Abstract
This thesis details research into several of aspects of organoruthenium complexes which function as homogeneous catalysts for regioselective hydrogen isotope exchange. The first chapter includes a review of previous investigations into homogeneous transition metal catalysis in this area. Some examples of applications within the pharmaceutical sciences are also used to illustrate the need for developing new catalysts in this area, with the accent on their regioselective action, as well as improved efficiency. In the second chapter, the synthesis and characterisation of the various catalysts is described. Many of the complexes have been obtained by procedures which differ from those previously reported. A brief discussion on the usefulness of the ruthenium-blue cluster-anion is also given. Details of X-ray crystallographic studies that were performed on the ruthenium catalysts are described in the next chapter. The parent catalyst, Ru(acac)3, was shown to exist in two different forms (one monoclinic, the other orthorhombic) and an early literature report relating to its crystal structure corrected. The substituted acetylacetonate catalysts Ru(3Cl-acac)3, Ru(3Br-acac)3 and Ru(3NO2-acac)3 are the first tris(3-substituted β-diketonato) complexes of any metal to be characterised crystallographically. Crystallographic evidence of catalyst reduction and solvation is also presented; a highly unusual ruthenium(I) complex, formulated as [Ru(PhCO2)(PPh3)2(HTO)2], was isolated when RuCl2(PPh3)3 was tested as a catalyst for the regioselective tritiation reaction. This provides valuable and indisputable evidence for use when considering reaction mechanisms of this kind. The final chapter is concerned with kinetic investigations using the ruthenium catalysts which have been prepared, and also details studies on the labelling of various acids using tris(acetylacetonato)ruthenium(III). The results show that the catalyst appears to be sensitive to the presence of nitrogen in the substrate, and also steric hindrance, which by itself, provides further useful deductions upon which to draw in proposing a new reaction mechanism.