H is reduced, while Fe is oxidized. Note: the oxidation state of H changes from +1 In HI to 0 in H2. the oxidation state of Fe changes from 0 in Fe(CO)5 to +2 in Fe(CO)4I2. CO is a neutral ligand. Solution H is reduced, while Fe is oxidized. Note: the oxidation state of H changes from +1 In HI to 0 in H2. the oxidation state of Fe changes from 0 in Fe(CO)5 to +2 in Fe(CO)4I2. CO is a neutral ligand..