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Triphenylphosphine oxide

Triphenylphosphine oxide
Systematic name Triphenylphosphine oxide
Other names  ?
Molecular formula C18H15OP
SMILES O=P(c1ccccc1)-
Molar mass 278.28 g/mol
Appearance white crystals
CAS number [791-28-6]
Density and phase  ? g/cm3, solid
Solubility in water low
Other solvents polar organic solvents
Melting point 154-158 °C (427-429 K)
Boiling point 360 °C (633 K)
Acidity (pKa)  ?
Molecular shape tetrahedral
Dipole moment  ? D
MSDS External MSDS
Main hazards slight
NFPA 704
R/S statement R: 22-36/37/38
S: 26
RTECS number SZ1676000
Supplementary data page
Structure and
n, εr, etc.
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Related compounds
Related compounds POCl3,
Except where noted otherwise, data are given for
materials in their standard state (at 25°C, 100 kPa)
Infobox disclaimer and references

Triphenylphosphine oxide is the chemical compound with the formula OP(C6H5)3. Often chemists abbreviate the formula by writing Ph3PO or PPh3O (Ph = C6H5). This white crystalline compound is a common side product in reactions involving triphenylphosphine. It is a popular reagent to induce the crystallizing of chemical compounds.

Additional recommended knowledge


Structure and properties

Ph3PO is tetrahedral molecule related to POCl3.[1] The oxygen center is relatively basic. The rigidity of the backbone and the basicity of the oxygen center make this species a popular agent to crystallize otherwise difficult to crystallize molecules. This trick is applicable to molecules that have acidic hydrogen atoms, e.g. phenols.[2]

As a by-product of organic synthesis

Ph3PO is a by-product of many useful reactions in organic synthesis including the Wittig, Staudinger, and Mitsunobu reactions. It is also formed when PPh3Cl2 is employed to convert alcohols into alkyl chlorides.

Ph3PCl2 + ROH → Ph3PO + HCl + RCl

Triphenylphosphine can be regenerated from the oxide by treatment with trichlorosilane.

Ph3PO + SiHCl3 → PPh3 + 1/n (OSiCl2)n + HCl

Coordination chemistry

Ph3PO is an excellent ligand for "hard" metal centers. A typical complex is the tetrahedral species NiCl2(OPPh3)2.[3]

Ph3PO is a common impurity in PPh3. The oxidation of PPh3 by oxygen, including air, is catalyzed by many metal ions:

2 PPh3 + O2 → 2 Ph3PO


  1. ^ D. E. C. Corbridge "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam. ISBN 0-444-89307-5.
  2. ^ M. C. Etter and P. W. Baures (1988). "Triphenylphosphine oxide as a crystallization aid". J. Am. Chem. Soc. 110 (2): 639-640. doi:10.1021/ja00210a076.
  3. ^ D. M. L. Goodgame and M. Goodgame (1965). "Near-Infrared Spectra of Some Pseudotetrahedral Complexes of Cobalt (II) and Nickel(II)". Inorg. Chem. 4 (2): 139-143. doi:10.1021/ic50024a002.

Other reading

  • Triphenylphosphine oxide at
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Triphenylphosphine_oxide". A list of authors is available in Wikipedia.
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