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PCl5

Phosphorus pentachloride
Phosphorus pentachloride (gas phase structure)
Phosphorus pentachloride
Phosphorus-pentachloride-3D-vdW.png
Phosphorus pentachloride ampoule.jpg
Names
IUPAC names
Phosphorus pentachloride
Phosphorus(V) chloride
Other names
Pentachlorophosphorane
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.030.043
EC Number 233-060-3
PubChem CID
RTECS number TB6125000
UNII
UN number 1806
Properties
Cl5P
Molar mass 208.22 g·mol−1
Appearance colourless crystals
Odor pungent, unpleasant
Density 2.1 g/cm3
Melting point 160.5 °C (320.9 °F; 433.6 K)
Boiling point 166.8 °C (332.2 °F; 439.9 K) sublimation
decomposition
(exothermic)
Solubility soluble in CS2, chlorocarbons, benzene
Vapor pressure 1.11 kPa (80 °C)
4.58 kPa (100 °C)
Structure
tetragonal
D3h (trigonal bipyramidal)
0 D
Thermochemistry
111.5 J/mol·K
364.2 J/mol·K
Hazards
Safety data sheet ICSC 0544
GHS pictograms The corrosion pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)The skull-and-crossbones pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)The health hazard pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Danger
H302, H314, H330, H373
P260, P280, P284, P305+351+338, P310
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazard W: Reacts with water in an unusual or dangerous manner. E.g., cesium, sodiumNFPA 704 four-colored diamond
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (median dose)
 660 mg/kg (rat, oral)
205 mg/m3 (rat)
1020 mg/m3 (mouse, 10 min)
US health exposure limits (NIOSH):
PEL (Permissible)
 TWA 1 mg/m3
REL (Recommended)
 TWA 1 mg/m3
IDLH (Immediate danger)
 70 mg/m3
Related compounds
Related phosphorus pentahalides
 Phosphorus pentafluoride
Phosphorus pentabromide
Phosphorus pentaiodide
Related compounds
 Phosphorus trichloride
Phosphoryl chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Phosphorus pentachloride is the chemical compound with the formula PCl5. It is one of the most important phosphorus chlorides, others being PCl3 and POCl3. PCl5 finds use as a chlorinating reagent. It is a colourless, water- and moisture-sensitive solid, although commercial samples can be yellowish and contaminated with hydrogen chloride.

The structures for the phosphorus chlorides are invariably consistent with VSEPR theory. The structure of PCl5 depends on its environment. Gaseous and molten PCl5 is a neutral molecule with trigonal bipyramidal (D3h) symmetry. The hypervalent nature of this species (as well as for PCl−
6, see below) can be explained with the inclusion of non-bonding MOs (Molecular orbital theory) or resonance (Valence bond theory). This trigonal bipyramidal structure persists in non-polar solvents, such as CS2 and CCl4. In the solid state PCl5 is ionic, formulated PCl+
4PCl−
6.

In solutions of polar solvents, PCl5 undergoes "autoionization". Dilute solutions dissociate according to the following equilibrium:

At higher concentrations, a second equilibrium becomes more prevalent:

The cation PCl+
4 and the anion PCl−
6 are tetrahedral and octahedral, respectively. At one time, PCl5 in solution was thought to form a dimeric structure, P2Cl10, but this suggestion is not supported by Raman spectroscopic measurements.


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