First of all I am confused how something can be pi neutral? something either does or doesn't have filled p orbitals for example. given something I have never seen acting as a ligand before like trimethylphosphate how can I work out whether this is pi accepting, donating or neutral? I am thinking the donor atom would be the oxygen bonded to the Me group and P but do I only consider the orbital of the donor atom?
For a tetragonal Cu(II) complex how can a ligand even act as pi donating if since the t2g orbitals on the metal are filled?
Sorry about this messy question, I am very confused about this in general, I would be so grateful if someone could help me understand this