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Organouranium complexes for the insertion and reduction of small molecules

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posted on 2023-06-08, 20:25 authored by Jessica Anne Higgins
This thesis explores the behaviour of U(III) and U(IV) organometallic complexes towards small molecules, with respect to both their reductive activity and insertion chemistry. A range of mixed-sandwich U(IV) organyl complexes of the form U(?-C8H6{1,4-SiiPr3}2)(?-C5Me5)(R) (= U(COTTIPS2Cp*(R), where R = CH3, CH2Ph, CH2TMS, CH{TMS}2) have been synthesised and the products of their reactions with CO2, CO, and H2 (?2-carboxylates, ?2-acyls, and a monomeric terminal hydride) have been characterised – all of which are formed under mild conditions (< 1 atm of gas, sub-ambient temperature). The hydride also inserts CO2 to yield a formate, U(COTTIPS2)Cp*(?2-O2CH), which is the first example of its kind, and inserts CO to form cis-enediolate, {U(COTTIPS2)Cp*}2(µ-?1:?1-OCH=CHO). A rare primary amido, U(COTTIPS2)Cp*(NH2), and its CO2 insertion product, U(COTTIPS2)Cp*(?2-O2CNH2), have also been characterised. The latter is the first crystallographically characterised U(IV) primary carbamate. Deprotonation of the parent amido yield an anionic U(IV) terminal primary imido, [U(COTTIPS2)Cp*(NH)][K(18-crown-6)]. U(III) and U(IV) complexes containing a dianionic diamidoamine ligand, [N{SiMe3}(CH2CH2N{SiMe3})2]2- (= N'N'2) have been synthesised. It has been found that the migration of a SiMe3 group along the ligand backbone occurs spontaneously when bound to uranium. Reduction of the U(IV) compound U(N'N'2)Cp*Cl with KC8 yields either the U(III) product, U(N'N'2)Cp*, or bridging arene products, {U(N'N'2)}2(µ-?6:?6-C6H5R) (where R = H, Me), depending on the reaction stoichiometry. Further reactivity of these diamidoamine complexes with small molecules is also discussed.

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  • Published version

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313.0

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  • Chemistry Theses

Qualification level

  • doctoral

Qualification name

  • phd

Language

  • eng

Institution

University of Sussex

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  • Yes

Legacy Posted Date

2015-03-25

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