Di-Amido Xanthene-Stabilised Reactive Main Group Compounds for Small Molecule Activation

Abstract

This thesis describes the use of a xanthene-bridged di-amido ligand, termed "NON", towards the kinetic stabilisation of several types of reactive main group compounds, with the eventual goal of employment in small molecule activation. This extends across a variety of compound types, which has in turn meant that each chapter is written in a somewhat self-contained fashion.

Chapter 1 commences with a broad overview of main group chemistry, with particular focus given to its historical development - beginning with the preparation of "Cadet's fuming liquid" in the mid-18th century, and concluding with Robert West's report of the first silicon-silicon double bond, widely credited for sparking a revival of interest in the field. The NON ligand is also introduced, and contrasted against the backdrop of commonly-employed ligands throughout modern main group chemistry.

Chapter 2 pertains to low-valent s-block chemistry (with subsumption of the group 12 elements as well), and begins with a relatively detailed introduction to the preparation, electronic structure and reactivity of these compounds - both the more-common homo-bimetallic dimers, as well as the less-understood open-shell monometallic counterparts. The coordination chemistry of the NON ligand to said elements is discussed, following which the preparation of a potential s-block radical is described. Characterisation of its electronic structure and reactivity, including the difficulties encountered therein, constitutes the remaining body of work.

Chapter 3 addresses the catalytic efficacy (or lack thereof) of extant group 14 tetrylene complexes in redox-active cross-coupling cycles. Previous reports of oxidative additions and reductive eliminations are discussed, highlighting the potential of tetrylenes in performing redox catalysis. The amenability of NON-ligated tetrylenes towards oxidative additions is investigated, showcasing the flexibility of the xanthene backbone through a "hinging" equilibrium. Subsequent attempts at transmetallation and reductive eliminations are also discussed.

Chapter 4 involves both the preparation and reactivity of molecular organocalcium compounds. Following an induction to both of these aspects across archetypal and molecular organocalcium complexes, the nucleophilicity of existing neutral instances is highlighted. The preparation of NON-ligated analogues, now formally anionic in nature, is described alongside numerous demonstrations of their subsequent reactivity. The discovery of an unorthodox preparative route to these compounds is also included.

Chapter 5 briefly discusses the aggregation chemistry of alkali metal organometallics, with the small body of work that follows describing a convergent, thermodynamically-governed rearrangement operative for both the group 1 metals as well as thallium.

Finally, the chief findings of this thesis are summarised with the supporting information appended thereafter. Show more