nitrilium betaines

Derivatives of nitriles having the general structure R–C≡N+–Y. A subclass of 1,3-dipolar compounds including nitrile imides, nitrile oxides, nitrile sulfides and nitrile ylides.
Source:
PAC, 1995, 67, 1307 (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1351