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Phosphorus pentachloride is the chemical compound with the formula PCl 5. It is one of the most important phosphorus chlorides/oxychlorides, others being PCl 3 and POCl 3. PCl 5 finds use as a chlorinating reagent. It is a colourless, water-sensitive solid, although commercial samples can be yellowish and contaminated with hydrogen chloride.
Phosphorus pentachloride, phosphorus pentabromide, and phosphorus heptabromide are ionic in the solid and liquid states; PCl 5 is formulated as PCl 4 + PCl 6 –, but in contrast, PBr 5 is formulated as PBr 4 + Br −, and PBr 7 is formulated as PBr 4 + Br 3 −. They are widely used as chlorinating and brominating agents in organic chemistry.
Solid phosphorus pentachloride is an ionic compound, formulated [PCl 4] + [PCl 6] − (tetrachlorophosphonium hexachlorophosphate(V)), that is, a salt containing the tetrachlorophosphonium cation. [7] [8] Dilute solutions dissociate according to the following equilibrium: PCl 5 ⇌ PCl + 4 + Cl −
For example, both phosphorus oxychloride (POCl 3) and phosphorus pentachloride, (PCl 5) are neutral covalent compounds of phosphorus in the +5 oxidation state. If an oxygen atom is simply replaced by a halogen atom the charge increases by +1, but the coordination number is unchanged.
As examples, in PF 5 the axial P−F bond length is 158 pm and the equatorial is 152 pm, and in PCl 5 the axial and equatorial are 214 and 202 pm respectively. [ 2 ] In the mixed halide PF 3 Cl 2 the chlorines occupy two of the equatorial positions, [ 2 ] indicating that fluorine has a greater apicophilicity or tendency to occupy an axial position.
For example, in phosphorus pentafluoride (PF 5), 5 resonance structures can be generated each with four covalent bonds and one ionic bond with greater weight in the structures placing ionic character in the axial bonds, thus satisfying the octet rule and explaining both the observed trigonal bipyramidal molecular geometry and the fact that the ...
The pentachloride and pentafluoride are Lewis acids. With fluoride, PF 5 forms PF 6 −, an anion that is isoelectronic with SF 6. The most important oxyhalide is phosphorus oxychloride, (POCl 3), which is approximately tetrahedral. Before extensive computer calculations were feasible, it was thought that bonding in phosphorus(V) compounds ...
This is a list of common chemical compounds with chemical formulae and CAS numbers, indexed by formula. ... phosphorus difluoride: 13873-52-4 F 2 Pb: