Sigma-hole interactions in the molecular and crystal structures of N-boryl benzo-2,1,3-selenadiazoles

Abstract

N-Bonded adducts of benzo-2,1,3-selenadiazole with BX₃ (X = Ph, F, Cl, Br) were prepared and crystallographically characterized. The structures of the 1 : 1 adducts of BF₃ and BCl₃ demonstrate dimerization through the [Se–N]₂ supramolecular synthon and enhancement of the corresponding Se⋯N chalcogen bonding interactions. However, the structures of the BPh₃ and BBr₃ compounds indicate that other supramolecular interactions can efficiently compete and inhibit [Se–N]₂ dimerization. In the case of the BPh₃ adduct, dispersion favors a dimer featuring Se⋯C interactions. In the crystal of the BBr₃ derivative, the cooperative effect of Se⋯N chalcogen bonding and Br⋯Br halogen bonding interactions lead to a network structure. A 1 : 2 adduct could be isolated only in the case of BCl₃; its structure features short intramolecular Se⋯Cl interactions resulting from the enhanced electrophilic character of the chalcogen atom.