[critzz]

Why does Fe(H₂O)6 have an oxidation state of +3? All the H₂O ligands are neutral, so intuitively you'd think Fe-complex is neutral too. Does it delocalize 3 of it's d-electrons over the 6 water molecules equally?

How can you tell just by looking at a complex which oxidation state it occurs in?
How would you for instance determine the oxidation state of Fe(bipy)₃ or even more intricate metal complexes containing neutral groups like NH₃, H₂IO or pyridine?

[Borek]

Why does Fe(H₂O)6 have an oxidation state of +3?

First of all, that's not a correct formula. What happened to the charge?

[critzz]

[Fe(H₂O)₆]³⁺, so I'm assuming it has counter-ions for example like [Fe(H₂O)₆]³⁺[Cl]₃^3-.

[Borek]

so I'm assuming it has counter-ions

Yes.

[critzz]

So essentially you're viewing it as if the counter-ions are directly coordinated to the metal, like FeCl₃ * 6H₂O.
Would that notation be the identical compound as [Fe(H2O)₆]³⁺[Cl]₃^3-?

[Irlanur]

So essentially you're viewing it as if the counter-ions are directly coordinated to the metal, like FeCl3 * 6H2O.
Would that notation be the identical compound as [Fe(H2O)6]3+[Cl]33-?

Not really. the first one doesn't really say anything about how water and chlorine are coordinated. The second one clearly states that the water is directly coordinated to iron and the chlorines are much further away.

[critzz]

Not really. the first one doesn't really say anything about how water and chlorine are coordinated. The second one clearly states that the water is directly coordinated to iron and the chlorines are much further away.

These structures only make sense in a crystal lattice then, huh? The chemical formula (including counter-ions) only represents what fits in the crystal's unit cell.
Sorry for keeping asking.

[Borek]

No idea about iron, but CrCl₃ in aqueous solutions exists as a series of isomers in which central atom is complexed by a mix of water of Cl^-.