A computational study and magnetic susceptibility measurements of three homonuclear Fe(III) Keggin structures are herein presented: the [FeO4@Fe12F24(mu-OCH3)(12)](5-) anion (1), the [Bi6{FeO4@Fe12O12(OH)(12)}(mu-O2CCCl3)(12)]+ cation (2) and its polymorph [Bi6{FeO4@Fe12O12(OH)(10)(H2O)(2)}(mu-O2CCF3)(10)](3+) (3). These results are contrasted with the exchange interactions present in the previously characterized [Fe-6(OH)(3)Ge2W18O68(OH)(6)](11-) and [H12As4Fe8W30O120(H2O)(2)](4-) anions. The computational analysis shows that the most significant antiferromagnetic spin coupling takes place at the junction between each of the {Fe3O6(OH)(3)}/{Fe3F6(OCH3)(3)} framework motifs, a possibility that had been previously discarded in the literature on the basis of the Fe-Fe distances. For all the examined iron(III) Keggin structures, it is found that the magnitude of the magnetic couplings within each structural subunit follows the same trend.