Dioxygen heterolytic bond cleavage

It may be reasonable to argue that this further activation is achieved in several ways. The acid-catalysis required for Gal and de Bruin complex [Rh(/c -bpa)(cod)](PF6) to react with dioxygen can be used to protonate the peroxo compoimd (Scheme 10) to a hydroperoxo species. This is a way to achieve further activation of dioxygen, since it decreases the nucleophilic character of the peroxo hgand and makes interaction with the coordinated olefin easier. Recent works by Moro-oka [88,89] and Braun [90] (Scheme 15) have shown that peroxorhodium complexes can be protonated to hydroperoxo compounds. However, the addition of a second mole of acid leads to hydrogen peroxide ehmination rather than to the highly electrophilic oxo species (M = O) that could result from the heterolytic cleavage of the O - O bond with removal of water. 

The key to both the stereochemistry and energy of the heterolytic cleavage of dioxygen is the polarization of the 0—0 bond induced by the bridging interaction between the two iron centers. Thus, with an additional electron in the proximal copper-iron pair, the 0—0 bond is more polarized in D than in A, In this way both the energy and polarity of the... 

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