Triphenylphosphine oxide
Triphenylphosphine oxide (often abbreviated TPPO) is the organophosphorus compound with the formula Template:Chem2, also written as Template:Chem2 or Template:Chem2 (Ph = [[phenyl|Template:Chem2]]). 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
Template:Chem2 is structurally related to Template:Chem2.[1] As established by X-ray crystallography, the geometry around P is tetrahedral, and the P-O distance is 1.48 Å.[2] Other modifications of Template:Chem2 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.[3]
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.[4]
As a byproduct of organic synthesis
Template:Chem2 is a byproduct of many useful reactions in organic synthesis including the Wittig, Staudinger, and Mitsunobu reactions. It is also formed when Template:Chem2 is employed to convert alcohols into alkyl chlorides:
Triphenylphosphine can be regenerated from its oxide by treatment with a variety of deoxygenation agents, such as phosgene or trichlorosilane/triethylamine:[5]
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.[6] An alternative filtration method where Template:Chem2 is formed upon addition of Template:Chem2 may be used with more polar solvents such as ethanol, ethyl acetate and tetrahydrofuran.[7]
Coordination chemistry
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Template:Chem2 forms a variety of complexes. A representative complex is the tetrahedral species Template:Chem2.[8]
Template:Chem2 is a common impurity in [[Triphenylphosphine|Template:Chem2]]. The oxidation of Template:Chem2 by oxygen, including air, is catalysed by many metal ions:
References
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- ↑ D. E. C. Corbridge "Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology" 5th Edition Elsevier: Amsterdam. Template:ISBN.
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- ↑ Patent WO 1998007724. "Process for the preparation of 7-alkoxyalkyl-1,2,4-triazolo[1,5-a] pyrimidine derivatives"
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