Organouranium complexes for the insertion and reduction of small molecules

Higgins, Jessica Anne (2014) Organouranium complexes for the insertion and reduction of small molecules. Doctoral thesis (PhD), University of Sussex.

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Abstract

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(η-C8H6{1,4-SiiPr3}2)(η-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 (κ2-carboxylates, η2-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*(κ2-O2CH), which is the first example of its kind, and inserts CO to
form cis-enediolate, {U(COTTIPS2)Cp*}2(μ-κ1:κ1-OCH=CHO). A rare primary amido,
U(COTTIPS2)Cp*(NH2), and its CO2 insertion product, U(COTTIPS2)Cp*(κ2-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-η6:η6-C6H5R) (where R = H, Me), depending on the reaction
stoichiometry. Further reactivity of these diamidoamine complexes with small
molecules is also discussed.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Life Sciences > Chemistry
Subjects: Q Science > QD Chemistry > QD0241 Organic chemistry
Depositing User: Library Cataloguing
Date Deposited: 25 Mar 2015 11:50
Last Modified: 28 Sep 2015 13:39
URI: http://sro.sussex.ac.uk/id/eprint/53503

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