Of phosphorus trihalides and halophosphines

Phosphorus trichloride adds to olefins both in a radical reaction32 and in presence of A1C13.33 The former type of reaction gives alkyldichlorophos-phines, but, after hydrolytic working up, the latter affords cyclic phosphinic chlorides or phosphinic acids. Neither reaction has been studied in detail. 

Phosphonic dichlorides are obtained when oxygen is led into a mixture of PC13 and an olefin.34 This reaction sometimes occurs at temperatures much below 0° the yields vary greatly but are particularly poor for the lower olefins. Haloolefins and acrylic acid derivatives often give good yields, but usually of mixed isomers. 

Phosphinic chlorides are obtained analogously from alkyl- or aryl-dichloro-phosphines35,36 (cf. page 735). 

3-Dienes add alkyl- or aryl-dihalophosphines37 in a kind of Diels-Alder reaction. According to the structures of the diene and phosphorus components either the expected 1-alkyl- or l-aryl-3-phospholene 1,1-dihalide (1) or the isomeric 2-phospholene derivative (2) is formed.38,39 

Since the double-bond isomerization was at first unrecognized and later recognized only in the hydrolysis products, the position of the double bond in most of the compounds described in the literature must be regarded as uncertain. The only proved facts seem to be that with isoprene dichloro(phenyl)-phosphine gives the 2-phospholene derivative, that dichloro(methyl)phosphine and dibromo(phenyl)phosphine give the 3-phospholene, whereas also with 2,3-dimethylbutadiene dichloro(phenyl)phosphine gives the non-isomerized product of type (1).38,39 

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