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 degrees 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 I 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) angstrom, 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 A, respectively, are shorter than the sum of the van der Waal's radii (3.81 and 3.55 A, respectively). The Pd-Pd distance between the two molecules is 3.4156(6) A, greater than the sum of van der Waal's radii (3.26 A). 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) A. 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).