# Oxidation No. of Fe and NO in Nitroprusside ion [duplicate]

For the complex $$\ce{[Fe(CN)5NO]^{2-}}$$ wikipedia cites that the oxidation no. of Fe is +2 and that of NO is +1. CN being -1 the net charge thus becomes -2. However at certain places I read that NO is neutral and Fe is in its +3 oxidation state. In both cases the net charge is -2. However which of the two is correct ?

• – Martin - マーチン Oct 30 '18 at 9:18
• The Wikipedia articles states that by epr experiment the Fe is $d^6$ so $\ce{Fe^{2+} }$. If NO can be formally either 0 or +1 you cannot determine which without some experimental data. – porphyrin Oct 31 '18 at 10:06

The thing about nitrogen monoxide ($$\ce{NO}$$) is that it can be both a neutral compound and an ionic compound, depending on the context. This problem is about complex ions, which consist of a metal cation and supporting 'ligands.' Ligands are entities/molecules which bind to a metal cation to form a complex or coordinate ion.
According to this article, in $$\ce{[Fe(CN)_5NO]^{-2}}$$, $$\ce{Fe}$$ is the metal cation, and $$\ce{CN^{-1}}$$ and $$\ce{NO}$$ are the supporting ligands. Given that the ion CN has a charge of -1, that will be its oxidation number. NO is neutral, so it has no oxidation number. Putting this all together:
$$\ce{Fe} + 5\cdot(-1) + 0 = -2\ \ \ \$$ - - - - - - -> $$\ \ \ \ \ce{Fe} = +3$$
Therefore, iron has a charge and an oxidation number of +3. ($$\ce{Fe^{+3}}$$)