Tetraphenylphosphonium chloride

Tetraphenylphosphonium chloride

Names
IUPAC name Tetraphenylphosphonium chloride
Identifiers
CAS Number	2001-45-8
ChEMBL	ChEMBL223885
ChemSpider	144578
Jmol 3D model	Interactive image
PubChem	164911
InChI InChI=1S/C24H20P.ClH/c1-5-13-21(14-6-1)25(22-15-7-2-8-16-22,23-17-9-3-10-18-23)24-19-11-4-12-20-24;/h1-20H;1H/q+1;/p-1 Key: WAGFXJQAIZNSEQ-UHFFFAOYSA-M InChI=1S/C24H20P.ClH/c1-5-13-21(14-6-1)25(22-15-7-2-8-16-22,23-17-9-3-10-18-23)24-19-11-4-12-20-24;/h1-20H;1H/q+1;/p-1 Key: WAGFXJQAIZNSEQ-REWHXWOFAO Key: WAGFXJQAIZNSEQ-UHFFFAOYSA-M
SMILES [Cl-].c1c(cccc1)[P+](c2ccccc2)(c3ccccc3)c4ccccc4
Properties
Chemical formula	C24H20ClP
Molar mass	374.84 g/mol
Appearance	colourless solid
Density	1.27 g dm^−3
Melting point	272 to 274 °C (522 to 525 °F; 545 to 547 K)
Hazards
R-phrases	36/37/38
S-phrases	26-36
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

Tetraphenylphosphonium chloride is the chemical compound with the formula (C₆H₅)₄PCl, abbreviated Ph₄PCl or PPh₄Cl. Tetraphenylphosphonium and especially tetraphenylarsonium salts were formerly of interest in gravimetric analysis of perchlorate and related oxyanions. This colourless salt is used to generate lipophilic salts from inorganic and organometallic anions. Thus, Ph₄P⁺ is useful as a phase-transfer catalyst, again because it allows inorganic anions to dissolve in organic solvents.

Structure and basic properties

The cation is tetrahedral. PPh₄Cl crystallises as the anhydrous salt,^[1] which is normal item of commerce, as well as a monohydrate^[2] and a dihydrate.^[3]

In X-ray crystallography, PPh+
4 salts are of interest as they often crystallise easily. The rigidity of the phenyl groups facilitates packing and elevates the melting point relative to alkyl-based quaternary ammonium salts. Also, since these salts are soluble in organic media, a wide range of solvents can be employed for their crystallisation.

constituent ions in the solid	space-filling model of part of the crystal structure	ball-and-stick model of part of the crystal structure

Preparation

PPh₄Cl and many analogous compounds can be prepared by the reaction of chlorobenzene with triphenylphosphine catalysed by nickel salts:^[4]

PhCl + PPh₃ → Ph₄PCl

The compound was originally prepared as the corresponding bromide salt (CAS No. 2751-90-8), which in turn was synthesized by passing dry oxygen through the reaction of phenylmagnesium bromide and triphenylphosphine.^[5] The synthesis probably proceeds via the reaction of the Grignard reagent with triphenylphosphine oxide.

PhMgBr + Ph₃PO → Ph₄POMgBr

Ph₄POMgBr + HBr → Ph₄PBr + "Mg(OH)Br"

References

1. Richardson, J. F.; Ball, J. M.; Boorman, P. M. (1986). "Structure of Tetraphenylphosphonium Chloride". Acta Crystallographica C42: 1271–1272. doi:10.1107/S0108270186092612.
2. Schweizer, E. E.; Baldacchini, C. J.; Rheingold, A. L. (1989). "Tetraphenylphosphonium Chloride Monohydrate, Tetraphenylphosphonium Bromide and Tetraphenylphosphonium Iodide". Acta Crystallographica C45: 1236–1239. doi:10.1107/S0108270189000363.
3. Blake, A. J.; Garner, C. D.; Tunney, J. M. (2003). "Tetraphenylphosphonium Chloride Dihydrate". Acta Crystallographica E59: o9–o10. doi:10.1107/S1600536802021682.
4. Marcoux, David; Charette, André B. (2008). "Nickel-Catalyzed Synthesis of Phosphonium Salts from Aryl Halides and Triphenylphosphine". Adv. Synth. Catal. 350: 2967–2974. doi:10.1002/adsc.200800542.
5. Dodonow, J.; Medox, H. (1928). "Zur Kenntnis der Grignardschen Reaktion: Über die Darstellung von Tetraphenyl-phosphoniumsalzen". Berichte der deutschen chemischen Gesellschaft 61: 907–911. doi:10.1002/cber.19280610505.