Triphenylphosphine oxide (often abbreviated TPPO) is theorganophosphorus compound with the formulaO=P(C6H5)3, also written asPh3PO orPPh3O (Ph =C6H5). It is one of the more commonphosphine oxides. This colourless crystalline compound is a common but potentially useful waste product in reactions involvingtriphenylphosphine. It is a popular reagent to induce thecrystallizing of chemical compounds.
Ph3PO is structurally related toPOCl3.[2] As established byX-ray crystallography, the geometry around P is tetrahedral, and the P-O distance is 1.48Å.[3] Other modifications ofPh3PO have been found: For example, a monoclinic form crystallizes in the space groupP21/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 groupPbca with Z = 4 and 29.089(3) Å, b = 9.1347(9), c = 11.261(1) Å.[4]
Theoxygen 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 haveacidic hydrogen atoms, e.g.phenols.[5]
Triphenylphosphine oxide can be difficult to remove from reaction mixtures by means ofchromatography. It is poorly soluble inhexane and colddiethyl 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 itsMg(II)complex, which is poorly soluble intoluene ordichloromethane and can be filtered off.[7] An alternative filtration method whereZnCl2(TPPO)2 is formed upon addition ofZnCl2 may be used with morepolar solvents such asethanol,ethyl acetate andtetrahydrofuran.[8]
^Al-Farhan, Khalid A. (1992). "Crystal structure of triphenylphosphine oxide".Journal of Crystallographic and Spectroscopic Research.22 (6):687–689.doi:10.1007/BF01160986.S2CID98335827.
^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.
nickel(II)-from-xtal-3D-balls.png)
