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Topic: Oxidation state  (Read 4505 times)

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Offline critzz

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Oxidation state
« on: May 27, 2016, 02:31:26 PM »
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?

Offline Borek

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Re: Oxidation state
« Reply #1 on: May 27, 2016, 04:11:21 PM »
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?
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Offline critzz

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Re: Oxidation state
« Reply #2 on: May 27, 2016, 05:30:55 PM »
[Fe(H2O)6]3+, so I'm assuming it has counter-ions for example like [Fe(H2O)6]3+[Cl]33-.


Offline Borek

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Re: Oxidation state
« Reply #3 on: May 28, 2016, 02:41:00 AM »
so I'm assuming it has counter-ions

Yes.
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Offline critzz

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Re: Oxidation state
« Reply #4 on: May 28, 2016, 08:37:48 AM »
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-?


Offline Irlanur

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Re: Oxidation state
« Reply #5 on: May 29, 2016, 08:38:20 AM »
Quote
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.

Offline critzz

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Re: Oxidation state
« Reply #6 on: May 29, 2016, 12:31:46 PM »
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.

Offline Borek

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Re: Oxidation state
« Reply #7 on: May 29, 2016, 02:26:45 PM »
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-.
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