New nitrogen-phosphorus ligand frameworks based on cyclodiphosph(III)azanes

• Main Author: Doyle, Emma Louise
• Published: University of Cambridge 2004
• Subjects: 546
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598634

In Chapter 1, an account of the current research that has been carried out in the area of phosphorus-nitrogen systems with particular emphasis on cyclodiphosph(III)azanes is presented. The discussion considers the synthetic and structural differences between these compounds and focuses on their coordination chemistry. The major types of cyclic phosph(III)azanes are discussed along with the effect of the R group substituent and the synthetic procedure employed upon their structural type. Chapter 3, concerns the synthesis of new dichlorocyclodiphosph(III)azane species, [CIP(m-NR)]₂, and relates the synthetic and structural details of these to previously structurally characterised dichlorocyclodiphosph(II)azanes. These compounds are of particular interest because of their usefulness as precursor compounds to symmetrically heterosubstituted cyclodiphosph(III)azanes, and especially to macrocycles. Chapter 4 concerns the investigation of various substitution reactions that were undertaken with chloro-substituted cyclodiphosph(III)azanes, with the aim of producing amino-substituted species. It then turns to the reactions of these species with organo alkali metal reagents, such as ⁿBuLi, to obtain the anion derivatives. An interesting discovery is the existence of complexes containing sterically-uncongested [(RN)₂P]^- monoanions stabilised by coordination. The work presented in Chapter 5 discusses studies on the formation of macrocycles and gives insight into the mechanistic pathways to these species. This chapter initially addresses the formation of tetrameric and pentameric macrocycles constructed from [{P(m-N^tBu)}₂NH] units and pinpoints a divergent mechanism in their formation. This work leads to a proposed ‘twist’ mechanism that provides an understanding of steric factors governing the formation of different types of cyclodiphoph(III)azanes and the size of the macrocycles produced. In total, seventeen new compounds are described in this thesis, all of which have been structurally characterised.