Syntheses and reactivity studies of phosphaalkynes and low oxidation state p-block heterocycles

The research described within this thesis revolves around two central themes, the reactivity of phosphaalkynes towards various substrates, and the synthesis and further studies of novel low valent group 13 and group 14 element complexes. The first chapter provides a general introduction to important concepts and molecules pertinent to the studies discussed herein, and provides a brief overview into the history of phosphaalkynes. Chapter 2 describes the synthesis of a series of 3H-1,2,3,4-triazaphospholes via a regiospecific pathway between phosphaalkynes and organic azides. Such [2+4] cycloadditions have shown marked similarities to Sharpless’s alkyne-azide click reactions, and had prompted interest in exploring them as high yielding routes in accessing new multidentate N/P ligands. Chapter 3 concentrates on coupling reactions between phosphaalkynes and amidinato stabilised group 14 element(I) dimers, as there were no examples of such reactions in the literature at the outset of this study. These reactions have typically yielded unusual systems, and some preliminary theoretical studies and experimental work has gone into understanding the electronic nature of these products. The research for Chapter 4 concerns itself with the use of sterically encumbering beta-diketiminato ligands in accessing new low valent gallium and group 14 element N-heterocycles. Finally, Chapter 5 looks at the reversible hydrogermylation of tert-butyl phosphaalkyne, tBuC≡P, by a beta-diketiminato stabilised germanium(II) hydride to give a novel C-germaphosphaalkene regioselectively.