Contribution to the coordination chemistry of penta, hexa and heptavalent ions of 5f elements

This report has two main parts in which are discussed results dealing with: - aquo and hydroxo complexes of penta, hexa and heptavalent ions of 5f elements - pseuso halides complexes of these ions (SCN^-, N₃^-, CN^-). It has been shown, by spectrophotometric and electrochemical measurements that U (V) possesses an aquo ion more acid than the known UO₂⁺ ion. This form is observed as insoluble hydroxid near pH 3.0 or as soluble polynuclear hydroxo complexes at lower pH. Hydroxo anionic complexes of U (VI) have been observed and one can precise the mecanism of hydrolysis of UO₂⁺⁺ ions beyond he hydroxid UO₂(OH)₂. At pH 9 to 12, polynuclear species with low negative charge have been observed. At pH 13, others OH^- ions enter in the coordination sphere of UO₂⁺⁺ and mononuclear species are obtained. Reduction of polynuclear species leads to mixed hydroxo complexes of 'blue type'. Studies of hydrolysis of NpO₂⁺ allow to propose an hydrolysis mechanism similar to UO₂⁺⁺ one. With electrochemical methods that in acidic media Np (VII) is present as NpO₃⁺ ions. Solubility product of NpO₃OH has been measured. The second part is devoted to pseudohalides complexes of UO₂⁺⁺, UO₂⁺ and NpO₂⁺ ions.