'P' undressed: A stable phosphanylidene phosphorane with a sterically accessible (naked) two‐coordinate P is reported (see structure). Coordination to Pd⁰ reveals its phosphine donor/phosphinidene acceptor (R₃P→PR′) nature by exposing its phosphinidene‐like reactivity.

The effect of the special peri-geometry of rigid naphthalene-1,8-diyl backbone in phosphenium formation reaction was investigated. 1,8-Bis(diphenylphosphino) naphthalene and P₂I₄ afforded triphosphenium iodide in a clean reaction. The reaction of 1,8-bis(dimethylaminophosphino) naphthalene with P₂I₄ is complex, it afforded four products, all containing the 1,2-dihydro-1,2-diphosphaacenaphthylene motif and heterophosphonium functionalities. Two examples of the rare structural motif of two acenaphthylene units connected head to head and thus a contiguous chain of four phosphorus atoms were also isolated, one compound showing diastereomerization in the solution. All new compounds were fully characterised including single crystal X-ray diffraction.