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Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: Winga on November 08, 2004, 09:10:13 AM

Title: About MO diagram of octahedral complex
Post by: Winga on November 08, 2004, 09:10:13 AM: The metal center is d2sp3 hybridized. The 6 d2sp3 orbitals overlap with the orbitals of each 6 ligands.

The question is that, the 6 d2sp3 orbitals should be degenerated, are they?
After forming a MO, the energy levels of bonding orbitals a1g, eg & t1u are not the same, why?
Title: Re:About MO diagram of octahedral complex
Post by: Demotivator on November 08, 2004, 11:36:09 AM: No, not necessarily degenerate.
This might help.
http://www.wellesley.edu/Chemistry/chem341/hybridization.html
Title: Re:About MO diagram of octahedral complex
Post by: Winga on November 08, 2004, 01:01:56 PM: Are all the Metal-Ligand bond strengths/lengths equivalent?

So the effective overlaps of all d2sp3-orbitals with each Ligand-orbital should be the same, and the energy level of each new bonding MO should also be the same!
Title: Re:About MO diagram of octahedral complex
Post by: Demotivator on November 08, 2004, 01:24:11 PM: Yes, the M-L bond strengths, etc are all equivalent.
That does not mean the underlying bonding MOs are equivalent (if you read carefully) because of symmetry differences in the MOs. One should also realize that MOs are delocalized over the molecule, so the resulting bonds are the net sum of the underlying MOs responsible for that set.
Bonds are a result of Mos but MOs are not bonds. For example, You might have a single bond (2e). An MO diagram might show two bonding MOs with 4e and one antibonding with 2e. The single bond is a result of the sum of the three contributing MOs.
Title: Re:About MO diagram of octahedral complex
Post by: Winga on November 10, 2004, 07:25:41 AM: So, can I find out the strength of a bond (not bond order, e.g. just a single bond) compare with other bonds (just comparison not exact value) in a MO diagram?
Title: Re:About MO diagram of octahedral complex
Post by: Demotivator on November 10, 2004, 09:28:15 AM: Yes, since the MO diagram is drawn on an energy scale.
Title: Re:About MO diagram of octahedral complex
Post by: Winga on November 10, 2004, 09:37:33 AM: But I don't know how to determine the 6 M-L bonds are equivalent by its octahedral MO diagram!
Title: Re:About MO diagram of octahedral complex
Post by: Demotivator on November 10, 2004, 11:18:01 AM: It can get complicated but,
Although, the symmetries of the MOs are different (eg, t1u, a1g), all of them conform with the O_h character group for an octahedral complex with identical ligands and those ones have symmetries of sigma bonds. Therefore those MOs relate to the M-L bonds.

http://hk2.uwaterloo.ca/310/2001_2.html
Title: Re:About MO diagram of octahedral complex
Post by: Mitch on November 10, 2004, 04:35:37 PM: The tricky question is what is the bond order for an octahedral complex. It's less straight forward than on imagines.