Main group chemistry, and chemical catalysis using main group elements, has undergone
a renaissance in the new millenium. Low-valent main group complexes have demonstrated
reactivity once thought possible only for the transition metals (TM), and the advent of ‘frustrated
Lewis pair’ (FLP) chemistry has enabled main group compounds to perform efficient catalysis,
most notably catalytic hydrogenation. This thesis describes advancements that have been made
by combining the TM-like nature of the low-valent group 14 elements with the concept of FLP
chemistry.
Chapter 1 provides an introduction to the history and study of catalysis, the structure, bonding and reactivity of low-valent group 14 compounds, and FLP chemistry.
Chapter 2 explores the FLP-type oxidative addition of H2 to a stannylene, catalysed by
Lewis bases. A comprehensive mechanistic understanding is developed from a host of experimental and computational techniques. The use of Sn(IV) hydrides as reducing agents is
subsequently investigated, and found to be limited in potential.
Chapter 3 investigates the scope of stannylenes and germylenes that can participate in the
FLP-mediated H2 activation reaction. A second mechanism is identified, generating transient
E(II) monohydrides which are found to be potent reductants for ketones.
Chapter 4 applies the understanding gained from the previous chapters to catalysis, uncovering the first example of catalytic hydrogenation of an imine using a tetrylene. Amidotetrylenes
are further investigated as hydroboration catalysts, and found to be highly active with strongly
electron-withdrawing ligands.
Chapter 5 describes the ligand development undertaken for improvement of the catalytic
hydrogenation system. Whilst no improved system is ultimately discovered, this chapter outlines the likely direction of successful future work.
Chapter 6 contains experimental details of all the syntheses and reactions performed.
A summary of all numbered structures is included on pages 22-24, and repeated in Appendix E
for ease of reference.