Redox Reactions of a Stable Dialkylphosphinyl Radical

A stable dialkylphosphinyl radical, 2,2,5,5-tatrakis-(trimethylsilyl)-1-phosphacyclopentan-1-yl ((R2P)-P-H center dot), showed both irreversible one-electron oxidation and reduction peaks at -0.24 and -2.29 V vs ferrocene/ferrocenium couple. One-electron reduction of (R2P)-P-H center dot with KC8 in the presence of 18-crown-6 (18-c-6) or [2.2.2]cryptand (crypt-222) gave the corresponding phosphides [K(18-c-6)]+[(R2P)-P-H](-) and [K(crypt-222)]+[(R2P)-P-H](-). Whereas [K(18-c-6)]+[(R2P)-P-H](-) exists as a contact ion pair, [K(crypt-222)]+[(R2P)-P-H](-) exists as a solvent-separated ion pair in the solid state. Reaction of (R2P)-P-H center dot with AgOTf afforded an unexpected product, a silver(I) phosphaalkene complex.