2 HIO3 + 10 FeSO4 + 5 H2SO4 → 5 Fe2[SO4]3 + I2 + 6 H2O
This is a complexation reaction: Fe2[SO4]3 is the formed complex.
This is an oxidation-reduction (redox) reaction:
2 IV + 10 e- → 2 I0 (reduction)
10 FeII - 10 e- → 10 FeIII (oxidation)
HIO3 is an oxidizing agent, FeSO4 is a reducing agent.