Polycyclic and Oligocyclic Phosphorus-Nitrogen Ring Systems

This thesis is concerned with the study of the design, synthesis and reactivity of phosphorus-containing oligocyclic ring systems, comprising bidentate, polycyclic phosphorinanones. The initial step was to establish a synthetic route for a series of bisamides, containing either NH, NH or NH, OH groups with bridging units. The reaction of these bisamides with phosphorus trichloride afforded the desired bis- chlorophosphine, bis-PCl derivatives. By the reaction of the bis-PCl species with trimethylsilyl-substituted amines, a series of polycyclic, potentially bidentate PN compounds was formed in high yield. The oxidative addition of hexafluoroacetone (HFA) and tetrachloroorthobenzoquinone (TOB) to the bis-P(III) compounds thus obtained was investigated, and a series of compounds of five-coordinate phosphorus was isolated. In the reaction of the bis-P(III) compounds with Pt[COD]Cl2 (COD = cycloocta-1,5-diene) and [NBD]Mo(CO)4 (NBD = norbornadiene) new inorganic ring systems were formed in which two phosphorus atoms are chelating the metal centres (Pt(II) and Mo(0)). Crown ether-like phosphorus-containing polycyclic compounds were obtained from the reaction of the bis-PCl compounds with a series of bistrimethylsilylethers, the process involving condensation of two active components but not requiring high-dilution techniques. All the products were obtained in moderate to high yield. They were more stable than the acyclic compounds and did not undergo isomerisation reactions in solution. The polycyclic compounds of variable ring-size were found to differ significantly in their chemical reactivity, as well as in their physical properties. Oxidation of the polycyclic compounds with (NH2)2C(:O)∙H2O2 and elemental sulfur lead to the P(:O) and P(:S) derivatives, respectively. All the oxidized polycylic compounds were obtained in high yield, and no decomposition reactions were observed, indicating the high stability of the ring systems.