Electron spin resonance studies of radicals derived from trialkyl phosphorimidates, (RO)3PNR. Phosphazene formation by β-scission of an aminophosphoranyl radical
Abstract
Using e.s.r. spectroscopy it has been shown that the phosphoranyl radical (EtO)3ṖN(CH2Ph)SiMe3 undergoes β scission to form a benzyl radical and the phosphorimidate (EtO)3PNSiMe3(identified by 31P n.m.r. spectroscopy). Methyl and diethoxyphosphonyl radicals do not add sufficiently rapidly to nitrogen in (EtO)3PNMe to produce a detectable concentration of phosphoranyl radicals, but the phosphonyl radical adduct has been generated indirectly by addition of ethoxyl radicals to the trivalent phosphorus atom in (EtO)2P(O)N(Me)P(OEt)2, itself prepared by the reaction of (EtO)2PCl with (EtO)3PNMe. Hydrogen abstraction from trialkyl phosphorimidates (RO)3PNC(H)R2 a potential route to iminophosphoranyl radicals (RO)3ṖNCR2, gives rise to π-radicals (RO)3PNĊR2 which may be regarded as imine radical anions carrying a phosphonium substituent on nitrogen. These species do not break down readily to give iminyl radicals and phosphite, and addition of R2CN· to (RO)3P is not detectable by e.s.r. spectroscopy.