Oxidation of tris(2,4,6-triisopropylphenyl)phosphine and arsine

A reaction of the radical cation of tris(2,4,6-triisopropylphenyl)phosphine with oxygen gave a phosphonium salt resulting from the introduction of the oxygen atom to the phosphorus and the formation of a five membered ring by participation of the ortho isopropyl group. On the other hand, oxidation of the phosphine with mCPBA afforded the corresponding phosphine oxide. X-ray crystallography showed that the CPC bond angles and the PC bond lengths of the phosphine oxide are similar to those of the corresponding phosphine. The corresponding arsine underwent analogous reactions to afford the arsonium salt and the arsine oxide.