Bimetallic actinide complexes for small molecule activation

Abstract

The work described in this thesis concerns the synthesis of actinide complexes and their reactivity towards small unsaturated molecules. Complexes bearing tetraphenoxide, borohydride and boroxide ligands have been evaluated. Additionally, work towards the synthesis of heterobimetallic uranium transition metal complexes and their applications in catalysis is discussed. Chapter one reviews important organoactinide complexes reported in the literature which effect chemical transformations on small unsaturated substrates. Actinide complexes supported by aryloxide or borohydride ligands are reviewed, along with actinide complexes in which metal p-arene interactions are present. Chapter two reports the synthesis and characterisation of a set of tetraphenol ligands, in addition to a number of attempted synthetic routes to tetraphenol ligands with alternate substitution. The chemistry of those tetradentate aryloxide ligands is introduced with bimetallic uranium(IV) and thorium(IV) complexes using different An(IV) and U(III) precursors. Chapter three reports the synthesis and characterisation of monometallic uranium and thorium complexes using a tetraphenol ligand. The varying chemistry between the two similar An(IV) ions, where the uranium complexes exist as a mixture of oligomers and the thorium complexes remain as well defined mononuclear complexes, is discussed within. A range of base adducts of mononuclear actinide complexes are reported, including a thorium trimethylsilylazide complex, a rare example of a metal organoazide. Chapter four describes the synthesis of homoleptic boroxide and heteroleptic borohydride complexes of uranium(III). The reactivities of these complexes with small unsaturated molecules are assessed, including the reaction of a low coordinate uranium(III) boroxide complex towards CO2 to provide a dinuclear uranium carbonate bridged complex. Chapter five introduces work towards heterobimetallic uranium transition metal complexes carried out in the Arnold group. The application of these complexes towards ring opening polymerisation chemistry is discussed in addition to investigations into the incorporation of transition metals into uranium(IV) complexes. Chapter Six presents the detailed experimental methods used to carry out this research.