Unstable intermediates. Part 165. Radicals in irradiated organolead compounds: an electron spin resonance study

Abstract

Exposure of PbPh₃Cl and PbBrPh₃ to ⁶⁰Co γ-rays at 77 K gives centres having ²⁰⁷Pb and ³⁵Cl or ⁸¹Br hyperfine coupling constants consistent with expectation for the parent radical anions. The electron-loss centres are thought to be the corresponding cations, with the hole largely confined to the halogen atoms. Irradiated PbMe₃Cl gives a similar anionic centre in methanolic solution, but the pure material gives largely Me˙ and PbMe₂(ĊH₂)Cl radicals. Irradiated PbMe₄ and PbEt₄ pure or in toluene at 77 K. give centres thought to be PbR₃˙ radicals having g_⊥≈ 2.1 and g_∥≈ 1.9, and abnormally large anisotropic ²⁰⁷Pb hyperfine coupling constants. In addition, PbMe₄ gives a centre thought to be [PbMe₄]^–˙ and both give R˙ and PbMe₃(ĊH₂) or PbEt₃(ĊHMe). Irradiated Pb₂Ph₆ gives only one clearly defined paramagnetic centre, tentatively identified as the parent anion.