Issue 6, 1979

An electron spin resonance study of radical addition to vinylphosphines

Abstract

E.s.r. spectroscopy has been used to show that alkoxyl and methyl radicals add to phosphorus in the vinylic phosphines R2C[double bond, length half m-dash]C(H)PX2(X = MeO, EtO, or Me2N) to form ‘phosphoranyl’ radicals in which the unpaired electron is centred mainly on the remote carbon. These adducts are π-radicals and can be regarded as alkene radical anions which carry a phosphonium substituent, although there is significant spin density on phosphorus. The adducts R2Ċ–C(H)[double bond, length half m-dash]P(OR′)2OBut(R = H or Me) undergo fragmentation to give t-butyl radicals and the phosphonate ester R2C[double bond, length half m-dash]C(H)P(O)(OR′)2.

t-Butyl radicals add to the unsubstituted carbon of the vinyl group in H2C[double bond, length half m-dash]C(H)PX2(X = RO, Me2N, or Et) to give α-phosphinoalkyl radicals ButCH2Ċ(H)PX2, the e.s.r. spectra of which exhibit relatively large splitting from 31P. There appears to be appreciable delocalisation of the unpaired electron onto phosphorus, a result which was not anticipated on the basis of previous reports of e.s.r. spectra ascribed to α-phosphinoalkyl radicals.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 2, 1979, 781-787

An electron spin resonance study of radical addition to vinylphosphines

J. A. Baban, C. J. Cooksey and B. P. Roberts, J. Chem. Soc., Perkin Trans. 2, 1979, 781 DOI: 10.1039/P29790000781

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