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RESEARCH PRODUCT

Spin Trapping of Carbon-Centered Ferrocenyl Radicals with Nitrosobenzene

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In contrast to metal centered 17 valence electron radicals, such as [Mn(CO)5]•, ferrocenium ions [Fe(C5H5)2]+ (1+), [Fe(C5Me5)2]+ (2+), [Fe(C5H5)(C5H4Et)]+ (3+), [Fe(C5H5)(C5H4NHC(O)Me)]+ (4+), and [Fe(C5H5)(C5H4NHC(S)Me)]+ (5+) do not add to nitrosobenzene PhNO to give metal-coordinated stable nitroxyl radicals. In the presence of the strong and oxidatively stable phosphazene base tert-butylimino-tris(dimethylamino)phosphorane, the quite acidic ferrocenium ions 1+–5+ are deprotonated to give a pool of transient and persistent radicals with different deprotonation sites [1–Hx]•–[5–Hx]•. One rather persistent iron-centered radical [4–HN]•, deprotonated at the nitrogen atom, has been detected by rapid-freeze EPR spectroscopy at 77 K. This iron-centered radical [4–HN]• is also inert toward PhNO. The transient carbon-centered radicals [1–Hx]•–[5–Hx]• appear to rapidly abstract hydrogen atoms from the adjacent base or the solvent to regenerate the corresponding ferrocenes 1–5. These transient radicals are only...