Electronic properties of certain component members of electron-transfer series 1 and 2 formed by the double-cubane clusters [Mo2Fe6S8(SR)9]z (1, z = 2to 5-) and [Mo2Fe6S8(^2-OMe)3(S-r-Bu)6]z (2, z = 1to 5-) have been investigated. The series are generated by one-electron reactions of MoFe3S4 subclusters, which are usually reversible by cyclic voltammetry; 3-, 4-, and 5members are the more stable and have been produced in solution by electrochemical and chemical reactions. The 5member of series 1 with R = Ph has been isolated. ( Et4N)5 [Mo2Fe6S8(SPh)9] crystallizes in monoclinic space group P2\/c with a = 18.937 (2) Á, 6 = 26.637 (3) Á, c = 22.534 (2) Á, ß = 94.30 (2)°, and Z = 4; the structure was refined to R = 6.6% by using 6517 unique data (F02 > 2.5a(F02)). The cluster retains the double-cubane structure of [Mo2Fe6S8(SR)9]3s pecies but with an increased ••• separation and subcluster dimensional changes (e.g., a mean volume increase of 2.6%) consistent with reduction. Isomer shifts derived from fits of low-temperature Móssbauer spectra have been used to follow changes in subcluster charge distribution in series 1. The mean oxidation states Fe2,67+ and Fe2,33+ are considered the most probable for the 3and 5clusters, respectively, of these series. The 4member of series 1 is concluded to possess (on the Móssbauer time scale at T < 80 K) inequivalent subclusters containing Fe2,67+ and Fe2,33+. Absorption spectra and magnetic properties are consistent with this assignment. Collective spectroscopic and redox potential properties serve to demonstrate that electronic structural changes attendant to 3-/4-and 4-/5electron-transfer reactions of double cubanes are largely confined to subcluster Fe3 portions and associated sulfur atoms. Assigned (mean) oxidation states of Fe and Mo atoms are intended
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