Reactions of Monodithiolene Tungsten(VI) Sulfido Complexes with Copper(I) in Relation to the Structure of the Active Site of Carbon Monoxide Dehydrogenase

Reactions directed at the synthesis of structural analogues of the active site of molybdenum-containing carbon monoxide dehydrogenase have been investigated utilizing [WO2S(bdt)]2− (1) and [WOS2(bdt)]2− (2) and sterically hindered [Cu(R)L] or [Cu(SSiR′3)2]− as reactants. All successful reactions of 2 afford the binuclear WVI/CuI products [WO(bdt)(μ2-S)2Cu(L)]2−/− with L = carbene (3), Ar*S (4), Ar* (7), SSiR3 (R = Ph (5), Pri (6)). Similarly, [W(bdt)(OSiPh3)S2]− leads to [W(bdt)(OSiPh3)(μ2-S)2Cu(SAr*)]− (8). These complexes, with apical oxo and basal dithiolato and sulfido coordination (excluding 8), terminal thiolate ligation at CuI (4−6, 8), and W-(μ2-S)-Cu bridging, bear a structural resemblance to the enzyme site. Differences include two bridges instead of one and the absence of basal oxo/hydroxo ligation. Complex 8 differs from the others by utilizing apical and basal sulfido ligands in bridge formation. Related reaction systems based on 1 gave 4 in small yield or product mixtures in which the desired monobridged complex [WO2(bdt)(μ2-S)Cu(R)]2− was not detected. Mass spectrometric analysis of the reaction system with L = carbene suggests that any monobridged species forms may converted to the dibridged form by disproportionation. In these experiments, the use of WVI preserves the structural integrity of MoVI, whose analogues of 1 and 2 have not been isolated. (Ar* = 2,6-bis(2,4,6-triisopropylphenyl)phenyl, bdt = benzene-1,2-dithiolate(2-)).