Peroxo complexes chromium

Wood, R. M., Aboud, K. A., Palenik, R. C., and Palenik, G. J. (2000). Bond valence sums in coordination chemistry. Calculation of the oxidation state of chromium complexes containing only Cr-O bonds and a redetermination of the crystal structure of potassium tetra(peroxo)chromate(V). Inorg. Chem. 

Further information on peroxo chromium complexes is given in Pascal.3... 

Like other transition metals, notably Ti, V, Nb, Ta, Mo, and W, chromium forms peroxo compounds in the higher oxidation states. Most of them are unstable, and in the solid state some of them are dangerously explosive or flammable in air. Bis(peroxo)chromium(IV) complexes with nitrogen ligands are remarkably stable, e.g., (17-C-XII).40... 

The mechanism of oxygen transfer from the peroxide (29) to the substrate still remains a matter of controversy. Current opinions favor the formation of a high-valent FeO (or Fe =0 or Fe —0-) (30) active species, which acts as a homolytic hydrogen abstractor from the substrate. An alternative mechanism considers the Fe -peroxide complex as the actual hydroxylating reagent, by analogy with the reactivity of vanadium(V)-peroxo and -alkylperoxo complexes and that of chromium(Vl)-peroxo complexes (see below). ... 

An alternative mechanism considers the Fe -peroxide complex as the actual hydroxyiating reagent,by analogy with the reactivity of vanadium(V)-peroxo and -alkylperoxo complexes and that of chromium(Vl)-peroxo complexes (see below). ... 

Similarly, a single peroxidic resonance at 458 ppm has been observed by Curci et al. [255] for the diperoxomolybdenum complex 17 although the peroxo oxygens should not be equivalent in a pentagonal bipyramidal structure of this type. The analogous chromium complex gives two resonances at 772 and 820 ppm in a 1 1 intensity ratio. 

Alkoxo monoperoxo vanadium complexes are also efficient radical oxidants of the alcoholic function164-166 167 again with a radical chain mechanism whose details are indicated in Scheme 16 in the case of 2-propanol. Similar radical peroxo species have been indicated as competent oxidant also in the oxidation of alcohols with bis-peroxo chromium complexes159. 

Figure 17-C-5 The structures of some chromium peroxo complexes mentioned in the text.

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