Late transition metal complexes of bulky mono- and bi-nucleating ligands : synthesis and catalytic applications
In Chapter One, a background to the application of binucleating ligands in biomimetic chemistry sets the scene for a comprehensive discussion of homogeneous catalysis in the field. Chapter Two describes the strategies employed for the preparation of sterically encumbered multidentate oligopyridylimine ligands. In Chapters Three and Four, the new oligopyidylimine ligands prepared in Chapter Two are treated with divalent metal halides (iron, cobalt, nickel, zinc) and the resultant complexes fully characterised. Specifically, Chapter Three focuses on the reactivity of the potentially pentadentate ligands [bis(imino)terpyridine and imino-quaterpyridine] while Chapter Four concentrates on the resulting coordination chemistry of the potential tetra-, hexa- and hepta-dentate ligands [imino-terpyridine, bis(imino)quaterpyridine and bis(imino)quinquepyridine]. In both chapters, theoretical calculations (DFT) on pre-identified complexes are used in order to investigate the effect of the R substituent (H vs. Me) and metal centre on the coordination chemistry of the ligand. To conclude the synthetic work, the screening for polymerisation or oligomerisation of ethylene is systematically investigated with a selection of the new complexes. In Chapter Five, the synthesis of multidentate ligands featuring sterically encumbered imino-pyridine end-groups linked by phenyl-, thiophene- and phenolate-spacers is studied. The new (pro)ligands are fully characterised and their coordination chemistry with the same series of divalent metal halides is investigated. Furthermore, derivatisation of pre-identified bimetallic complexes is performed. Finally, a selection of the bimetallic compounds is screened as precatalysts for the oligomerisation and/or polymerisation of ethylene.