Six [Fe8(μ4-O)4(μ-4-R-pyrazolato) 12X4] complexes containing an identical Fe 8(μ4-O)4 core have been structurally characterized and studied by Mossbauer spectroscopy. In each case, an inner μ4-O bridged Fe'" cubane core is surrounded by four trigonal bipyramidal iron centers, the two distinct sites occurring in a 1:1 ratio. The Mössbauer spectrum of each of the clusters consists of two quadrupole doublets, which, with one exception (X = NCS, R = H), overlap to give three absorption lines. The systematic variation of X and R causes significant changes in the Mössbauer spectra. A comparison with values for the same clusters computed using density functional theory allows us to establish an unequivocal assignment of these peaks in terms of a nested model for the overlapping doublets. The changes in Mossbauer parameters (both experimental and computed) for the 1-electron reduced species [Fe8(μ4- O) 4(μ-4-Cl-pyrazolato)12Cl4]- are consistent with a redox event that is localized within the cubane core. © 2010 American Chemical Society.
