Crown Thioether Chemistry of Iron(II/III): Synthesis and Characterization of Low-spin Bis(l,4,7-trithiacyclononane)iron(III) and Crystal Structure of [fe^II([9]anes3)([9]anes3(0))](c10₄)₂-2nac10₄'H₂0

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 [Fe^mS₆]³⁺core, [FeL₂]³⁺is a strong one-electron oxidant (E_1/2= +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 [Fe^IILL¹](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.