| Samenvatting: | <p>This Thesis describes the synthesis and characterisation of new Group 2, Group 3 and lanthanide amide, alkyl, halide, borohydride and alkoxide complexes, and their uses as catalysts for the living ROP and immortal ring-opening polymerisation (<em>i</em>ROP) of <em>rac</em>-, <em>L</em>, <em>D</em>- and <em>meso</em>-lactide.</p> <p><strong>Chapter One</strong> introduces cyclic esters and possible mechanistic pathways leading to polyesters by ROP. Living and immortal ROP, including their kinetic characteristics are discussed. An overview of ROP from an industrial perspective and a literature review are also given.</p> <p><strong>Chapter Two</strong> describes the synthesis and characterisation of a new series of magnesium and zinc amide, alkyl, halide, borohydride and alkoxide complexes supported by a carbazole-bis(dimethyloxazoline) ligand. Their activities towards the ROP of <em>rac</em>-, <em>L</em>- and <em>meso</em>-lactide are presented. Detailed mechanistic studies using spectroscopic techniques are discussed and a new mechanism is proposed.</p> <p><strong>Chapter Three</strong> describes the synthesis and characterisation of a new series of calcium, strontium, yttrium, lanthanum and samarium amide, alkyl, halide, borohydride and alkoxide complexes supported by a carbazole-bis(dimethyloxazoline) ligand. Their activities towards the ROP of <em>rac</em>-, <em>L</em>- and <em>meso</em>-lactide are presented. Detailed mechanistic studies using spectroscopic techniques are discussed.</p> <p><strong>Chapter Four</strong> describes the synthesis and characterisation of a new series of magnesium, calcium, strontium, yttrium, lanthanum and samarium amide, halide and borohydride complexes supported by a chiral carbazole-bis(isopropyloxazoline) ligand. Their activities towards the ROP of <em>rac</em>-, <em>L</em>-, <em>D</em>- and <em>meso</em>-lactide are presented.</p> <p><strong>Chapter Five</strong> contains experimental details and characterising data for the new complexes reported in this Thesis.</p> <p><strong>CD Appendix</strong> contains .CIF files for all the new crystallographically-characterised complexes.</p>
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