triphenylphosphine oxide
{{chembox
| Watchedfields = changed
| verifiedrevid = 470616901
| Name = Triphenylphosphine oxide
| ImageFile = Triphenylphosphine-oxide-2D-skeletal.png
| ImageName = Triphenylphosphine oxide
| ImageFile1 = Triphenylphosphine-oxide-from-xtal-3D-vdW-A.png
| ImageName1 = Triphenylphosphine oxide
| ImageFile2 = Sample of Triphenylphosphine oxide.jpg
| ImageSize2 = 180px
| PIN = Triphenyl-λ5-phosphanone
| OtherNames = Triphenylphosphine oxide
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 791-28-6
| Beilstein = 745854
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 36601
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 482091
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 12549
| EC_number = 212-338-8
| Gmelin = 6758
| PubChem = 13097
| RTECS = SZ1676000
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = Z69161FKI3
| InChI = 1/C18H15OP/c19-20(16-10-4-1-5-11-16,17-12-6-2-7-13-17)18-14-8-3-9-15-18/h1-15H
| InChIKey = FIQMHBFVRAXMOP-UHFFFAOYAB
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C18H15OP/c19-20(16-10-4-1-5-11-16,17-12-6-2-7-13-17)18-14-8-3-9-15-18/h1-15H
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = FIQMHBFVRAXMOP-UHFFFAOYSA-N
| SMILES = O=P(c1ccccc1)(c2ccccc2)c3ccccc3
}}
|Section2={{Chembox Properties
| Formula = {{chem2|OP(C6H5)3}}
| C=18|H=15|O=1|P=1
| Appearance = white crystals
| Density = 1.212 g/cm3
| Solubility = low
| Solvent = other solvents
| SolubleOther = polar organic solvents
| MeltingPtC = 154 to 158
| MeltingPt_notes =
| BoilingPtC = 360
| BoilingPt_notes =
}}
|Section3={{Chembox Structure
| MolShape = tetrahedral
| Dipole =
}}
|Section7={{Chembox Hazards
| ExternalSDS =
| MainHazards = Harmful if swallowed. Harmful to aquatic life with long lasting effects.
| GHSPictograms = {{GHS07}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|302|412}}
| PPhrases = {{P-phrases|261|264|270|271|273|280|301+312|302+352|304+340|305+351+338|312|330|332+313|337+313|362|403+233|405}}
}}
|Section8={{Chembox Related
| OtherCompounds = {{ubl|Triphenylphosphine sulfide|Triphenylphosphine|Phosphoryl chloride|Phosphorus pentachloride}}
}}
}}
Triphenylphosphine oxide (often abbreviated TPPO) is the organophosphorus compound with the formula {{chem2|O\dP(C6H5)3|auto=1}}, also written as {{chem2|Ph3PO}} or {{chem2|PPh3O}} (Ph = phenyl). 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.
Structure and properties
{{chem2|Ph3PO}} is structurally related to {{chem2|POCl3}}.D. E. C. Corbridge "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam. {{ISBN|0-444-89307-5}}.
As established by X-ray crystallography, the geometry around P is tetrahedral, and the P-O distance is 1.48 Å.{{cite journal|doi=10.1107/S0108270187092345|title=Structure of a Second Monoclinic Polymorph of Triphenylphosphine Oxide|year=1987|last1=Spek|first1=Anthony L.| journal=Acta Crystallographica|volume=C43|issue=6|pages=1233–1235|bibcode=1987AcCrC..43.1233S}} Other modifications of {{chem2|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.{{cite journal|doi=10.1007/BF01160986|title=Crystal structure of triphenylphosphine oxide|year=1992|last1=Al-Farhan|first1=Khalid A.|journal=Journal of Crystallographic and Spectroscopic Research|volume=22|issue=6|pages=687–689|s2cid=98335827}}
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.{{cite journal | author = M. C. Etter and P. W. Baures | title = Triphenylphosphine oxide as a crystallization aid | year = 1988 | journal = J. Am. Chem. Soc. | volume = 110 | issue = 2 | pages = 639–640 | doi=10.1021/ja00210a076}}
As a byproduct of organic synthesis
{{chem2|Ph3PO}} is a byproduct of many useful reactions in organic synthesis including the Wittig, Staudinger, and Mitsunobu reactions. It is also formed when {{chem2|PPh3Cl2}} is employed to convert alcohols into alkyl chlorides:
:{{chem2|Ph3PCl2 + ROH → Ph3PO + HCl + RCl}}
Triphenylphosphine can be regenerated from its oxide by treatment with a variety of deoxygenation agents, such as phosgene or trichlorosilane/triethylamine:{{cite journal|author=van Kalkeren, H. A.; van Delft, F. L.; Rutjes, F. P. J. T.|title=Organophosphorus Catalysis to Bypass Phosphine Oxide Waste|journal=ChemSusChem|year=2013|volume=6|issue=9|pages=1615–24|doi=10.1002/cssc.201300368|pmid=24039197|bibcode=2013ChSCh...6.1615V |hdl=2066/117145|hdl-access=free}}
:{{chem2|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.Patent WO 1998007724. "Process for the preparation of 7-alkoxyalkyl-1,2,4-triazolo[1,5-a] pyrimidine derivatives" An alternative filtration method where {{chem2|ZnCl2(TPPO)2}} is formed upon addition of {{chem2|ZnCl2}} may be used with more polar solvents such as ethanol, ethyl acetate and tetrahydrofuran.{{Cite journal|last1=Batesky|first1=Donald C.|last2=Goldfogel|first2=Matthew J.|last3=Weix|first3=Daniel J.|title=Removal of Triphenylphosphine Oxide by Precipitation with Zinc Chloride in Polar Solvents|journal=The Journal of Organic Chemistry|language=en|year = 2017| volume=82|issue=19|pages=9931–9936|doi=10.1021/acs.joc.7b00459|pmid=28956444|pmc=5634519|doi-access=free}}
Coordination chemistry
File:Dichlorobis(triphenylphosphine-oxide)nickel(II)-from-xtal-3D-balls.png
{{chem2|Ph3PO}} forms a variety of complexes. A representative complex is the tetrahedral species {{chem2|NiCl2(OPPh3)2}}.{{cite journal | author = D. M. L. Goodgame and M. Goodgame | title = Near-Infrared Spectra of Some Pseudotetrahedral Complexes of Cobalt (II) and Nickel(II) | year = 1965 | journal = Inorg. Chem. | volume = 4 | issue = 2 | pages = 139–143 | doi=10.1021/ic50024a002}}
{{chem2|Ph3PO}} is a common impurity in Triphenylphosphine. The oxidation of {{chem2|PPh3}} by oxygen, including air, is catalysed by many metal ions:
:{{chem2|2 PPh3 + O2 → 2 Ph3PO}}
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