Heterocubane cluster compounds (NEt4){Y=M[(mu(3)-S)Re(CO)(3)](3)(mu(3)-E)}(M = W or Mo, Y = O or S, E = S or Se): Structures, spectroscopy, and electrochemistry

Thiometallates [MS4](2-) (M = Mo, W) or [WOS3](2-) react with Re(CO)(5)(O3S CF3) and Li2E (E = S or Se) to yield the following compounds which were str ucturally characterized: (NEt4){S=W[(mu (3)-S)Re(CO)(3)](3)(mu (3)-S)}(NEt4 ) (1), (NEt4){O/S=W[(mu (3)-S)Re(CO)(3)](mu (3)-S)}(NEt4) (1/2), (mixed cry stals), (NEt4){S=W[(mu (3)-S)Re(CO)(3)](3)(mu (3)-Se)}(NEt4) (3) and (NEt4) {S=Mo[(mu (3)-S)Re(CO)(3)](3)(mu (3)-S)}(NEt4) (4). The hetero-cubane anion s 1-4 contain electron-rich centers such as rhenium(I) or sulfide whereas m olybdenum(VI) or tungsten(VI) act as acceptor sites. Accordingly, the absor ption spectra show long-wavelength metal-to-ligand charge transfer transiti ons, and cyclic voltammetry reveals a quasi-reversible reduction of the clu sters. Although both six-coordinate rhenium(I) and four-coordinate metal(VI ) centers are present in the clusters there is no evidence for significant metal-to-metal charge transfer interaction.