Synthesis of triphenylphosphine oxide by oxidation of triphenylphosphine by oxygen under the catalytic effect of iron compounds

Triphenylphosphine oxide, OP(C6H5)3, can be conveniently prepared by oxidation of triphenylphosphine, P(C6H5)3, by oxygen under the catalytic effect of iron compounds such as FeX3 FeX3[OP(C6H5)3]2, (X = Cl, Br, NCS), or FeCl3[P(C6H5)32]. The highest catalytic effect was observed in the case of the complexes containing the bromo or thiocyanato ligands. The oxidation in acetonitrile solution is quantitative and selective at 30 - 70 °C and atmospheric pressure of oxygen gas.