Ok so I'm confused about the mechanism for this process:

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Now the idea here is that iron first becomes oxidised to Fe(III) by placing an electron in the antibonding orbital of dioxygen. This is followed by the addition of 2 electrons from an external source. This causes the splitting of the O-O bond resulting in the formation of a hydroxide ion. In addition, iron loses another electron to oxygen forming the Iron(IV) oxide species shown.

Now what I do Not understand is the overall charges on the species at the end. I feel as if the original O-Fe(III) bond was considered purely ionic hence the lack of a formal charge on oxygen, yet at the end it seems as if the O=Fe(IV) bond is covalent, otherwise there would be a negative 2 charge on oxygen!

Is there a switch between ionic and covalent formalisms in the middle of this process?

If anyone could help explain the charges with perhaps a curly arrow mechanism to indicate the numbers of electrons on each atom then that would be most appreciated!

  • 2
    $\begingroup$ Quick look into available articles made me think that the first stage is one-electron transfer forming superoxide anion. Since superoxide is extremely reactive, the further steps depend highly on environment, as it would react with first available candidate. $\endgroup$ – permeakra Sep 4 '15 at 9:03

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