CARCAS · Construction of Aqueous-soluble Ruthenium Catalysis for Asymmetric Synthesis

Final Activity Report Summary - CARCAS (Construction of Aqueous-soluble Ruthenium Catalysis for Asymmetric Synthesis)

The primary aim of this project is the rational planning and construction of organometallic compounds with unique bi-functional properties for the purposes of performing new types of catalytic activity (performing selective chemical reactions requiring less energy). In most cases, only the metal centre is the active site with the catalytic complex. However, design and synthesis of a new generation of ligand types offered a cooperative interaction with the metal centres and enables an unprecedented activation of small molecules which are of great importance to the field of chemistry. This includes the currently high relevant dihydrogen (H2) molecule, for which the complexes synthesised in this project perform high efficient catalytic cleavage and hydrogenate industrial important substrates such as styrene. This project differed from other studies of hydrogenation in that instead of optimising conditions such as temperature and pressure, the catalytic complexes themselves were strategically changed to directly understand the mechanism of action at a fundamental level. Using a wide variety of modern spectroscopic techniques (NMR) combined with advanced computational studies, a new hybrid form of H2 activation was discovered, along with features vital to the catalyst's operation. Building on new synthetic techniques, another family of complexes were designed and prepared to perform chloride abstraction and cyclisation of complicated heavily functionalized substrates. Although the complexes proved not as efficient as current compounds, these new species demonstrated unusual high selectivity never before observed. Furthermore these complexes are the first known to activate the reaction cycle without use of a radial promoter or reducing metal agent. Moreover, some of the complexes perform an unprecedented activation of dioxygen (O2) for which limited studies are known in the field of ruthenium. Using the latest in analytical and characterisation techniques combined with computational studies, a new pathway for O2 insertion was determined. Overall these discoveries shed new light about the interface between metals and bi-functional ligands and in particular the factors critical to controlling the strength of interaction. The knowledge gained from the experiments related to this project has built a strong foundation for the continuing research in the areas of hydrogen transfer and alcohol dehydrogenation, both are increasing vital topics in the context of creating sustainable chemical technology.

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