Investigations into the Physical Properties and Reactivity of Thorium(III) Complexes

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Abstract

Investigations into the Physical Properties and Reactivity of Thorium(III) Complexes: A thesis submitted to The University of Manchester for the degree of Doctor of Philosophy in the Faculty of Science and Engineering.Since the first full structural characterisation of a thorium(III) complex 30 years ago, the chemistry of the highly reactive oxidation state has been largely neglected with respect to related uranium(III) chemistry. Despite the employment of nuclear technologies across the globe since the 1950’s, the relatively poor understanding of the actinides is somewhat surprising, in particular the models used to describe their bonding. Herein, this work presents an investigation into the reactivity of a thorium(III) complex, [Th(Cp'')3] (Cp'' = {C5H3(SiMe3)2-1,3}-); the synthesis and full characterisation of a new thorium(III) complex, [Th(Cptt)3] (Cptt = {C5H3(tBu)2-1,3}-); and the synthesis of two new hexadentate trisanilido ligands which are shown to stabilise uranium(III) and offer highly flexible coordination modes.All of the compounds presented were characterised via a range of analytical and spectroscopic techniques. [Th(Cptt)3] is shown to react with a series of small molecules, displaying elevated reactivity in the majority of cases to the similar uranium(III) complexes. In this work, [Th(Cptt)3] is shown to activate: P4, pyridine, 4,4′-bipyridine, Ph2CO, MeCN, CS2 and CO2, to form dimeric thorium(IV) complexes. The reactivity studies presented provide the first real measure of the reductive capability of the thorium(III) oxidation state.The first pulsed EPR spectroscopy experiments on actinide containing complexes are reported for a pair of new complexes, [M(Cptt)3] (M = U, Th), with the results allowing the direct calculation, via measurement of hyperfine coupling constants, of bonding between the actinide elements and the supporting ligand framework. The results indicate that comparative covalent character is found for the studied actinide complexes with the only other f-element complex characterised by this technique, [Yb(Cp)3], challenging conventional bonding models. Alasdair FormanuikAugust 2016

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Organometallic; Thorium

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