Lipton, Catherine Elizabeth; (2003) Studies on caged nitrogen compounds. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis describes studies on caged nitrogen compounds, in particular hexamethylenetetramine. Thus, Chapter One presents an introduction to the synthesis and chemistry of hexamethylenetetramine. Chapter Two describes efforts to synthesise new caged nitrogen compounds using the synthesis of hexamethylenetetramine as a model. First, studies of the reaction of formaldehyde and ammonia in the presence of a number of metal amine complexes are described. Secondly, investigations into the use of some macrocyclic metal amine complexes as precursors to high energy compounds are reported. In Chapter Three it has been shown that hexamethylenetetramine acts as a ligand on organometallic compounds of ruthenium and rhodium. The ligand can bind in a monodentate fashion, as in [Ru(η3:η3-C10H16)Cl(hmt)] or [Ru(η6-p-cymene)Cl2(hmt)]; the latter has been characterised using X-ray crystallography. Binuclear complexes have also been prepared, with hexamethylenetetramine bound terminally, as in the chloride bridged salt [(η6-C6H6)ClRu(μ-Cl)2Ru(η6-C6H6)(hmt)]Cl, or bound as a bridging ligand, as in [{Rh(η5-C5Me5)Cl}2(μ-hmt)]. Chapter Four presents reactions of hexamethylenetetramine with bis(benzonitrile)palladium(II)dichloride to produce [Pd(hmt)2Cl2] and [Pd(hmt)2Cl2]n. The complex [Pd(hmt)2Cl2] has been shown by X-ray crystallography to exist as the trans isomer in the solid state. The reaction of chloro(2-methyl-η3-allyl)palladium(II) with hexamethylenetetramine gave [PdCl(η3-C4H7)(C6H12N4)] and [Pd2Cl2(η3-C4H7)2(μ-C6H12N4)], both of which have been characterised using X-ray crystallography and low temperature 1H NMR spectroscopy. Variable temperature 1H NMR studies and computer simulation of spectra have given an insight into the solution dynamics of these compounds. Low temperature 1H NMR studies have established the existence of [Pd4Cl4(η3-C4H7)4(μ4-C6H12N4)], where hexamethylenetetramine acts as a tetradentate ligand. Chapter Five reports the synthesis of [Rh2(O2CCH2CH3)4(hmt)2] and [Rh2(O2CCH2CH3)4(hmt)]n. The redox properties of both complexes have been investigated using cyclic voltammetry. Using these electrochemical results, the donor ability of a number of ligands has been determined as hmt>[PdCl(η3-C4H7)(hmt)]>[Rh2(O2CCH2CH3)4(hmt)]. A simple rationale for this ordering has been suggested.

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