Preparation and structures of tellurium(IV) halide complexes with thioether coordination

The first chalcogenoether complexes of Te(IV) chloride and bromide are prepared by reaction of the thioether with a suspension of TeX₄ in anhydrous CH₂Cl₂, and the products characterised by IR, Raman, ¹H and ¹²⁵Te{¹H} NMR spectroscopy and microanalysis. The structures of the distorted octahedral chelate complexes [TeX₄{RS(CH₂)₂SR}] (X = Cl or Br; R = Me or ⁱPr) and the centrosymmetric halo-bridged dimers [{X₃(Me₂S)Te}₂(μ-X)₂] (X = Cl or Br) involving Te(IV) are reported and the structures interpreted in terms of a three-centre-four-electron bonding model, with weak, secondary Te–S interactions. The structure of a unique Te(II) thioether complex, [TeCl{ⁱPrS(CH₂)₂SⁱPr}][Te₂Cl₉] obtained as a decomposition product from a sample of [TeCl₄{ⁱPrS(CH₂)₂SⁱPr}], in which a Te(II) thioether cation and Te(IV) chloride anion are weakly associated viaμ₂- and μ₃-bridging Cl ligands, is also described. In this case distortions in the coordination environment at the Te(II) ion are attributed to the effects of the Te-based lone pairs.