Ylide

An ylide or ylid (/ˈɪlɪd/ or /ˈɪlaɪd/) is a neutral dipolar molecule containing a formally negatively charged atom (usually a carbanion) directly attached to a heteroatom with a formal positive charge (usually nitrogen, phosphorus or sulfur), and in which both atoms have full octets of electrons. Ylides are thus 1,2-dipolar compounds. They appear in organic chemistry as reagents or reactive intermediates.