phosphonium ylide
phosphonium ylide
Compounds having the structure R<small><sub>3</sub></small>P<small><sup>+</small></sup>‒C<small><sup>−</small></sup>R<small><sub>2</sub></small> ↔ R<small><sub>3</sub></small>P=CR<small><sub>2</sub></small>, where the phosphorus atom is bonded to four separate atoms.