[Twickel]

Hi
So I understand that pi electron donors lower the splitting while pi acceptor ligands increase the splitting of the t2g and eg orbitals.

How do I know which ligands are pi donating and pi accepting? For example PPH3 is pi accepting, but how do I know? I can not draw the molecular orbital diagram for this complex..

Then there are linkage isomers, why is NO2- i accepting and ONO- pi donating?

Your help will be much appreciated.

[dayglo]

you might find this site to be useful: http://www.chm.davidson.edu/vce/coordchem/Ligands.html

you should try to draw the molecular orbital diagram, but failing that you can get a sense of what the behavior might be if you know the type of orbital the ligand can use to interact with the metal and whether it is filled or not. Leaving out the complicating features of group theory and nonideal symmetry, your ligand needs to have pi type (usually coming from ligand p type orbitals).

I can go into more detail if you have any more questions.