# O2 in a 3- oxidation state?

Has diatomic oxygen ever been observed with a 3- charge, i.e. $\text{O}_2^{3-}$? Have any ab intio calculations been done on this ion?

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Two things: firstly, when referring to oxidation states, the sign comes before the number, so a thing is in oxidation state +3 or -1, for example. Secondly, an atom has an oxidation state, a molecule has a charge. For charges, the sign comes after, so 2- or 2+. –  Aesin Dec 8 '12 at 15:47
Thanks, I have edited the question to reflect your comment. –  Max Radin Dec 9 '12 at 21:01
One should notice that the simple existence of such a species is not obvious. Anions always have the possibility to evolve through loss of an electron, which is not the case for positively charged species. Computation of electron affinities is not obvious, as ab initio calculations would "force" the electron to remain bound. Therefore one has to add numerous diffuse orbitals and consider that the presence of the extra electron in diffuse orbitals should be interpreted as a sign of unstability of these species. –  PLD Dec 18 '12 at 12:52
anions form from Gain of electrons and cations form from Loss of electrons. Not the other way around. –  caters Aug 9 at 21:51

I don't know of (and a quick search couldn't reveal) any studies on the $\ce O_2^{3-}$ ion. Note that in this ion, oxygen wouldn't have an oxidation state of –3, but –1.5.
Yes, it is, in $\ce{H3O2}$. This is from an a CCB bond. However, this is highly unlikely.