Solid phosphorus pentachloride is an ionic compound, formulated , that is, a salt containing the tetrachlorophosphonium cation. Dilute solutions dissociate according to the following equilibrium:
:PCl   + Cl
Triphenylphosphine dichloride (PhPCl) exists both as the pentacoordinate phosphorane and as the chlorotriphenylphosphonium chloride, depending on the medium. The situation is similar to that of PCl. It is an ionic compound (PPhCl)Cl in polar solutions and a molecular species with trigonal bipyramidal molecular geometry in apolar solution.