From the diagram below it is easy to see why molcules obeying theis energy diagram can only have four ligand, if there were any more it would be energetically unfavourable. It is important to familiarise yourself with these diagrams and try to understand what they mean.
Molecular orbital diagram of a tetrahedral complex.
What does a MO diagram of a square planar molecule look like?
Author: Sally Robinson, date of modification: 20 March 2003