Synthesis and Reactivity of Anionic Low Valent and Hydrido Main Group Complexes supported by the NON-ligand

<p dir="ltr">The work detailed in this thesis describes the synthesis and reactivity of anionic low valent and hydrido main group complexes supported by the NON- and NNO-ligands ([NON]²- = [O(SiMe₂NDipp)₂]²-, Dipp = 2,6-<i>i</i>Pr₂-C₆H₃; [NNO]²- = [N(Dipp)SiMe₂N(Dipp)SiMe₂O]²-), with particular interest in systems featuring earth abundant and environmentally benign metal centres Al, Ga, Mg and Ca.</p><p dir="ltr"><i>Chapter one</i> provides a comprehensive literature review on anionic low valent and hydrido main group complexes. Within the p-block domain, low valent aluminyl anions are a relatively new class of compound featuring a nucleophilic Al(I) centre and charge-balanced by an alkali metal cation. Several modes of reactivity have been identified, including salt metathesis, oxidative addition, cycloaddition, and oxidation reactions. A simultaneous resurgence in reports on the reactivity of analogous anionic gallyl species is also discussed. Comparisons are drawn to s-block systems featuring anionic low valent and hydrido Ae complexes, charge-balanced by an alkali metal cation.</p><p dir="ltr"><i>Chapter two</i> investigates the reactivity of group 13 anions with a variety of ketones and aldehydes. A simple sequential addition protocol was developed for the selective synthesis of unsymmetrical (hetero-coupled) pinacol products by the potassium aluminyl. Isolation of an aluminium ketyl complex provides evidence for the accessibility of radical species. Product cleavage from the aluminium centre was achieved forming the disilylated 1,2-diol and a neutral aluminium iodide. Addition of acetophenone to the potassium gallyl afforded a potassium (alken-1-olate)(hydrido)gallate product which could react with a second equivalent of acetophenone to yield a 1,3-diphenylbutane-1,3-diolate ligand.</p><p dir="ltr"><i>Chapter three</i> examines the functionalisation of ethene via an aluminacyclopropane. The ‘activated’ C-C bond in the AlC2 metallacycle reacts with unsaturated substrates to afford ring-expanded products. Thermally induced 1,3-silyl retro-Brook rearrangement of the NON-ligand afforded the [NNO]²⁻ ligand ([NNO]²^- = [N(Dipp)SiMe₂N(Dipp)SiMe₂O]^2-). The mechanism of transformation was examined by density functional theory (DFT).</p><p dir="ltr"><i>Chapter four</i> discusses the synthesis of neutral alkaline earth metal (Ae) (Ae = Mg, Ca, Sr, Ba) complexes supported by the NON-ligand backbone and the attempted reduction of these compounds to form the corresponding anionic low valent species. Reduction of [Mg(NON)]₂ affords Mg(I) species containing NON- and NNO-ligands. Extraction with THF affords [K(THF)₂]₂[(NNO)Mg–Mg(NNO)] with a structurally characterised Mg–Mg bond. Reduction of [Ca(NON)]₂ afforded a reduced dinitrogen species, albeit in low yield.</p><p dir="ltr"><i>Chapter five</i> describes the synthesis, and structure of a series of anionic magnesium hydrides. A σ-bond metathesis reaction between the NNO-ligated alkali metal magnesiate precursor and phenylsilane yielded the corresponding hydride product. In contrast, the analogous reaction with NON-ligated alkali metal magnesiates did not yield the corresponding hydride product.</p><p dir="ltr"><i>Chapter six</i> presents a concise summary of the experimental details pertinent to this thesis, both for synthetic manipulations of materials, and X-ray crystallographic processing and analysis of samples.</p>