# Stability order of chelate complexes of nickel and iron

Which stability order is correct?

1. $$\ce{[Ni(en)2]^2+} > \ce{[Ni(dmg)2]}$$
2. $$\ce{[Fe(edta)]^2-} > \ce{[Fe(en)3]^3+}$$

In the first case I think the stability depends upon the strength of the ligand so is $$\ce{en}$$ stronger than $$\ce{dmg}$$ to form a more stable compound? As the oxidation state of nickel is same for both the cases.

In the second case the oxidation state of iron is +2 and +3, respectively. But I am confused if the metal with higher oxidation state is more stable or the metal with lower oxidation state is more stable?

Does stability depends upon the number of chelating groups?

• In general, metal with higher oxidation state forms more stable complex. – Zenix Nov 18 '19 at 16:00
• But that does not appear to be the case in the second example where +2 is more stable than +3 of fe – studious Nov 19 '19 at 1:47