LAUSR

Abstract In the area of polynitrogen anions, the only stable species synthesized as yet are the azide anion (N3−) and the pentazolate anion (cyclo-N5−). We here describe an unprecedented example of a spontaneous single-crystal to single-crystal transformation from the pentazolate salt [NH4]4[H3O]3(N5)6Cl to the known [NH4]N3 with concomitant release of N2 and H2O, which involves the cleavage of N–N bonds and a change in space group. This transformation is helpful for the understanding of the relationship between the long-known N3− and the recently synthesized cyclo-N5− polynitrogen anions.