First steps to carborane frustrated Lewis pair chemistry
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Chapter 1 provides an introduction to heteroborane chemistry with particular attention on the substitution of Lewis acid and Lewis base groups onto carborane cages. The various methods used to assess Lewis acidity and basicity are discussed. An introduction to frustrated Lewis pairs (FLPs) is also given. Chapter 2 reports the synthesis and characterisation of Lewis acid carboranes, with the first examples of catecholboryl-carboranes. The Lewis acidities of a series of Lewis acid carboranes were ranked using a modified Gutmann-Beckett experiment and compared to that of B(C6F5)3 for use in FLP catalysis. Chapter 3 reports the formation of novel carboranylphosphines based on 1,1ʹ-bis(meta-carborane). The characterisation of a series of (carboranyl)phosphine selenides is reported and the basicity of the parent (carboranyl)phosphine is ranked based upon 1JPSe. The relationship between 1JPSe and the P=Se bond length is explored for the series of (carboranyl)phosphine selenides and the relationship between the experimental 1JPSe and the DFT calculated proton affinity is investigated. Chapter 4 explores the catalytic activity of Lewis acid and Lewis base carboranes as FLP catalysts in Michael addition and hydrosilylation reactions. Chapter 5 discusses preliminary investigations into the synthesis of intramolecular FLP carboranes. The synthesis and characterisation of the first example of an intramolecular FLP carborane is reported, along with assessment of the Lewis acidity and basicity of the compound for possible application in hydrosilylation catalysis. Chapter 7 contains the experimental details for the compounds and catalytic conditions discussed. Appendix A is the crystallographic tables for all compounds studied by XRD in this thesis.