Is glycinate ligand a monoanion or a zwitterion? Glycinate as far as I can guess from the structure is a monoanion with negative charge on oxygen atom (though that negative charge is resonating). But when I used this logic in my exam it costed me 4 marks. I don't understand why.
Is it because it is derived from glycine in strongly basic medium which is not a monoanion but a zwitterion? Still, it doesn't seem to be making sense.
,Assuming glycinate is in its anionic form ($\ce{H2N-CH2-CO2^-}$), one thing to consider is it may not act just as a simple anionic ligand like chloride or hydroxide.  You can count off four atoms from the nitrogen to either carboxyl-ate  oxygen and those atoms both have available electron pairs.  So you add the metal atom and you get a five-membered ring similar to that formed with ethylenediamine.  Thus, glycinate anion may act as a chelating agent.