The synthesis and structural characterization of the neutral mixed-valence methoxo-polyoxo-vanadium cluster [V6O8(OCH3)(11)] (1) and its single oxidation product in the hexachloroantimonate salt [V6O8(OCH3)(11)][SbCl6] (2) are presented here. The cluster comprises a hexauclear polyoxovanadate core of the Lindqvist structure, of which all but one of the mu-bridging oxo ligands are substituted by methoxo. As revealed by cyclic voltammetry, the cluster is highly redox active, displaying several further thermodynamically stable V-IV/V-V mixed-valence redox derivatives. Furthermore, valence sum calculations performed on the X-ray structural data as well as results from IR and UV-vis spectrometry characterize them as class II mixed-valence compounds. In the present article, we equally present results from cyclic voltammetry, UV-vis spectrometry, and magnetic measurements obtained for members of the previously reported [V6O7(OCH3)(12)] cluster series, which, as opposed to 1 and its derivatives, contain exclusively methoxo ligands asy-bridging moieties. Magnetic measurements performed on the highly reduced cluster species [(V5V1O7)-V-IV-O-V(OCH3)(12)](-) and [(V6O7)-O-IV(OCH3)(12)](2-) reveal net antiferromagnetic exchange interactions between the cl-electrons, which at lower temperatures are in part suppressed for reasons attributed to geometric spin frustration. Among the present results, the comparison of the cyclic voltammograms of 1 and [V6O7(OCH3)(12)] has proven to be of considerable interest, showing an unexpectedly pronounced discrepancy in all but one of their corresponding redox potentials. In particular, a detailed analysis of the electrochemical conversions indicates that the observed shift is almost entirely the result of a different degree of d-electron spin-spin interactions in corresponding mixed valence species of the cluster series.
