text: Certain nitrogen-based ylides also exist such as azomethine ylides with the general structure:
  These compounds can be envisioned as iminium cations placed next to a carbanion. The substituents R, R are electron withdrawing groups. These ylides can be generated by condensation of an α-amino acid and an aldehyde or by thermal ring opening reaction of certain N-substituted aziridines. 
  The further-unsaturated nitrile ylides are known almost exclusively as unstable intermediates.  
  A rather exotic family of dinitrogen-based ylides are the isodiazenes (RRN=N), which generally decompose by extrusion of dinitrogen.
  Stable carbenes also have a ylidic resonance contributor, e.g.: