How I will get Nickel free ligand from a six coordinated Ni(II) complex ? Disodium salt of EDTA is not working sometimes and as my ligand backbone contains ester, I can not use ammonia/ DMGH2.
NaCN or KCN addition is suitable (e.g., cyclam recovery after synthesis on Ni2+-matrix). Na2[Ni(CN)4] is final by-product (very hydrophilic), reaction progress is visible by color change (in some seconds)
I would also try the method proposed by Paramita. [Ni(DMG)2] is a very stable complex and additionally drops out of solution if a suitable pH and ionicity of the aqueous is adjusted. And please, Saikat, tell us if and how it worked!