Sulfur K-edge extended X-ray absorption fine structure spectroscopy of homoleptic thiolato complexes with Zn(II) and Cd(II)

The sulfur K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy is applied to homoleptic thiolato complexes with Zn(II) and Cd(II), (Et4N)[Zn(SAd)3] (1), (Et4N)2[{Zn(ScHex)2}2(μ-ScHex)2] (2), (Et4N)2[{Cd(ScHex)2}2(μ-ScHex)2] (3), (Et4N)2[{Cd(ScHex)}4(μ-ScHex)6] (4), [Zn(μ-SAd)2]n (5), and [Cd(μ-SAd)2]n (6) (HSAd = 1-adamantanethiol, HScHex = cyclohexanethiol). The EXAFS results are consistent with the X-ray crystal data of 1–4. The structures of 5 and 6, which have not been determined by X-ray crystallography, are proposed to be polynuclear structures on the basis of the sulfur K-edge EXAFS, far-IR spectra, and elemental analysis. Clear evidences of the S⋯S interactions (between bridging atoms or neighboring sulfur atoms) and the S⋯Cfar interactions (in which Cfar atom is next to carbon atom directly bonded to sulfur atom) were observed in the EXAFS data for all complexes and thus lead to the reliable determination of the structures of 5 and 6 in combination with conventional zinc K-edge EXAFS analysis for 5. This new methodology, sulfur K-edge EXAFS, could be applied for the structural determination of in vivo metalloproteins as well as inorganic compounds.