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.