The crystal structure of the third isomer of cyclooctenobis-1,2,3-selenadiazoles, C8H8N4Se2, is reported. The mol-ecule is located on a twofold rotation axis. The eight-membered ring adopts a twist-chair conformation with planar heterocycles. C-H⋯N hy-dro-gen bonds connect the mol-ecules into layers parallel to (101).
Detert et al. (Fri,) studied this question.