Spin Trapping of Carbon-Centered Ferrocenyl Radicals with

This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.

Article pubs.acs.org/Organometallics

Spin Trapping of Carbon-Centered Ferrocenyl Radicals with Nitrosobenzene Andreas Neidlinger,† Torben Kienz,† and Katja Heinze* Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg-University, Duesbergweg 10-14, D-55128 Mainz, Germany S Supporting Information *

ABSTRACT: 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 present in trace amounts (