1-Ethylthio-2-[2-thienyltelluro]ethane (L) a new (Te, S) ligand: Synthesis and complexation with Ag(I), Cu(I), Pd(II) and Pt(II) – Single crystal structures of [PdCl2(L)] and bis(thienyl) tellurium(IV) chloride

Lithium 2-thienyltellurolate, generated from 2-thienyl lithium, reacts at −78 °C in THF with chloroethyl ethyl sulfide to give a (Te, S) ligand 1-ethylthio-2-[2-thienyltelluro]ethane (L) as a red oil. The complexes [PdCl2(L)] (1), [PtCl2(L)] (2), [Ag(L)2][ClO4] (3) and [CuBr(L)]2 (4) were synthesized. The complex [HgCl2(L)] on crystallization decomposed giving Th2TeCl2 (5) [where Th = 2-thienyl], which was characterized by X-ray diffraction on its single crystals. The ligand L and complexes 1–4 exhibit proton and carbon-13 NMR spectra, which are characteristic. The coordination through Te in 1–4 is indicated by downfield coordination shifts in the position of the TeCH2 signal of L. Complex 1 was characterized by X-ray diffraction on its single crystals. The geometry around Pd is square planar. The Pd–Te, Pd–S and Pd–Cl bond lengths are 2.5040(4), 2.273(1) and 2.322(1)/2.380(1) Å, respectively. There are intermolecular interactions between Te (coordinated to Pd) and Cl, and sulfur and Cl. The Te–Cl and S–Cl distances, 3.401 and 3.488 Å, respectively, are shorter than the sum of the van der Waal’s radii (3.81 and 3.55 Å, respectively). The Pd–Pd distance between the two molecules is 3.4156(6) Å, greater than the sum of van der Waal’s radii (3.26 Å). The structure of 5 is typical of that of a tellurium(IV) compound (saw-horse type). The two Te–Cl bond lengths are identical, 2.480(1) Å. The geometry around Te in 5 can be best described as pseudo tetrahedral (trigonal bipyramidal with a lone pair on one corner of the triangle).

Graphical abstract1-Ethylthio-2-[2-thienyltelluro]ethane(L) and its complexes [PdCl2(L)] (1), [PtCl2(L)] (2), [Ag (L)2][ClO4] (3) and [CuBr(L)]2 (4) were synthesized. [HgCl2(L)] on crystallization decomposes giving Th2TeCl2 (5) [Th = 2-thienyl]. L and 1–4 exhibit characteristic 1H and 13C NMR spectra. Single crystal structures of 1 and 5 were solved. The Pd–Te, Pd–S and Pd–Cl bond lengths are 2.5040(4), 2.273(1) and 2.322(1)/2.380(1) Å, respectively, in square planar 1. Intermolecular weak interactions exist in 1 between Te/S and Cl [Te–Cl/S–Cl 3.401/3.488 Å]. Complex 5 has a saw-horse type structure [Te–Cl, 2.480(1) Å].Figure optionsDownload full-size imageDownload as PowerPoint slide