Colour obtained will be pale blue with 1:1 mixture, blue\/purple with 1:2 and violet with 1:3 molar ratio of hexaqua nickel(II) chloride to ethylenediammine (bidentate ligand). When [Ni(H2O)6]2+ is mixed with ethylenediamine in excess 1:3 molar ratio, ethylenediamine(en) displaces H2O to form a chelate. Chelates are more stable complexes. [Ni(H2O)6]2+(aq)