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Among the classes of organic transformations, cycloaddition reactions constitute a powerful and versatile strategy for the rapid assembly of complex polycyclic scaffolds in a highly stereos elective fashion. A unique feature of this class of reactions resides in the possibility to alter the geometry and coordination number of the metal centre in order to increase the reactivity and selectivity of the process. Hence, the development of this strategy highlighted the opportunity to synthesize complex molecular architectures in a highly convergent and stereos elective manner using mild operating conditions, thereby improving the efficiency with respect to atom-economy and environmentally benign synthesis. Among the metal-catalysed carbocyclisation reactions, the Pauson-Khand (PK) methodology enables the straightforward construction of cyclopentenone derivatives from readily available synthons. Distinguishing feature of this reaction is the incorporation of a carbon monoxide unit into a polycyclic framework with the production of carbonyl systems that are amenable of further functionalisation. In this context, we performed a detailed computational analysis of the mechanism of the Rh-catalysed diastereoselective PK reaction. This study outlined the possibility to enhance the reactivity of 1,6-enynes towards the carbocyclisation through the incorporation of electron-withdrawing substituents on the alkyne terminus. Further experimental analysis revealed that the employment of a chlorine substituent on the alkyne moiety exerted a beneficial effect on the reactivity of 1,6-enynes and thereby provided a novel highly diastereoselective Rh-catalysed PK reaction at room temperature. The enhanced reactivity of chlorinated 1,6-enynes was subsequently exploited in the Rh-catalysed asymmetric PK reaction. A detailed optimisation study revealed that the electronic and geometric properties of iv chiral bisphosphine ligands exerted a remarkable influence on the reactivity of 1,6- enynes towards the carbocyclisation process. Hence, the synergic combination of chlorinated 1,6-enynes and SEGPHOS-type bisphosphine ligands allowed a highly enantioselective rhodium-catalysed PK reaction of substrates that are generally unreactive, such as 1,6-enynes bearing substituents on the alkene position. Hence, methodology expanded the synthetic potential of the PK reaction and moreover, provided a highly enantioselective construction of bicyclopentenone scaffolds under extremely mild operating conditions.

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Deactivation of a 0.53 wt% Pt/γ-Al_2­O₃ catalyst due to strongly adsorbed carbonaceous residue was investigated.  The role of the carbonaceous residue formed during hydrocarbon conversion reactions of 1-octene, toluene and 1:1 volume mixture of 1-octene/toluene at 300, 400 and 450°C was established and a model developed to account for the activity and selectivity changes at the very start of the reaction, just as the hydrocarbon residue begins to form on the surface of the catalyst.  CO pulse chemisorption was used to determine the extent of Pt surface blocked by the hydrocarbon residue by titrating the Pt sites that remained exposed.  The efficiency of catalyst regeneration with H₂ at 400°C was investigated and hydrocarbon reactions were performed on the regenerated catalyst to assess the catalytic activity and selectivity on a Pt surface covered with carbonaceous residue.  Characterisation of the carbonaceous residue deposited on the catalyst during hydrocarbon conversion reactions was carried out using TPO, TGA-MS and Raman microspectroscopy.  The amount, composition, reactivity and chemical structure of the carbonaceous residue in relation to reaction time and temperature was investigated. Increasing the reaction temperature accelerated the formation of coke.  The H:C ratio of the carbonaceous residue played an important role in the selectivity of the hydrocarbon reaction.  In addition, two batches of the 0.53 wt% Pt/γ-Al₂O₃ catalyst spent six months in an industrial Pyrolysis gasoline (Pygas) Hydrotreatment reactor.  The catalyst batches were strategically placed at the inlet and outlet of the reactor.  Raman microspectroscopy revealed that the coke accumulated on the individually coked samples consisted of a mixture of disordered and ordered pre-graphitic polycrystalline coke.  The reactivity and type of the coke varied between the samples placed near the inlet or the outlet of the industrial reactor.

In order to correlate the properties of the catalyst to those of the support, activated carbons from various raw materials and activation methods were fully characterised in terms of their physical properties, surface chemistry and elemental composition. Significant differences were identified whereby the porosity of the carbon, and hence the surface area, varied with the raw material used whilst the surface chemistry depended on the method of activation. The interdependence of the carbon properties made it difficult to isolate particular carbon features which were responsible for the catalytic properties. As such, a wood carbon was subjected to a variety of oxidative and reductive treatments aimed at altering the surface chemistry whilst maintaining the pore structure. 5% platinum on carbon catalysts were prepared on each of the carbons using an excess solution impregnation of hexachloroplatinic acid under two sets of preparation conditions. Significant differences in metal dispersion and catalytic activity were identified and attributed to features of the carbon support, with both the pore structure and the surface chemistry playing significant roles. The prepared materials were used as catalysts for the selective hydrogenation of cinnamaldehyde. Selectivity and activity were shown to be affected by the support which could be attributed to both the physical and chemical nature of the carbon. As a result it may be possible to select a particular carbon support that would produce an active catalyst for a particular reaction.

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Recently, our research group has been developing novel reactions involving powerful tetraazaalkene-based donors, reducing aryl halides into their corresponding aryl radicals or aryl anions. This thesis reports the development of new powerful donor D, a novel donor structure prepared by a novel route from precursor A. Oxdation of D into diction E provided suitable material for X-ray crystal analysis and electrochemical measurements of the redox potential for the D/E couple. Comparison with other neutral organic electron donors prepared in our group or published by others showed that the bispyridinylidene-based donors presented in this thesis are the isolated organic reagents with the most negative redox potentials recorded to date.