An electron spin resonance study of radical addition to bis(trimethylsilyl)amino(trimethylsilylimino)phosphine, (Me3Si)2NPNSiMe3

Abstract

Alkoxyl, alkyl, and acyl radicals add rapidly to phosphorus in the phospha(III)azene (Me₃Si)₂NṖNSiMe₃ to give phosphorimidoyl radicals X[(Me₃Si)₂N]PNSiMe₃(4; X = RO, R, or RCO) which are nitrogen analogues of the phosphonyl radicals Y₂ṖO. The solution e.s.r. spectra of the phosphorimidolyl radicals are characterised by large values of a(³¹P)[519 G for (4; X = Bu^tO) at 173 K] which are indicative of a pyramidal geometry at phosphorus. The phosphorimidoyl radicals are relatively persistent [t_1/2ca. 25 s for the decay of (4; X = Bu^t) at 292 K] and their addition to ethylene could not be detected by e.s.r. spectroscopy. This lack of reactivity is ascribed mainly to steric shielding of the radical centre by the bulkyl trimethylsilyl groups.