“…In recent years, electron-rich carbon-based substituents like (pentamethyl)cyclopentadienyl or ferrocenyl groups have been employed to tame the reactivity of phosphenium ions, ,, and only very recently, a donor-free, exclusively kinetically stabilized phosphenium ion was isolated by Beckmann et al Non-stabilized, in situ formed phosphenium ions are attractive species, e.g., as building blocks for polyphosphorus compounds, for small molecule activation, , or their ability to act as dienophiles toward 1,3-dienes …”