Synthesis, structures, and properties of molybdenum and tungsten chalcogenide cubane complexes (NH4)(6)[M(4)Q(4)(CN)(12)]center dot 6H(2)O (M = Mo orW ; Q = S or Se)

Four new chalcogenide molybdenum and tungsten cubane clusters (NH4)(6)[M(4) Q(4)(CN)(12)] . 6H(2)O (M = Mo or W; Q = S or Se) were prepared by high-tem perature reactions of the triangular M(3)Q(7)Br(4) complexes with KCN at 43 0 degrees C followed by crystallization from aqueous solutions of ammonium acetate. The molecular and crystal structures of (NH4)(6)[Mo4S4(CN)(12)]. 6 H(2)O, (NH4)(6)[W4S4(CN)(12)] . 6H(2)O, and (NH4)(6)[W4Se4(CN)(12)] . 6H(2) O were established by X-ray diffraction analysis. The mixed-valence cubane clusters are diamagnetic and isostructural and have the symmetry T-d. The c lusters were characterized by IR and electronic spectroscopy. The data of c yclic voltammetry demonstrated that the [M(4)Q(4)(CN)(12)](n-) clusters exi st in three oxidation states from the most oxidized (n = 6; 10 cluster elec trons) to the most reduced electron-precise (.)12-electron species (n = 8).