https://en.wikipedia.org/wiki/Hexanitrogen

Hexanitrogen (diazide, hexaaza-1,2,4,5-tetraene) is an allotrope of nitrogen with the formula N6. The six nitrogen atoms are all covalently bonded in a single molecule: two azide units linked to each other. Its stability and structure were theorized in 2016 and its synthesis was reported in 2025. It is stable at cryogenic temperatures.