HYBRID MULTIDENTATE PHOSPHINE-ALKENE LIGANDS FOR TRANSITION METAL COORDINATION CHEMISTRY AND CATALYSIS

The development of a new class of phosphine-alkene and thio-phosphine-alkene ligands based on a chalcone ferrocene framework, represents the primary focus of this study. The synthesis and characterisation of novel ligands, ferrochalcone 32 and thio-ferrochalcone 33, are described. The related alkene-phosphine ligands, the Lei ligand 17 and novel thio-Lei ligand 46, are further detailed. The coordination chemistry of four ligands (17, 32, 33 and 46) with various transition metals (Pt, Pd, Cu, Rh and Au) has been investigated in a comprehensive spectroscopis study. Single crystal X-ray analysis has been conducted at suitable junctures within the project. A surprising finding was that some solution-state structures were found to be different when studied in the solid state. The AuI complexes-containing the ligands have been successfully used in 1,5-enyne cycloisomerisation reactions. In addition to the coordination chemistry of the novel ligand systems, some interesting findings emerged For example, AuI complex of Lei ligand 17 and monodbaPHOS 74 undergoes an interesting solid-state [2+2] intramolecular cycloaddition transformation, giving cycloadduct, 72 and 77. An interesting finding includes the presence of impurity in commercially available Pd(OAc)2. Cyclopalladation of papaverine was carried out using pure and impure Pd(OAc)2, which resulted in the identification of novel Pd-dimer complex, 86. The result suggest that nitrite contaminants derive from impurities in Pd(OAc)2, and not from the oxidation of acetonitrile mediated by metallic Pd0, explain the formation of PdII-nitrito cyclopalladated products. Photocrystallographic metastable linkage isomerisation and complete conversion to an oxygen-bound nitrito complex 90 was also observed.