The oxidation of purple [FeL2]2+, where L represents the cyclic crown thioether 1,4,7-trithiacyclononane (C6Hi2S3), with Pb02in 1 M sulfuric acid yielded green [FeL2]3+, which has been isolated as [FeL2](PF6)3and characterized by magnetic susceptibility measurements and its electronic and Mossbauer spectra to contain a Jahn-Teller-distorted low-spin [FemS6]3+core, [FeL2]3+is a strong one-electron oxidant (E1/2= +0.98 V vs ferrocenium/ferrocene in acetonitrile), which oxidizes Cl~ and H202. In contrast, oxidation of [FeL2]2+in aqueous solution with Na2S208afforded upon addition of NaC104two crystalline materials: mixed crystals of [FeL2][FeLL1](C104)4and [FeIILL1](C104)2-2NaC104*H20, where L1represents 1,4,7-trithiacyclononane 1-oxide. Electronic spectra, 1H NMR measurements, and a single-crystal X-ray diffraction study of the latter material showed that the iron center is still in the oxidation state +11, is low spin, and is coordinated to one 1,4,7-trithiacyclononane and its oxidized form 1,4,7-trithiacyclononane 1-oxide, forming a pseudooctahedral [FeS6]2+core. [FeLL1](C104)2-2NaC104-H20 crystallizes in the triclinic system, space group P1, with a = 10.145 (7) A, b = 12.323 (6) A, c = 12.465 (6) A, a = 82.91 (4)°, β = 86.09 (4)°, γ = 83.16 (5)°, and Z = 4. These results show that oxidation reactions of coordinated thioether complexes of iron(II) may be either at the metal or at the ligand depending on the nature of the oxidant used.