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Synthesis and Structure of Arylselenenium(II) and Aryltellurenium(II) Cations Based on Rigid 5-tert-Butyl-1,3-bis-(N-pentylbenzimidazol-2'-yl)benzenes

Abstract

The transmetalation reactions of mercury precursor, [Pentyl(N^C^N)HgCl] (19) with selenium halides (SeCl4, SeBr4, and SeCl2) were attempted to obtain the corresponding organoselenenium trichloride [Pentyl(N^C^N)SeCl3], tribromide [Pentyl(N^C^N)SeBr3], and monochloride [Pentyl(N^C^N)SeCl] respectively [(N^C^N) = 5-tert-butyl-1,3-bis-(N-pentyl-benzimidazol-2'yl)phenyl]. However, in all the cases 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(N^C^N)Se+]2[HgCl4]2-(20), [Pentyl(N^C^N)Se+]2[HgBr4]2- (21). This is the first report on the formation of NCN pincer based arylselenenium(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(N^C^N)Te+]2[HgCl4]2-(22), [Pentyl(N^C^N)Te+][Cl]- (23), [Pentyl(N^C^N)Te+]2[HgBr4]2- (24), [Pentyl(N^C^N)Te+][Br]- (25) and [Pentyl(N^C^N)Te+]4[Hg2Cl4.72I3.28]4- (26). These are only the second set of examples of aryltellurenium 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•••N/Te•••N intramolecular interaction, which is confirmed by NBO calculations suggesting the donation of lone pair of on nitrogen to lone p-vacancy on selenium/tellurium atoms. Analysis based on NPA derived charges indicate that the contribution of Se⸱⸱⸱N interactions to the electrostatic stabilization energy is in the range of 40-60% whereas Te•••N interactions have contribution of about 84% and more, attributed to differences in the electronegativity of selenium and tellurium. Further, the formation of arylselenium(II) and aryltellurium(II) complexes were favoured due to the presence of the σ-hole on the Se/Te centres.

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Publication details

The article was received on 25 Mar 2018, accepted on 08 Jun 2018 and first published on 11 Jun 2018


Article type: Paper
DOI: 10.1039/C8DT01148F
Citation: Dalton Trans., 2018, Accepted Manuscript
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    Synthesis and Structure of Arylselenenium(II) and Aryltellurenium(II) Cations Based on Rigid 5-tert-Butyl-1,3-bis-(N-pentylbenzimidazol-2'-yl)benzenes

    V. Rani, M. B, S. Raju, G. N. Patwari, H. B. Singh and R. J. Butcher, Dalton Trans., 2018, Accepted Manuscript , DOI: 10.1039/C8DT01148F

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