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(CH(2)CH(2))(2)NCH(2)](2)C(6)H(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(2)Cl(6)] (4) and [RH(3)][HgCl(4)] (5). The molecular structures of 1-4 and 5·H(2)O 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) Å] are present between [RTe](+) and the dinuclear anion [Hg(2)Cl(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.

Solid state structure and solution behaviour of organoselenium(II) compounds containing 2-{E(CH2CH2)2NCH2}C6H4 groups (E = O, NMe).

Cleavage of the Se-Se bond in [2-{O(CH(2)CH(2))(2)NCH(2)}C(6)H(4)](2)Se(2) (1) and [2-{MeN(CH(2)CH(2))(2)NCH(2)}C(6)H(4)](2)Se(2) (2) by treatment with SO(2)Cl(2), bromine or iodine (1 : 1 molar ratio) yielded [2-{O(CH(2)CH(2))(2)NCH(2)}C(6)H(4)]SeX [X = Cl (3), Br (4), I (5)] and [2-{MeN(CH(2)CH(2))(2)NCH(2)}C(6)H(4)]SeI (6). The compounds were characterized in solution by NMR spectroscopy (1H, 13C, 15N, 77Se, 2D experiments). The solid-state molecular structures of 1-3, 4.HBr, 5 and 6 were established by single crystal X-ray diffraction. In all cases T-shaped coordination geometries, i.e. (C,N)SeSe (1, 2), (C,N)SeX (3, 5, 6; X = halogen) or CSeBr(2) (4.HBr), were found. Supramolecular associations in crystals based on hydrogen contacts are discussed.