Synthetic and structural investigations of bis( N -alkyl-benzoselenadiazolium) cations

The synthesis, and spectroscopic and structural characterization of bridged dicationic derivatives of benzo-2,1,3-selenadiazoles are reported. The chloride salt of [H₄C₆NSeN-CH₂-CH₂-NSeNC₆H₄]²⁺ crystallizes forming a macrocyclic structure in which two cations are bridged by SeCl chalcogen bonds (ChBs), with a third chloride at the centre of the macrocycle. The structure of [1,2-(H₄C₆NSeN)₂-C₆H₁₀]Cl₂ consists of two selenadiazolium cations linked by a chiral cyclohexane and capped by SeCl ChBs. Tetrafluoroborate salts of a xylene bridge crystallize in two pseudopolymorphs in which the cations form SeF ChBs in an anti- or syn-conformation. The triflate salt of ethylene-bridged cations dimerizes through the formation of the [Se-N]₂ supramolecular synthon with SeO ChBs capping the second selenium atom. In contrast, [H₄C₆NSeN-CH₂-CH₂-CH₂-NSeNC₆H₄](CF₃SO₃)₂ only forms SeO ChBs.