“…During the past three decades, researchers have sought other, all-inorganic, aromatic species. For example, N 2 S 3 2+ , 20 N 3 S 2 + , 21 and SN 2 P 2 , 22 which are isolobal to cyclo -P 5 – , have been identified; but N 2 S 3 2+ is not stable in solutions (N 2 S 3 2+ ), SN 2 P 2 is only stable when isolated in an Ar matrix, and only N 3 S 2 + has proven to be stable enough for isolation. Cyclo -N 5 – , the first-row congener of cyclo -P 5 – , has only been observed in the gas phase, where it can be formed via collision induced dissociation (CID) of a compound containing the N 5 unit 23 , 24 or its presence inferred via labeling studies of azide ion produced in the decomposition.…”