An experimental and theoretical investigation on hypervalent organoselenium(II) halides: Case study of [2-(Et2NCH2)C6H4]SeX (X = Cl, Br, I)

Cleavage of the Se–Se bond in [2-(Et2NCH2)C6H4]2Se2 (1) with SO2Cl2 (1:1 molar ratio) yielded the organoselenium(II) chloride [2-(Et2NCH2)C6H4]SeCl (2). Treatment of 2 with excess of KX yielded the organoselenium(II) halides [2-(Et2NCH2)C6H4]SeX [X = Br (3), I (4)]. The new compounds 2–4 were characterized by solution NMR spectroscopy (1H, 13C, 77Se, 2D experiments). The solid-state molecular structures of 2, 2·HCl and 3 were established by single crystal X-ray diffraction. Distorted T-shaped coordination geometries of type (C,N)SeX (X = Cl, Br) and CSeCl2 were found for the neutral halides 2 and 3, and the zwitterionic species [2-{Et2N+(H)CH2}C6H4]SeCl2‾ (2·HCl), respectively. DFT calculations were performed on 2–4 and the related tellurium compounds [2-(Et2NCH2)C6H4]TeX [X = Cl (5), Br (6) and I (7)] in order to elucidate the bond nature and FT-Raman features of this class of organochalcogen(II) derivatives.

The arylselenium(II) compounds [2-(Et2NCH2)C6H4]SeX [X = Cl (2), Br (3), I (4)] were synthesized and structurally characterized. Their solid state structures with a distorted T-shaped (C,N)SeX (X = Cl, Br) coordination geometry resemble those of the analogous hypervalent halides with 2-(Me2NCH2)C6H4 groups. The structure of the zwitterionic species [2-{Et2N+(H)CH2}C6H4]SeCl2− (2·HCl) with a T-shaped CSeCl2 core was also determined. NMR spectra revealed the presence of internal nitrogen-selenium coordination in solution too. DFT calculations allowed the investigation of the nature of the chemical bond in the title compounds and their vibrational properties.Figure optionsDownload as PowerPoint slideHighlights
► Hypervalent [2-(Et2NCH2)C6H4]SeX (X = Cl, Br, I) were obtained and characterized.
► R.t. 1H and 77Se NMR spectra provided evidences for internal N → Se coordination.
► Distorted T-shaped (C,N)SeX core as result of strong internal N → Se interaction.
► zwitterionic [2-{Et2N+(H)CH2}C6H4]SeCl2‾ with a distorted T-shaped CSeCl2 core.
► DFT calculations suggest polarised 3c–4e nature for the N → E–X systems (E = Se, Te).