Relatively stable delocalized radicals, derived from hydrazyl,
H2NN·H, of the types shown, in particular the six-membered ring:
V06609.png
Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1374 (https://doi.org/10.1351/pac199567081307)