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Topic: Acidity of metal-aqua complexes!  (Read 5251 times)

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Offline Winga

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Acidity of metal-aqua complexes!
« on: October 03, 2004, 09:20:52 AM »
For this two complexes:
[Al(OH2)6]^3+   &   [Fe(OH2)6]^3+

The Al^3+ one is moe acidic. Why?

I have found 2 answers:

1. The charge to size ratio of Al^3+ is higher so the charge-charge repulsion of this metal center and the acidic proton is also higher.

2. The Al^3+ has a higher polarizing power that it polarizes the O-H bond.

Which one is more suitable for explaining this case?

Is there any better explanation?


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Re:Acidity of metal-aqua complexes!
« Reply #1 on: October 03, 2004, 05:20:26 PM »
Who cares, though I prefer the second.


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Re:Acidity of metal-aqua complexes!
« Reply #2 on: October 04, 2004, 11:01:13 PM »
The difference in acidity is almost certainly due to the relative stabilities of other metal-hydroxy complelexes ie Al(OH)2 + is probably more stable than Fe(OH)2 + resulting in more protons being formed in the Al solutions

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