In this study several systems have been examined: in particular, asymmetric hydrogenation of C=C bonds and a prototypical C-C bond forming reaction. By synthesis and application of a range of chiral pyrrolidine-based sulfides, which robustly anchor to Pd nanoparticles, true heterogeneous enantioselective catalytic C=C hydrogenation has been accomplished. The behaviour and adsorption geometry of the reactant on a Pd(111) single crystal has been studied using a range of surface science techniques, allowing elucidation of the likely reaction mechanism. Investigation of four structurally related organic substrates and correlation of their reactive behaviour with the respective molecular adsorption geometries and molecular structures led to a reaction model being proposed, which correctly predicts the enantiomer observed experimentally in excess. Sonogashira coupling is one of a substantial class of C-C bond forming reactions, which are ubiquitous in synthetic organic chemistry. Despite the advantages of using heterogeneously catalyzed routes to perform such manipulations, mechanistic aspects of solid catalysts applied to such systems, especially the nature of the active species, remain both controversial and poorly understood. Reactor studies of the gold nanoparticle catalysed reaction in combination with pre- and post-reaction characterisation techniques have shown the identity of the active catalyst to be metallic Au<sup>0</sup> nanoparticles. Observed particle size effects on catalysis were also seen to correlate well with the behaviour of the reactants on a Au(111) single crystal surface <i>in vacuo. </i>The selectivity enhancing effect of rare earth oxide supports has also been investigated. Overall, the insights provided by combining conventional surface science techniques with catalytic data from reactions carried out, under conditions pertinent to practical solid-liquid catalysis, pave the way for the rational design of future catalysts.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:596504 |
| Date | January 2011 |
| Creators | Beaumont, S. K. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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