Spin density cyclopentadienyl complexes

The authors found that the in situ electrochemical potentiokinetic reactivation (EPR) data obtained for the monocation I" " showed that the two Mn centers had identical spin densities, and hence the cation showed delocalized mixed valence the near-infrared spectrum supported this postulate. If such a delocalized system existed on the infrared timescale, then two bands would be expected in the carbonyl region of the infrared spectrum of 1+ at frequencies intermediate between those of the Mn(I)/Mn(I) neutral complex, (1861 and 1934 cm ), and those of the fully oxidized Mn(II)/Mn(II) species, which were predicted to be ca. 1966 and 2048 cm on the basis of the bands observed for CpMn(II)(CO)2PPh3 +, (Cp = cyclopentadienyl). In contrast, four intense CO absorptions were observed near 1888, 1931, 1952, and 2003 cm , which were typical of the trapped valent Mn(II)/Mn(I) species. The variation in the response obtained on the EPR timescale, ca. 10 s, to that observed on the infrared timescale, ca. 10 s, was taken by the authors as implying a time-dependent localization process. 

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