This thesis describes the synthesis and reactivity studies of the actinyl dications [AnO2]2+ in a variety of oxidation states. Chapter one introduces the importance of the chemistry of actinyl cations in nuclear technology and in the environment, and in particular the chemistry of uranyl dication, which is very stable in the higher oxidation state and considered to be chemically-inert. In Chapter two, on the synthesis of the new macrocyclic Pacman complex [UO2(S)(H2L)] is reported and its reactivity with differing amounts of lithium bases evaluated, so providing insight into the single electron reduction of the uranyl dication. Chapter three is focused on the reactions of the lithiated complexes generated in Chapter two towards acid and silyl sources to obtain complexes in which the oxogroup is further functionalised and to provide mechanistic insight into uranyl immobilisation. Chapter four evaluates the reactivity of the uranyl(VI) Pacman complex [UO2(S)(H2L)] with [Zn{N(SiMe3)2}Cl] to obtain another routes to form the complex [(Me3SiO)UO(THF)(ZnCl)2(L)] and the reactivity with different sources of potassium base, and provides a comparison to the analogues Li-base reactions described in Chapter two. The reactivity of the potassiated and lithiated complexes towards a variety of transition metals are described. Chapter five contains a summary and conclusions on this work. Chapter six presents full experimental details and analytical data.