Upon electron ionization of phenylphosphine (M=110) there are three ions observed in the mass spectrum – m/z 107 and m/z 108 (most abundant) and m/z 109. The structures of these ions have attracted attention in the past and structures for m/z 108 and m/z 109 have been discussed briefly, but no suggestions for the structure of m/z 107 have been made. We have proposed a structure for the ion of m/z 107 as being a phosphenium ion. Also we have attempted to clarify the existence of the phosphatropylium ion m/z 109 as an alternative to the PhPH⁺.

Phosphenium ions are charged electron-deficient reactive intermediates having six valence electrons - analogs of carbenes. The ions of m/z 107 and m/z 109 have been investigated by a combination of reactivity studies of their addition reaction and electronic structure calculations.