In the complexes ${\left[Fe{\left(H_{2}O\right)}_6\right]}^{3+}$ $,{\left[Fe{\left(CN\right)}_6\right]}^{3-}$$,{\left[Fe{\left(C_2{O}_4\right)}_3\right]}^{3-}$ and ${\left[FeC{l}_6\right]}^{3-}$, more stability is shown by

${\left[Fe{\left(C_2{O}_4\right)}_3\right]}^{3-}.$ The iron is present in the highest oxidation state $F{e}^{3+}$ and $C_2{O}_4^{2-}$ is a chelating ligand.

Chelates are always more stable complexes