| Summary: | This thesis is mainly focused on the investigation of the chemistry and reactivity of the hypersilyl ligand {[(Me<sub>3</sub>Si)<sub>3</sub>Si]<sup>-</sup>}, and the rationalisation of the use of siloxanes as precursors ([(R<sub>2</sub>SiO)<sub>n</sub>]). A total of ten new compounds have been prepared from these studies, and X-ray crystallography forms a central basis of the analysis of these species, along with NMR spectroscopy and various other analytical techniques. The first novel compound described is [(Ph<sub>3</sub>Si)(Me<sub>3</sub>Si)<sub>2</sub>SiK<sup>.</sup>18-crown-6] (3). Despite isolating 3 in pure both crystalline and powder form the difficulty in synthesising the compound in large scale meant that its reactivity could not be investigated fully. A series of Si-M complexes was made in the form of [(Me<sub>3</sub>Si)<sub>3</sub>Si<sup>.</sup>MX<sub>3</sub>]<sup>-</sup>[K<sup>.</sup>18-crown-6]<sup>+ </sup>(4-6, M = Al or Ga, X = Cl or Br), as well as [(Ph<sub>3</sub>Si)(Me<sub>3</sub>Si)<sub>2</sub>Si<sup>.</sup>GaCl<sub>3</sub>]<sup>-</sup>[K<sup>.</sup>18-crown-6]<sup>+</sup> through the reaction of the respective silyl anion with the corresponding group 13 halides. Due to yield considerations, 6 was chosen as a precursor to study the thermal decomposition behaviour of this type of compounds. The reaction between (Me<sub>3</sub>Si)<sub>3</sub>SiK<sup>.</sup>18-crown-6 (1a) with (P<sub>4</sub>) led to the formation of the unusual {P<sub>8</sub>[(Me<sub>3</sub>Si)<sub>3</sub>Si]<sub>2</sub><sup>.</sup>K<sup>.</sup>18-crown-6}<sup>-</sup>[K<sup>.</sup>18-crown-6<sup>.</sup>(THF)<sub>2</sub>]<sup>+</sup> (8). The discovery of 8 allows an investigation into the relatively poorly understood mechanism for this type of reaction, and a proposed mechanism, supported by computational calculations, is discussed. The reaction between hypersilyl potassium (1a) and mesityl nitrile gave 6,8-dimethyl-1-amino-3-mesityl-isoquinoline. Finally, the unexpected formation of [2-PySi(Me)<sub>2</sub>LiO]<sub>6</sub> and {[18-crown-6<sup>.</sup>]GaCl<sub>4</sub>}<sub>∞</sub> are also described.
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