Differences Between Gas-Phase and Solid-State Molecular Structures of the Simplest Phosphonium Ylide, Me P=CH.

Clearly different from local C symmetric is the heavy-atom core of Me P=CH , the simplest phosphonium ylide. The geometry obtained by reanalysis of gas-electron-diffraction data from 1977 is now consistent with theoretical calculations, but different from the molecular structure in the solid state. The picture shows the structure of Me P=CH in the gas phase (a) and in the crystal (c) together with the calculated transition state (b) (viewed along the P=C bond).