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Author Topic: Copper (II) complex ion  (Read 8664 times)

Offline cuso4

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Copper (II) complex ion
« on: 30/04/2004 19:14:23 »
This question has been bothering me a while now, maybe Jay can put my mind at rest.

Copper (II) ions form the blue hexaaqua ion with water, [Cu(H2O)6]2+. On adding excess ammonia the blue colour changes into a beautiful deep purple as the tetraammine ion forms, [Cu(NH3)4(H2O)2]2+.

Ligand substitution occurs, but why are only 4 H2O ligands are replaced and not all six?



Offline Ylide

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Re: Copper (II) complex ion
« Reply #1 on: 01/05/2004 18:52:43 »
Ligand chemistry is not exactly my forte, but if I had to make an educated guess, it would be that it's related to the energy and symmetry of the molecular orbitals of the ligand.  Atomic orbitals combine to form molecular orbitals, and they tend to do it with species of an energy that is very close to their own.  

What I'm speculating without doing the calculations (they're kind of complex) is that copper II ion has 4 orbitals that are slightly higher or lower than the other two, (and consequently closer to ammonia's AO energy) and those are the ones that the ammonia bonds with.  

I could be completely wrong, of course.  [:p]  I have to study for a p-chem final this weekend, I'll do the calculations and let you know what I come up'll be good practice.

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The Naked Scientists Forum

Re: Copper (II) complex ion
« Reply #1 on: 01/05/2004 18:52:43 »


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