BIS(BENZENE)CHROMIUM - A SANDWICH COMPLEX SPIN TRAP AS REVEALED BY ENDOR SPECTROSCOPY

Bis(benzene)chromium [(eta(6)-C6H6)(2)Cr] (BBC) is shown to readily tr ap radical species R (R = H, D, isobutyronitrile (IBN)) to form comple x paramagnetic adducts whose structure has been identified in frozen s olution by ENDOR (electron nuclear double resonance spectroscopy). It is shown that radical attack yields the 17 valence electron species (e ta(6)-C6H6)(eta(5)-C6H6R)CT where R assumes the endo position of the e ta(5)-ring with respect to the metal in a dynamic interannular migrati on mediated by the central metal atom. It is further shown that PhSiH3 (Ph = phenyl) is an efficient source of hydrogen atoms in the presenc e of BBC as well as other conventional nitroxide spin traps.