Organomercury(II) and tellurium(II) compounds with the "pincer" ligand 2,6-[O(CH2CH2)2NCH2]2C6H3 - stabilization of an unusual organotellurium(II) cationic species

The reaction of RH (1) with Hg(OAc)(2), in EtOH, gave the acetate RHgOAc (2) [R= 2,6-[O(CH2CH2)(2)NCH2](2)C6H3]. The corresponding RHgCl (3) was obtained from 2 and LiCl. The reaction of 3 with TeCl4 (1 : 1 molar ratio), in anhydrous 1,4-dioxane, resulted in the transfer of the organic ligand from mercury to tellurium and the isolation of the unexpected ionic compounds [RTe](2)[Hg2Cl6] (4) and [RH3][HgCl4] (5). The molecular structures of 1-4 and 5 center dot H2O were established by single-crystal X-ray diffraction. The acetate 2 and the chloride 3 are monomeric in solid state. In both mercury and tellurium organometallic compounds the organic group acts as an (N, C, N) "pincer" ligand. This coordination pattern provided stability for the rare [RTe](+) cation. Weak cation-anion interactions [Te...Cl 3.869(3) angstrom] are present between [RTe](+) and the dinuclear anion [Hg2Cl6](2-) in the crystal of 4. Theoretical calculations with DFT methods were performed for models of 3 and 4. The results show that in the cation of 4 the coordination of the nitrogen atoms play an important role for the stabilization of the structure found in the crystal whereas in 3 the coordination of the nitrogen atoms to the metal centre stabilizes to a less extent the structure found in solid state.