Haven't you got that a little bit wrong?
(Original post by Bradshaw)
You can determine the splittings of the orbitals from the symmetry of the complex. This is beyond A level I'm afraid, but you can think of it simply like this:
The easiest example is an octahedral complex. Let the z-axis run vertically (through two of the ligands). The
orbital will point towards these ligands. This creates a favourable overlap, lowering the energy of this orbital. Similarly, the
orbitals will point towards the 4 ligands in the x-y plane, lowering the energy of these orbitals. This gives us three orbitals with low energy. The
orbitals do not point towards the ligands and are thus higher in energy.
The d orbitals are all raised in energy as the interaction between the ligand orbitals and the d orbitals is a destabilising one.
In an octahedral complex, the z^2 and x^2-y^2 (eg set) are both raised in energy more than the others (xy, xz and yz - the t2g set). This is because if you consider the ligands to lie on each of the 3 axes, the eg set point straight at the ligands and are hence raised in energy, and the t2g set point between the ligands and are not raised in energy as much. You can also tell that the orbitals are split in this fashion by looking at the symmetry tables for the Oh point group. The way you described it doesn't give you the orbital degeneracies in the right way.
You're right... As far as I understand things.
Last edited by illusionz; 05-06-2012 at 18:56.