The tetranuclear iron(III) compound where two μ-oxo bridged iron(III) complexes are bridged by four carboxylato groups of H(dpal), was isolated from the reaction mixture of Fe(dpal)Cl 2 and hydrogen peroxide, implying that hydrogen peroxide contributes to the formation of an oxo-bridge diiron species via O-O bond cleavage (H(dpal)=N,N-bis(2-picolylmethyl)-β-alanine). This suggests that hydrogen peroxide released in H-subunit of human herritin plays an important role for storing of iron atoms in L-subunit of human ferritin.