[Winga]

e.g. a square planar complex

For dxz,dyz ---> dz² transition, if there is no electron in dz² orbital of metal centre, when a solvent molecule acts as a ligand to attach the metal centre at z-axis, then, the dz² is stablized or destabilized?

[skyaintsnow]

I'd put destablized. dz², its spatial arrangement causes repulsion with ligand electrons

Hey wait, square planar, how come d² is involved?

[Winga]

If there is no electron in dz², how comes the electron-electron repulsion with ligand's lone pair.

You mean the empty dz² orbital repels ligand's lone pair?

[skyaintsnow]

sorry, I was talking about octahedral. I reconsidered it, maybe only d_x²-y² has repulsion. After splitting all other orbitals are stablized.

[Winga]

I just wonder that there is destabilization of filled dz² orbital when a ligand attaches to the metal centre at z-axis, while there is stabilization of unfilled dz² orbital when a ligand attaches to the metal centre at z-axis.

[Winga]

Can anyone help?

[AgG]

the crystal field arises as a result of the inherant geometry of the system whether or not the orbitals are filled.  The crystal field splitting diagram for a five coordinate square pyramidal complex looks similar to square coordinate complexes but the energy of the z2 orbital is higher than it is in the square planar complex as a result of interaction with the new ligand.