Phosphonyl Radicals, R2PO and RO 2PO

Phosphonyl radicals can be generated by photolysis or radical abstraction from secondary phosphine oxides, alkyl phosphinates or dialkyl phosphonates. They can be obtained from tertiary butoxy radicals and dialkyl phosphites or tetra alkyl diphosphites (13.175) and (13.176). Phosphonyl radicals react with alkyl halides according to (13.177). 

Phosphoranyl radicals can be prepared either by radical addition to a trivalent phosphorus derivative (13.178), or by a one-electron reduction of a phosphonium salt (13.179). 

Reactions of phosphoranyl radicals are generally more complex than those of the more stable phosphinyl radicals. There are two main types of reaction a scission and P scission. 

Although a scission processes are generally faster than p scission, both process rates are dependent upon the nature of the substituent groups present. In some instances both a and P scission may take place simultaneously. 

When phosphoninm salts are reduced electrolytically to give phosphines and hydrocarbons, the reaction almost certainly involves the initial formation of a phosphoranyl radical. 

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