Triphenylphosphine dichloride

Triphenylphosphine dichloride, (C6H5)3PCl2, is a chlorinating agent widely used in organic chemistry. Applications include the conversion of alcohols and ethers to alkyl chlorides, the cleavage of epoxides to vicinal dichlorides and the chlorination of carboxylic acids to acyl chlorides.[2]

Triphenylphosphine dichloride
Structural formula
Ball-and-stick model
Ball-and-stick model
Space-filling model
Space-filling model
Names
Preferred IUPAC name
Dichlorotri(phenyl)-λ5-phosphane
Other names
Dichlorotriphenylphosphorane
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.107.819
UNII
  • InChI=1S/C18H15Cl2P/c19-21(20,16-10-4-1-5-11-16,17-12-6-2-7-13-17)18-14-8-3-9-15-18/h1-15H ☒N
    Key: ASWXNYNXAOQCCD-UHFFFAOYSA-N ☒N
  • ClP(Cl)(c1ccccc1)(c1ccccc1)c1ccccc1
Properties
C18H15Cl2P
Molar mass 333.19 g/mol
Melting point 176 °C (349 °F; 449 K)[1] 85-100 °C[2]
Reacts
Related compounds
Related compounds
 Phosphoranes
Triphenylphosphine
Phosphorus trichloride
Phosphorus pentachloride
Phosphorus halides
Tetraphenylphosphonium 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

Structure

In polar solvents such as acetonitrile, Ph3PCl2 adopts an ionic phosphonium salt structure, [Ph3PCl+]Cl−,[3] whereas in non-polar solvents like diethyl ether it exists as a non-solvated trigonal bipyramidal molecule.[4] Two [Ph3PCl+] species can also adopt an unusual dinuclear ionic structure—both interacting with a Cl− via long Cl–Cl contacts.[3]

Synthesis

Triphenylphosphine dichloride is usually prepared fresh by the addition of chlorine to triphenylphosphine.

Ph3P + Cl2 → Ph3PCl2

Both reagents are typically used in solution to ensure the correct stoichiometry.[2]

Ph3PCl2 can also be obtained by the reaction of iodobenzene dichloride (PhICl2) and triphenylphosphine.[5]

Alternatively, Ph3PCl2 can be obtained by chlorination of triphenylphosphine oxide with, for example, phosphorus trichloride, as in Grignard's original 1931 synthesis.[1]

References
  1. Victor Grignard, J. Savard (1931). Comptes rendus de l'Académie des sciences. 192: 592–5. {{cite journal}}: Missing or empty |title= (help)
  2. e-EROS Encyclopedia of Reagents for Organic Synthesis, doi:10.1002/047084289X.rt371
  3. S. M. Godfrey; C. A. McAuliffe; R. G. Pritchard; J. M. Sheffield (1996). "An X-ray crystallorgraphic study of the reagent Ph3PCl2; not charge-transfer, R3P–Cl–Cl, trigonal bipyramidal or [R3PCl]Cl but an unusual dinuclear ionic species, [Ph3PCl+⋯Cl–⋯+CIPPH3]Cl containing long Cl–Cl contacts". Chemical Communications (22): 2521–2522. doi:10.1039/CC9960002521.
  4. S. M. Godfrey; C. A. McAuliffe; J. M. Sheffield (1998). "Structural dependence of the reagent Ph3PCl2 on the nature of the solvent, both in the solid state and in solution; X-ray crystal structure of trigonal bipyramidal Ph3PCl2, the first structurally characterised five-coordinate R3PCl2 compound". Chem. Commun. (8): 921–922. doi:10.1039/a800820e.
  5. Carle, M. S., Shimokura, G. K. and Murphy, G. K. (2016), Iodobenzene Dichloride in the Esterification and Amidation of Carboxylic Acids: In-Situ Synthesis of Ph3PCl2. Eur. J. Org. Chem., 2016: 3930–3933. {{DOI:10.1002/ejoc.201600714}}
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