This thesis is concerned with the synthesis and chemistry of series of zwitterionic magnesium complexes, with the aim of providing the first evidence of zwitterionic potential magnesium polymerisation catalysts. The positive charge on the magnesium centre can be stabilised by preparing zwitterionic species incorporating existing and specially developed chelating nitrogen donor ligands. Chapter One serves as general introduction about ethylene polymerisation throughout the periodic table, and the polymerisation activity of magnesium complexes supported by bidentate nitrogen donor ligands. Chapter Two describes the synthesis of a series of magnesium complexes using [K(H₂B (pz)}₂] ligand. Predominantly [{H₂B(py)}₂Mg(THF)n] (n: 1 or 2) bischelate complexes are obtained in order to satisfy the electronic requirement of magnesium. The charge transfer from the ligand has the effect of neutralising the formal Mg²⁺ charges, and this does not produce zwitterionic complexes. Schlenk equilibrium suggests a solvation and association, by which MgCl² is formed, and associations by u-bridging halide predominate. Chapter Three describes the synthesis of three different borate-centred ligands suggested for zwitterionic magnesium complexes. Chapter Four explores the chemistry of boron supported by the B-diketiminate ligand. Complexation of B-diketiminate ligand with boron results in the formation of several reaction products, via radical processes and provides the first evidence of borane carbine analogue, [HC(MeCNAr’)₂B] (Ar’: 2,6-diisopropylphenyl). Chapter Five describes the synthesis of a series of magnesium complexes using [R₂AFA(H)] (R:Cy, AFA; 6-aminofulvene-2-aldimine) ligands. Co-ordination of the Cyclopentadienyl (n⁵-Cp) portion of the ligand results in complexes of zwitterionic character in which a positive charge residues on the magnesium. Schlenk equilibrium suggests a salvation and association, by which MgCl₂ is formed to provide complexes [(R₂AFA)Mg(Cl)Et₂O] and [[(R₂AFA)₂Mg]. Ethylene polymerisation studies of [(R₂AFA)MgME] were implemented and revealed that the compound is inactive under both mild and forcing conditions. Chapter Six explores the technique of high-resolution X-ray diffraction in the complex of [Mg{(pz)₂BH}₂].

Pulsed laser photolysis-probe techniques have been used to investigate the nascent internal state distributions of OH(X<SUP>2</SUP>Π) produced in reactions of the type: O(<SUP>3</SUP>P) + RH → OH(X<SUP>2</SUP>Π) + R RH is a saturated hydrocarbon, which is chosen to contain representative primary, secondary or tertiary C-H bonds. Reactive superthermal O(<SUP>3</SUP>P) atoms are generated by photolysis of NO<SUB>2</SUB> at either 337, 308 or 248 nm. By changing the wavelength of photolysis of NO<SUB>2</SUB>, the collision energy of the reaction can be effectively altered. The OH product is detected in a state-specific manner by laser-induced fluorescence (LIF) on the A<SUP>2</SUP>Σ<SUP>+</SUP> ←X<SUP>2</SUP>Π transition. The delay between the photolysis and probe pulses is kept short enough to allow the partitioning of the available energy amongst the possible vibrational, rotational and fine-structure states to be determined from collisionally unmodified OH LIF spectra. The OH product, from the reaction between O(<SUP>3</SUP>P) and RH, is found to be rotationally cold. It is also apparent that the rotational distribution is largely independent of the nature of the R group. These findings have been interpreted as evidence that the reaction exhibits a strong preference for collinear approach of the O(<SUP>3</SUP>P) atom to the C-H bond from which the H atom is abstracted. In contrast, the degree of vibrational excitation depends strongly on both the type of C-H bond and the collision energy. These observations are consistent with the shift towards an "earlier" reaction barrier with increasing reaction exothermicity, which occurs as the H atom being abstracted is changed from primary to secondary to tertiary. The OH spin-orbit state distribution is non-statistical. The correlations between the spin-orbit states of the O(<SUP>3</SUP>P) reactant and OH product have been clarified. A purely adiabatic correlation does not correctly predict the observed product spin-orbit state distribution but a model, which includes non-adiabatic coupling of surfaces with the same projection of total electronic angular momentum, gives much improved agreement. This model has interesting but yet unstudied corollaries for the differential reactivity of the O(<SUP>3</SUP>P<SUB>j</SUB>) states.

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No description available.

The work described in this thesis involves the use of several techniques to investigate cyclopentene, cyclopentane and methylcyclopentane adsorption on metal surfaces. <SUP>2</SUP>D NMR spectroscopy was used to study the products of the exchange reaction of methylcyclopentane with deuterium over supported metal catalysts. The distribution and extent of exchange of deuterium in the hydrocarbon was found to vary with the metal used. <SUP>2</SUP>D NMR spectroscopy was used in conjunction with mass spectrometry to elucidate information on the intermediate species involved. Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and transmission infrared spectroscopy were employed to follow adsorption of cyclopentene, cyclopentane and methylcyclopentane on EuroPt-1 <i>in situ</i>. The behaviour observed using infrared spectroscopy was correlated with behaviour in the gas phase observed using mass spectrometry and thermal conductivity in the flow system used. This allowed quantification and analysis of the reactants and products. Molecular adsorption of the three molecules was observed, and temperature programmed desorption (TPD) was used to follow behaviour with increasing temperature. This allowed activation energy to desorption to be estimated. Cyclopentene showed complicated behaviour on heating, forming an unsaturated species on the surface. Cyclopentane and methylcyclopentane desorbed molecularly into the gas phase. Reflection Absorption Infrared Spectroscopy (RAIRS) was used to follow adsorption and TPD of the same hydrocarbon molecules onn a Pt(111) single crystal under UHV conditions. Adsorption was observed at low temperature, and multilayer build up of the three hydrocarbons was observed on increasing exposure.

The last twenty years have witnessed a great increase in the discovery and development of chiral reagents for application in asymmetric synthesis. The aim of this project was to develop a novel series of chiral ligands from inexpensive materials, and to assess their potential as chiral catalysts in asymmetric synthesis. This was to be achieved through the exploitation of the chirality of the biphenanthryl system. A pre-existing route into such asymmetrically substituted biphenanthryl systems was optimised to give racemic quantities of 10'-hydroxy-9,9'-biphenanthryl-10-carboxyaldehyde. Resolution of this racemate was achieved through the formation of a diastereoisomeric hydrazone with S-AMP. Chirally pure 10'-hydroxy-9,9'-biphenanthryl-10-carboxaldehyde was used as the starting point for the generation of a series of chiral catalysis. Four bi-dentate biphenanthryl ligands were developed and applied in asymmetric synthesis. A chiral hydrazone, oxime and <i>tert</i>-amine were applied in the asymmetric addition of diethylzinc to aldehydes. A primary amine was synthesised and applied in the enantioselective borane reduction of pro-chiral ketones. Chiral GC analysis of the modified substrates from these reactions was carried out by Avecia. Finally, attempts were made to modify the chiral biphenanthryl moiety towards the synthesis of a chiral dihydropyridine reagent. This system was hoped to mimic the co-enzyme NADH.

The chemistry of butane has been studied over two well characterised catalysts, EuroPt-1 doped with potassium hydroxide to 1% weight in potassium. The exchange of butane with deuterium produced a U shaped distribution of deuterated products, with maxima at the singly exchanged and fully exchanged butanes over both catalysts. The rate of exchange over the 1% potassium doped catalyst was nearly two orders of magnitude lower than over EuroPt-1. The application of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) to strongly infrared absorbing catalytic systems was discussed, with the inherent advantages and disadvantages of the technique. It was concluded that it was a useful method for studying the region of the infrared spectrum associated with carbon-hydrogen stretching vibrations, but the strong absorbance of the catalysts' silica support made study of the carbon-hydrogen deformation region difficult for both EuroPt-1 catalysts. The adsorption of butane on EuroPt-1 and 1% potassium doped EuroPt-1 in a flow system was studied using DRIFTS at 298 K and 378 K. The chemistry was similar over the two catalysts, but all infrared intensities were signficantly lower over the 1% potassium doped catalyst. In comparison with equivalent single crystal studies, the main species present at 298 K was assigned to a di-σ or di-σ/π adsorbed butane. Heating preadsorbed butane to 378 K, or adsorbing butane at 378 K produced an infrared spectrum assigned to butylidyne. Further heating evolved hydrocarbon as methane. The reaction of the adsorbed species with pulses of hydrogen was also studied.

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The chemical and physical effects of potassium promotion on prepared nickel-alumina catalysts have been examined using "<I>in-situ</I>" Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Temperature Programmed studies and X-ray Powder Diffraction (XRPD). Various preparative methods were explored to obtain catalyst samples with a high metallic surface area. A sequential precipitation technique was employed, yielding a highly loaded nickel alumina catalyst (56 %wt Ni) with the hydrotalcite structure, typical of other industrial catalysts. Subsequent potassium promotion of this initial catalyst was achieved by impregnation. X.R.P.D. studies showed no observable changes in the bulk structure of the catalyst at room temperature or during calcination with low loadings of potassium (≤ 1 %wt). However, at higher loadings, potassium carbonate/oxide peaks became apparent but there was no indication of any other potassium derivatives. The presence of potassium both inhibited the reduction of the catalyst and brought about a reduction of the nickel surface area in the final reduced catalyst. Infrared studies showed definite changes in the surface chemistry of the catalyst with potassium promotion. Adsorption of carbon monoxide showed a downward shift in the wavenumber of the characteristic bands together with an apparent change in the relative proportions of the different carbon monoxide adsorbed species. Temperature dependent adsorption studies further indicated the formation of an activated species which was increasingly stable as a function of potassium promotion. The same species was observed in analogous carbon dioxide experiments. The effect of potassium on the infrared spectra from adsorbed ethene, propene and but-1-ene was more subtle.

No description available.