The crystal and molecular structure of benzoyl-pentafluoropropionylmethylene triphenylarsorane

Abstract

Benzoyl-pentafluoropropionylmethylene triphenylarsorane contains two strongly electron-withdrawing groups in alkylidene moiety. Single crystals obtained from CH3OH-H2O solution are triclinic, the space group is , with a = 12.292A, b = 13.457A, c = 15.318A, α = 90.562° β = 90.516°, γ = 92.820°, and Z = 4. The X-ray diffraction intensity data were collected with a four-circle diffractometer. The structure has been solved by heavy-atom method and refined by block-diagonal least-squares method. The final R was 0.061 for 8393 independent observed reflections. The ylide carbon is planar sp2 hybridized. The bond length of As-Cylide is 1.888A, much longer than As = C, and also longer than the corresponding bond length in other arsonium ylides previously reported, indicating a smaller contribution of “double bond” canonical form to the overall structure. On the other hand, the easier delocalization of negative charge due to the two strongly electron-withdrawing groups results in the greater chemical stability.