It is a colourless, water-sensitive solid, although commercial samples can be yellowish and contaminated with hydrogen chloride.

[5] In the solid state PCl5 is an ionic compound called tetrachlorophosphonium hexachlorophosphate formulated PCl+4PCl−6.

At one time, PCl5 in solution was thought to form a dimeric structure, P2Cl10, but this suggestion is not supported by Raman spectroscopic measurements.

[9] At low temperatures, SbCl5 converts to the dimer, dioctahedral Sb2Cl10, structurally related to niobium pentachloride.

In its most characteristic reaction, PCl5 reacts upon contact with water to release hydrogen chloride and give phosphorus oxides.

Thionyl chloride is more commonly used in the laboratory because the resultant sulfur dioxide is more easily separated from the organic products than is POCl3.

PCl5 reacts with a tertiary amides, such as dimethylformamide (DMF), to give dimethylchloromethyleneammonium chloride, which is called the Vilsmeier reagent, [(CH3)2N=CClH]Cl.

For oxidative chlorinations on the laboratory scale, sulfuryl chloride is often preferred over PCl5 since the gaseous SO2 by-product is readily separated.

The reaction of phosphorus pentoxide and PCl5 produces POCl3 :[18][page needed] PCl5 chlorinates nitrogen dioxide to form unstable nitryl chloride: PCl5 is a precursor for lithium hexafluorophosphate, LiPF6.