Aqueous solution chemistry of [Mo3CuSe4]n+ (n=4, 5) and [W3CuQ4]5+ (Q = S, Se) clusters

The triangular cluster [Mo3Se4(H2O)(9)](4+) reacts with Cu turnings to give it new heterometallic cuboidal cluster [Mo3CuSe4(H2O)(10)](4+) (purple; UV/Vis lambda(epsilon): 352(3907), 509(2613)). The reaction of [Mo3Se4(H2O)(9)](4+) with CuCl afforded the 5+ cube [Mo3CUSe4(H2O)(10)](5+) (red; UV/Vis lambda(epsilon): 356(5406), 500(3477)). In contrast, [W3Se4(H2O)(9)](4+) both with Cu and CuCl gives the 5+ cube, [W3CuSe4(H2O)(10)](5+) (yellow-green UV/Vis lambda(epsilon): 312(5327), 419(3256) and 628(680)). Cyclic voltammetry of [M(3)CuQ(4)(H2O)(10)](5+) in 2 M HCl (M = Mo, W; Q = S, Se) shows a reversible one-electron reduction wave for the Mo clusters, but no reduction occurs for the W clusters prior to H+ reduction. In HCl Solutions, Cl is coordinated to the Cu site of the clusters, alongside some less extensive coordination to Mo and W, and for [W-3(CuCl)S-4(H2O)(6)Cl-3](+) isolated as the supramolecular adduct with cucurbit[6]uril, [W-3(CuCl)S-4(H2O)(6)Cl-3](2)Cl-2.C36H36N24O12.12H(2)O, the crystal Structure was determined (Cu-W 2.856(4) Angstrom, W-W 2.7432(15) Angstrom, Cu-Cl 2.167(13) Angstrom).