Nitrato complexes of thorium and uranium(IV)

The interactions of nitrate with uranium (1V) and thorium (1V) in the presence of a neutron oxygen donor ligand and in a non-aqueous medium were investigated. Hexamethylphosphoramide and trimethylphosphine oxide were used as neutraldonor ligands. Various simultaneous equlibria were indicated in solution and conditions were established under which solid nitrato complexes, which differ in stoichiometry, could be isolated. The donor action of nitrate towards uranium (1V) was compared to that of chloride, bromide, iodide and the neutral donor ligands. The solid nitrato complexes were characterized by means of their visible and infrared spectra, non-aqueous conductivity and magnetic susceptibility. The coordination modes of the nitrato groups were identified using infrared spectrophotometry. The thermal decomposition kinetics of some of the solid nitrato complexes were studied in vacuum by isothermal thermogravimetric analyses. Energy parameters such as activation energies and enthalpies for similar decomposition reactors were compared and discussed