The oxidation of organic compounds by hydrogen peroxide, catalysed by transition metal derivatives, e.g. V(V), Mo(V1) and W (VI) complexes, involves the formation of peroxometal complexes. These are much more efficient oxidants than hydrogen peroxide so that the catalysed reactions are of remarkable synthetic significance. Several peroxometal complexes can be isolated and used as stoichiometric oxidants. An appealing feature of these oxidants is their versatility, as demonstrated by the fact that they are able to oxidize substrates such as alkenes, alcohols, ketones, sulphur, phosphorus and nitrogen derivatives and even aromatic and aliphatic hydrocarbons. Either polar or radical oxidations may take place. The reactivity depends on the nature of the metal and especially on the nature of the ligands coordinated to the metal. Therefore, an important goal consists in predicting the reactivity of peroxometal complexes on the basis of their structural features. Examples presented demonstrate that structure-reactivity correlations may be established. However, the effect of the ligands appears to be complex so that care must be exercized in drawing general conclusions.
Peroxidic compounds are widely used as stoichiometric oxidants of organic compounds.',' Peroxides which have found synthetic applications't2 include alkyl hydroperoxides, organic peracids and dioxiranes, all, at least formally, derived from hydrogen peroxide, by substitution of one or both hydrogen atoms. Therefore, in all these molecules a relatively weak (120-190 kJm01-')~ 0-0 bond is present. In the oxidative process this bond is cleaved. Two main modes of can be envisaged. If the bond is cleaved heterolytically , polar oxidations will take place, whereas if the cleavage is homolytic, radical oxidations will be observed. In polar