Triphenylphosphine oxide (often abbreviated TPPO) is the organophosphorus compound with the formula OP(C6H5)3, also written as Ph3PO or PPh3O (Ph = C6H5). It is one of the more common phosphine oxides. This colourless crystalline compound is a common but potentially useful waste product in reactions involving triphenylphosphine. It is a popular reagent to induce the crystallizing of chemical compounds.
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| Names | |
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| Preferred IUPAC name
Triphenyl-λ5-phosphanone | |
| Other names
Triphenylphosphine oxide
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| Identifiers | |
3D model (JSmol)
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| 745854 | |
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| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.011.217 |
| EC Number |
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| 6758 | |
PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| C18H15OP | |
| Molar mass | 278.29 g/mol |
| Appearance | white crystals |
| Density | 1.212g/cm^3 |
| Melting point | 154 to 158 °C (309 to 316 °F; 427 to 431 K) |
| Boiling point | 360 °C (680 °F; 633 K) |
| low | |
| Solubility in other solvents | polar organic solvents |
| Structure | |
| tetrahedral | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards
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slight |
| GHS labelling:[1] | |
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| Warning | |
| H302, H412 | |
| P261, P264, P270, P271, P273, P280, P301+P312, P302+P352, P304+P340, P305+P351+P338, P312, P330, P332+P313, P337+P313, P362, P403+P233, P405 | |
| Related compounds | |
Related compounds
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P(C6H5)3S; |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Structure and properties
editPh3PO is structurally related to POCl3.[2] As established by X-ray crystallography, the geometry around P is tetrahedral, and the P-O distance is 1.48 Å.[3] Other modifications of Ph3PO have been found: For example, a monoclinic form crystalizes in the space group P21/c with Z = 4 and a = 15.066(1) Å, b = 9.037(2) Å, c = 11.296(3) Å, and β = 98.47(1)°.The orthorhombic modification crystallizes in the space group Pbca with Z = 4 and 29.089(3) Å, b = 9.1347(9), c = 11.261(1) Å.[4]
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.[5]
As a byproduct of organic synthesis
editPh3PO is a byproduct 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 a variety of deoxygenation agents, such as phosgene or trichlorosilane/triethylamine:[6]
- Ph3PO + SiHCl3 → PPh3 + 1/n (OSiCl2)n + HCl
Triphenylphosphine oxide can be difficult to remove from reaction mixtures by means of chromatography. It is poorly soluble in hexane and cold diethyl ether. Trituration or chromatography of crude products with these solvents often leads to a good separation of triphenylphosphine oxide. Its removal is facilitated by conversion to its Mg(II) complex, which is poorly soluble in toluene or dichloromethane and can be filtered off.[7] An alternative filtration method where ZnCl2(TPPO)2 is formed upon addition of ZnCl2 may be used with more polar solvents such as ethanol, ethyl acetate and tetrahydrofuran.[8]
Coordination chemistry
editnickel(II)-from-xtal-3D-balls.png)
Ph3PO forms a variety of complexes. A representative complex is the tetrahedral species NiCl2(OPPh3)2.[9]
Ph3PO is a common impurity in PPh3. The oxidation of PPh3 by oxygen, including air, is catalysed by many metal ions:
- 2 PPh3 + O2 → 2 Ph3PO
References
edit- ^ "Triphenylphosphine oxide". pubchem.ncbi.nlm.nih.gov. Retrieved 12 December 2021.
- ^ D. E. C. Corbridge "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam. ISBN 0-444-89307-5.
- ^ Spek, Anthony L. (1987). "Structure of a Second Monoclinic Polymorph of Triphenylphosphine Oxide". Acta Crystallographica. C43 (6): 1233–1235. Bibcode:1987AcCrC..43.1233S. doi:10.1107/S0108270187092345.
- ^ Al-Farhan, Khalid A. (1992). "Crystal structure of triphenylphosphine oxide". Journal of Crystallographic and Spectroscopic Research. 22 (6): 687–689. doi:10.1007/BF01160986. S2CID 98335827.
- ^ 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.
- ^ van Kalkeren, H. A.; van Delft, F. L.; Rutjes, F. P. J. T. (2013). "Organophosphorus Catalysis to Bypass Phosphine Oxide Waste". ChemSusChem. 6 (9): 1615–24. Bibcode:2013ChSCh...6.1615V. doi:10.1002/cssc.201300368. hdl:2066/117145. PMID 24039197.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Patent WO 1998007724. "Process for the preparation of 7-alkoxyalkyl-1,2,4-triazolo[1,5-a] pyrimidine derivatives"
- ^ Batesky, Donald C.; Goldfogel, Matthew J.; Weix, Daniel J. (2017). "Removal of Triphenylphosphine Oxide by Precipitation with Zinc Chloride in Polar Solvents". The Journal of Organic Chemistry. 82 (19): 9931–9936. doi:10.1021/acs.joc.7b00459. PMC 5634519. PMID 28956444.
- ^ 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.