The air-stable phosphorane (2-oxo-2-phenyltriphenylphosphoniumethylide
) is shown to be a resonance hybrid of an ylene, ylidic and enolate ca
nonical assembly. The geometry around the P atom is nearly tetrahedral
. The O atom is oriented cis to the P atom. The phenyl ring of the ben
zoyl group is twisted with respect to the plane containing the carbony
l group.