Actinide complexes peroxides

Because of the ease of oxidation of protactinium(IV) and uranium(IV), peroxides and peroxo complexes are limited to their higher oxidation states. The compounds M04"JcH20 precipitated from dilute acid solutions of neptunium(IV) and plutonium(IV) by hydrogen peroxide appear to be actinide(IV) compounds. Soluble intermediates of the type [Pu( U-02)2Pu]4+ are formed at low hydrogen peroxide concentrations. 

Actinide(V) and (VI) ions form soluble complex ions with peroxide ion in slightly alkaline medium, whereas actinide(III) and (IV) ions precipitate as hydroxides. Actinide(VI) ions in slightly alkaline hydrogen peroxide solution precipitate upon addition of cobalt(III) complex salts. Figure 7 shows the precipitation behavior of U(VI) peroxo complex ion with the following kinds of cobalt(III) complex salts ... 

For the other actinide elements the usual starting material will be the dioxide. Although these reactions appear to be simple, they are in fact quite complex. Uranium trioxide as prepared by thermal decomposition of uranyl nitrate hexahydrate, uranium peroxide, or ammonium diuranate may exist in any one of at least four crystal modifications and in an important amorphous form. The reduction of U03 appears to be related both to the crystal form and to the surface area, and depending on these and perhaps other still unspecified variables, the hydrofluorination reaction on the... 

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