Synthesis, structure, and properties of molybdenum and tungsten cyano complexes with cuboidal M-4(mu(3)-E)(4) (M = Mo, W; E = S, Se, Te) cores

Four new tungsten and molybdenum cyano complexes of formula KCs5[W4S4(CN)(1 2)]. CH3OH . 2H(2)O (1), K-6[W-4- Se-4(CN)(12)]. 6H(2)O (2), K-6[W4Te4(CN)( 12)]. 5H(2)O (3), and K-7[Mo4Te4(CN)(12)]. 12H(2)O (5) have been prepared b y high-temperature 430-450 degrees C reaction of the polymeric chain compou nds {W3S7Br4}(x), {W3Se7Br4}(x), {Mo3Te7I4}(x) and solid-state WTe2 with KC N, and crystallization from aqueous solutions. In addition Cs-6[Mo4Te4(CN)( 12)]. 2H(2)O (4) has been prepared by oxidation of 5 with bromine water. Th e molecular structures have been investigated by X-ray crystallography. Mix ed-valence (3.5) compounds 1-4 are diamagnetic. Mixed-valence (3.25) compou nd 5 is paramagnetic (mu = 2.03 mu(B) at 77 K). In addition to the structur al data for these complexes IR and UV-vis spectroscopy have been used to ch aracterize the complexes. Cyclic-voltammetry data have shown that M4E4n+ (M = Mo, W; E = S, Se, Te) cubes are capable of existing in three oxidation s tates ranging from the most oxidized (n = 6; 10 electrons) to the most redu ced electron-precise (n = 4; 12 electrons). The Se-77, Te-125, and W-183 NM R spectra of the cubes (1-3) demonstrate unambiguously the unaltered enviro nments of the W and E atoms in aqueous solution.