Redox Reactions of a Stable Dialkylphosphinyl Radical

A stable dialkylphosphinyl radical, 2,2,5,5-tatrakis­(trimethylsilyl)-1-phosphacyclopentan-1-yl (R^H₂P^•), showed both irreversible one-electron oxidation and reduction peaks at −0.24 and −2.29 V vs ferrocene/ferrocenium couple. One-electron reduction of R^H₂P^• 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)]⁺[R^H₂P]⁻ and [K­(crypt-222)]⁺[R^H₂P]⁻. Whereas [K­(18-c-6)]⁺[R^H₂P]⁻ exists as a contact ion pair, [K­(crypt-222)]⁺[R^H₂P]⁻ exists as a solvent-separated ion pair in the solid state. Reaction of R^H₂P^• with AgOTf afforded an unexpected product, a silver­(I) phosphaalkene complex