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.