Reactions of the μ3-sulfido triiron cluster [SFe3(CO)9]2− with functionalized organic halides and mercury salts: selective reactivity, electrochemistry, and theoretical calculations

Abstract

When the μ₃-sulfido triiron cluster [SFe₃(CO)₉]²⁻ was treated with BrCH₂C(O)OCH₃ in MeCN, the ester-functionalized complex [SFe₃(CO)₉(CH₂C(O)OCH₃)]⁻ (1) was obtained. Cluster 1 displays a SFe₃ tetrahedral core with one of the Fe atoms bonded to an ester ligand CH₂C(O)OCH₃. In contrast, when [SFe₃(CO)₉]²⁻ was treated with dihaloalkanes X(CH₂)_nX′ (X = Cl, X′ = Br, n = 3; X = X′ = I, n = 4) in MeCN, the sulfur-alkylated complexes [X(CH₂)_nSFe₃(CO)₉]⁻ (X = Cl, n = 3, 2; X = I, n = 4, 3) were formed, respectively. Clusters 2 and 3 each exhibits a SFe₃ tetrahedral core with the sulfur atom attached to the halide-functionalized alkyl group. Furthermore, the Hg-bridged di-SFe₃ complex [{SFe₃(CO)₉}₂(μ₄-Hg)]²⁻ (4) was isolated from the reaction of [SFe₃(CO)₉]²⁻ with 2 equiv. of Hg(OAc)₂ in acetone. However, when [SFe₃(CO)₉]²⁻ was treated with HgI₂ under similar conditions, the HgI-bridged cluster [SFe₃(CO)₉(μ-HgI)]⁻ (5) was produced. In addition, complex 4 could be transformed into complex 3 upon treatment with I(CH₂)₄I in MeCN. Conversely, complex 3 could be reconverted into 4 in the presence of Hg(OAc)₂ in an acetone solution. Clusters 1–5 were fully characterized by spectroscopic methods and single-crystal X-ray analysis. In particular, the nature and selective formation as well as electrochemistry of complexes 1–5, which resulted from the different reactive sites (Fevs. S atom) of [SFe₃(CO)₉]²⁻, were also examined and compared systematically by molecular orbital calculations at the B3LYP level of the density functional theory.