vinylidenes

https://doi.org/10.1351/goldbook.V06623
@C00806@ in which the carbenic carbon atom has a double bond to another carbon atom R2C=C:, e.g. H2C=C: ethenylidene.
Source:
PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1374 [Terms] [Paper]