Kation '''pentazolium''' siklik ({{chem|N|5|+}}) tidak diketahui karena kemungkinan sifat antiaromatiknya;
sedangkan kation [[pentazenium]] yang berantai terbuka ({{chem|N|5|+}}) diketahui. Butler dkk. pertama membuktikan adanya siklik {{chem|N|5|-}} dalam larutan melalui penguraian aril pentazol tersubstitusi pada suhu rendah. Kehadiran {{chem|N|5|H|}} dan {{chem|N|5|-}} (dalamditahan bentukdalam larutan melalui interaksi dengan ion seng) terbukti terutama menggunakan teknik produk penguraian <sup>15</sup>N NMR teknik produk penguraian.<ref>{{Cite journal| url = http://www.rsc.org/delivery/_ArticleLinking/DisplayHTMLArticleforfree.cfm?JournalCode=CC&Year=2003&ManuscriptID=b301491f&Iss=8 | doi = 10.1039/b301491f| title = First generation of pentazole (HN5, pentazolic acid), the final azole, and a zinc pentazolate salt in solution: A new N-dearylation of 1-(p-methoxyphenyl) pyrazoles, a 2-(p-methoxyphenyl) tetrazole and application of the methodology to 1-(p-methoxyphenyl) pentazole | journal = Chemical Communications| issue = 8| pages = 1016| year = 2003| last1 = Butler| first1 = R. N.| last2 = Stephens| first2 = John C.| last3 = Burke| first3 = Luke A.}}</ref>
