Coordination Compounds

If a didentate ligand ethane-1, 2-diamine is progressively added in the molar ratio en : Ni :: 1: 1, 2 : 1, 3 : 1 to \(\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}\) aq solution, following co-ordination entities are formed.

I. \(\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_4 \mathrm{en}\right]^{2+}(a q)\) - pale blue

II. \(\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_2(\mathrm{en})_2\right]^{2+}(\mathrm{aq})\) - blue/purple

III. \(\left[\mathrm{Ni}(\mathrm{en})_3\right]^{2+}(\mathrm{aq})\) - violet

The wavelength in \(\mathrm{nm}\) of light absorbed in case of I and III are respectively