| Popis: |
The transmetalation reactions of a mercury precursor, [(Pentyl)(NCN)HgCl] (19), with selenium halides (SeCl4, SeBr4, and SeCl2) were attempted to obtain the corresponding organoselenium trichloride [(Pentyl)(NCN)SeCl3], tribromide [(Pentyl)(NCN)SeBr3], and monochloride [(Pentyl)(NCN)SeCl], respectively [(NCN) = 5-tert-butyl-1,3-bis-(N-pentyl-benzimidazol-2'-yl)phenyl]. However, in all the cases, a very facile ionization of the Se-halogen bond was observed leading to the isolation of a new class of air stable arylselenium(II) complexes: [(Pentyl)(NCN)Se+](2)[HgCl4](2-) (20) and [(Pentyl)(NCN)Se+](2)[HgBr4](2-) (21). This is the first report on the formation of NCN pincer-based arylselenium(II) cations via the transmetalation route. Similar reactions were further investigated with several tellurium precursors: {TeCl4, TeBr4 and TeI2} which resulted in the formation of analogous aryltellurium(II) complexes: [(Pentyl)(NCN)Te+](2)[HgCl4](2) (22), [(Pentyl)(NCN)Te+][Cl](-) (23), [(Pentyl)(NCN)Te+](2)[HgBr4](2-) (24), [(Pentyl)(NCN)Te+][Br](-) (25) and [(Pentyl)(NCN)Te+](4)[Hg2Cl4.72I3.28](4-) (26). These are only the second set of examples of aryltellurium cations (hypervalent 10-Te-3 species) with the NCN pincer-based ligand, characterised by X-ray crystallographic studies. The crystallographic studies show a strong Se center dot center dot center dot N/Te center dot center dot center dot N intramolecular interaction, which is confirmed by NBO calculations suggesting the donation of a lone pair of electrons on nitrogen to a lone p-vacancy on selenium/tellurium atoms. The analysis based on NPA derived charges indicates that the contribution of Se center dot center dot center dot N interactions to the electrostatic stabilization energy is in the range of 40 60%, whereas Te center dot center dot center dot N interactions have a contribution of about 84% and more, attributed to the differences in the electronegativity of selenium and tellurium. Furthermore, the formation of arylselenium(II) and aryltellurium(II) complexes was favoured due to the presence of the s-hole on the Se/Te centres. |
