I'm trying to construct a molecular orbital correlation diagram for a tetrahedral compound [NiX4]2- considering the ligand pi-orbital basis. I've already constructed a diagram wherein the only the sigma-orbital basis is considered. In that diagram, I had 12 electrons for the nickel (10 in 3d - 6 with T2 symmetry and 4 with E symmetry; 2 in 4s with A1 symmetry) and 4 electrons for the 4 ligand sigma orbitals (3 with T2 symmetry and 1 with A1 symmetry).
I've determined that the ligand pi-orbital basis is represented by T2+T1+E...I'm just having trouble filling in the electrons at this point.
Assuming that the ligand is a halogen or similar pi-donor (so the complex has 16 electrons overall), I don't think the ligand pi-orbital basis can remain empty as this would result in a similar diagram to the sigma only case. But I don't know how to place my electrons. Can someone please provide some guidance? The T1 orbitals will stay nonbonding, and it would be nice to have the 3d electrons with E symmetry interact with the ligand pi-orbitals with E symmetry, but I don't know how to make this work...
The Attempt at a Solution
See above for description.