@C00806@, derived by formal @I03058@ of a divalent carbon atom into an even-membered @A00368@, e.g. cycloheptatrienylidene:
A00369.png
Source: PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1318 [Terms] [Paper]