantioselectivity of the ATH reaction of acetophenone (Paper II). An investigation into the usefulness of the TIQ scaffold with other donor atoms was also undertaken. A series of novel P,N oxazoline ligands were synthesised and coordinated to Iridium BArF. These complexes were screened as chiral catalysts for the high pressure asymmetric hydrogenation of unsymmetrical olefins. The reactions proceeded readily at ambient temperature and provided selectivities of up to >91 % ee with excellent conversion rates (>99 %) for the benchmark reactions. Based upon these favorable results, the ligands providing the best results were further screened on a variety of functionalized and unfunctionalised olefins (Paper III). The success of the TIQ backbone in ATH reactions prompted an investigation into its applications in carbon-carbon (C-C) bond forming reactions. The Henry (nitroaldol) reaction is an important C-C bond forming reaction with the chiral oxazoline class of ligands being widely utilised. A series of novel, chiral TIQ oxazoline ligands were synthesised and complexed to various metals (Cu, Sc, Co, Zn, Ni and Mn). These complexes were screened as chiral catalysts in the asymmetric Henry reaction. The highest enantioselectivity (>77 %) was obtained when Cu(OAc)2was employed as a pre-catalyst and iso-propanol as a solvent (Paper IV). The final chapter deals with carbon-sulphur bond formations facilitated by the conjugate addition of thioglycolate to various chalcones. A series of novel, chiral TIQ N-oxide ligands were synthesised and complexed to lanthanum. The complexes were screened for activity against the benchmark reaction and an enantioselectivity of 81 % was obtained. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2010.

No abstract available. / Thesis (Ph.D.)-University of Natal, Durban, 1973.

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