Tellurated heterocycles, 2-[(2-thienyltelluro)methyl]tetrahydrofuran (L1) and [(2-thienyltelluro)methyl]tetrahydro-2H-pyran (L2): Synthesis and complexation reactions with Pd(II), Pt(II), Hg(II), Ru(II) and Cu(I): Single crystal structures of [Ru(p-cymene

2-Thienyllithium (ThLi) reacts with elemental Te to give ThTeLi which on reaction with tetrahydrofurfurylchloride and 2-(bromomethyl)tetrahydro-2H-pyran at −78 °C results in L1 and L2. Their complexes [PdCl2(L1)2] (1), [PtCl2(L1)2] (2), [HgBr2(L1)2] (3), [Ru(p-cymene)Cl2(L1)] (4), [CuBr(L1)] (5), [PdCl2(L2)2] (6), [PtCl2(L2)2] (7), [HgBr2(L2)2] (8) and [Ru(p-cymene)Cl2(L2)] (9). Both the ligands and all nine complexes have characteristic 1H and 13C NMR spectra which reveal that in most of the complexes the two ligands L1 and L2 coordinate through Te only. This is corroborated by single crystal structures of 4 and 6. The 4 is a half sandwich compound, in which co-ligands of p-cymene are Cl and L1 (monodentate coordinated through Te). The Ru–Te bond length is 2.6340(7) Å. In the 6 Pd has nearly square planar geometry and molecules of ligand L2 are cis to each other, which is something rare with the monodentate telluride ligands. The Pd–Te bond lengths are 2.538(2) and 2.517(2) Å. The crystal structure of 6 also shows presence of secondary Te⋯Cl interactions in the crystal lattice. The Pd–Pd distance in 6 becomes 3.188(3) Å, less than 3.26 Å (sum of vander Waal’s radii). The ligation of L1 and L2 is compared with those of related ligands.