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

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 SeN 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 center dot center dot center dot C interactions. In the crystal of the BBr3 derivative, the cooperative effect of Se center dot center dot center dot N chalcogen bonding and Br center dot center dot center dot 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 center dot center dot center dot Cl interactions resulting from the enhanced electrophilic character of the chalcogen atom.