Bis(benzene)chromium [(η6-C6H6)2Cr] (BBC) is shown to readily trap radical species R (R = H, D, isobutyronitrile (IBN)) to form complex paramagnetic adducts whose structure has been identified in frozen solution by ENDOR (electron nuclear double resonance spectroscopy). It is shown that radical attack yields the 17 valence electron species (η6-C6H6)(η5-C6H6R)Cr where R assumes the endo position of the η5-ring with respect to the metal in a dynamic interannular migration mediated by the central metal atom. It is further shown that PhSiH3 (Ph = phenyl) is an efficient source of hydrogen atoms in the presence of BBC as well as other conventional nitroxide spin traps.