ELECTRON-DISTRIBUTION IN TERT-BUTYL PHOSPHAETHYNE BU(T)C-P

The first high-precision, low-temperature, X-ray diffraction study on a phosphaalkyne reveals that the lone pair electrons are located much closer to the P atom than in the related phosphaalkene, and furthermor e there is a significant excess electron density on the sp-hybridised C atom, thus readily accounting for the remarkable preferential proton ation at C rather than at P in spite of the presence of the lone-pair electrons.