Synthesis, structures, and properties of molybdenum and tungsten chalcogenide cubane complexes (NH4)6[M4Q4(CN)12]·6H2O (M=Mo or W; Q=S or Se)

Four new chalcogenide molybdenum and tungsten cubane clusters (NH4)6[M4Q4(CN)12]·6H2O (M=Mo or W; Q=S or Se) were prepared by high-temperature reactions of the triangular M3O7Br4 complexes with KCN at 430 °C followed by crystallization from aqueous solutions of ammonium acetate. The molecular and crystal structures of (NH4)6[Mo4S4(CN)12]·6H2O, (NH4)6[W4S4(CN)12]·6H2O, and (NH4)6[W4Se4(CN)12]·6H2O were established by X-ray diffraction analysis. The mixed-valence cubane clusters are diamagnetic and isostructural and have the symmetryTd. The clusters were characterized by IR and electronic spectroscopy. The data of cyclic voltammetry demonstrated that the [M4Q4(CN)12]n− clusters exist in three oxidation states from the most oxidized (n=6; 10 cluster electrons) to the most reduced electron-precise 12-electron species (n=8).