Organomercury(II) and tellurium(II) compounds with the 'pincer' ligand 2,6-[O(CH_2CH_2)_2NCH_2] _2C_6H_3 - Stabilization of an unusual organotellurium(ii) cationic species

摘要

The reaction of RH (1) with Hg(OAc)_2, in EtOH, gave the acetate RHgOAc (2) [R = 2,6-[O(CH_2CH_2)_2NCH _2]_2C_6H_3]. The corresponding RHgCl (3) was obtained from 2 and LiCl. The reaction of 3 with TeCl_4 (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[Hg_2Cl_6] (4) and [RH _3][HgCl_4] (5). The molecular structures of 1-4 and 5·H_2O 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) ?] are present between [RTe]~+ and the dinuclear anion [Hg_2Cl_6]~(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.