This thesis is concerned with the synthesis and chemistry of series of zwitterionic magnesium complexes, with the aim of providing the first evidence of zwitterionic potential magnesium polymerisation catalysts. The positive charge on the magnesium centre can be stabilised by preparing zwitterionic species incorporating existing and specially developed chelating nitrogen donor ligands. Chapter One serves as general introduction about ethylene polymerisation throughout the periodic table, and the polymerisation activity of magnesium complexes supported by bidentate nitrogen donor ligands. Chapter Two describes the synthesis of a series of magnesium complexes using [K(H<sub>2</sub>B (pz)}<sub>2</sub>] ligand. Predominantly [{H<sub>2</sub>B(py)}<sub>2</sub>Mg(THF)n] (n: 1 or 2) bischelate complexes are obtained in order to satisfy the electronic requirement of magnesium. The charge transfer from the ligand has the effect of neutralising the formal Mg<sup>2+</sup> charges, and this does not produce zwitterionic complexes. Schlenk equilibrium suggests a solvation and association, by which MgCl<sup>2</sup> is formed, and associations by u-bridging halide predominate. Chapter Three describes the synthesis of three different borate-centred ligands suggested for zwitterionic magnesium complexes. Chapter Four explores the chemistry of boron supported by the B-diketiminate ligand. Complexation of B-diketiminate ligand with boron results in the formation of several reaction products, via radical processes and provides the first evidence of borane carbine analogue, [HC(MeCNAr’)<sub>2</sub>B] (Ar’: 2,6-diisopropylphenyl). Chapter Five describes the synthesis of a series of magnesium complexes using [R<sub>2</sub>AFA(H)] (R:Cy, AFA; 6-aminofulvene-2-aldimine) ligands. Co-ordination of the Cyclopentadienyl (n<sup>5</sup>-Cp) portion of the ligand results in complexes of zwitterionic character in which a positive charge residues on the magnesium. Schlenk equilibrium suggests a salvation and association, by which MgCl<sub>2</sub> is formed to provide complexes [(R<sub>2</sub>AFA)Mg(Cl)Et<sub>2</sub>O] and [[(R<sub>2</sub>AFA)<sub>2</sub>Mg]. Ethylene polymerisation studies of [(R<sub>2</sub>AFA)MgME] were implemented and revealed that the compound is inactive under both mild and forcing conditions. Chapter Six explores the technique of high-resolution X-ray diffraction in the complex of [Mg{(pz)<sub>2</sub>BH}<sub>2</sub>].
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:654036 |
| Date | January 2004 |
| Creators | Lorono Gonzalez, Daniel Jose |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/12464 |
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