Molybdenum–copper–sulfur Mo3CuS4 cubes

Reaction of the incomplete cubane-type cluster [Mo3S4(H2O)9]4+ (1) with CuCl in 2 M HCl gives a novel cubane-type cluster [Mo3CuS4Cl(H2O)9]4+ (2). The nitrilotriacetato complex [Mo3CuS4Cl(Hnta)3]2− (3), the derivative of 2, has been prepared. The crystallographic results obtained were as follows: K2[Mo3CuS4Cl(Hnta)3]·9H2O (3a), triclinic, P1, a=10.634(1), b=11.032(2), c=10.299(4) Å, α=112.34(2), β=98.76(2), γ=81.91(1)°, V=1100.3(4) Å3, Z=1, R=5.7%; (NH4)2[Mo3CuS4Cl(Hnta)3]·9H2O (3b), triclinic, P1, a=10.714(1), b=11.121(1), c=10.379(3) Å, α=112.07(1), β=99.375(8), γ=81.168(7)°, V=1124.9(4) Å3, Z=1, R=8.3%; (NH4)2[Mo3CuS4Cl(Hnta)3]·9H2O (3c) trigonal, R3m, a=16.332(2), c=14.301(2) Å, V=3303.5(4) Å3, Z=3, R=4.2%. Binding energies of Cu 2p3/2, Cu 2p1/2, Mo 3d5/2, and Mo 3d3/2 from X-ray photoelectron spectroscopy measurements are 933.35, 953.26, 230.07 and 233.24 eV for 3a, 933.47, 953.25, 230.18 and 233.31 eV for 3b, respectively (C1s=285.0 eV). The binding-energy values of Cu 2p3/2 for 3a and 3b and the absence of satellites indicate the Cu(I) oxidation state in the respective clusters. The comparison of [Mo3CuS4Cl(H2O)9]4+ (2) in hydrochloric acid with [Mo3CuS4(H2O)10]5+ (2′) in Hpts reveals that the coordination of chloride ion to copper atom increases very much the stability of 2 in hydrochloric acid solution. Air oxidation of [Mo3CuS4Cl(H2O)9]3+ (4) and [Mo3CuS4(H2O)10]4+ (4′) and the reaction and reaction products of [Mo3FeS4(H2O)10]4+ (5) with Cu(II) ion will be discussed.