Hydrothermal reactions between incomplete cuboidal cluster aqua complexes [M(3)Q(4)(H2O)(9)](4+) and M(CO)(6) (M = Mo, W; Q = S, Se) offer easy access to the corresponding cuboidal clusters M(4)Q(4). The complete series of homometal and mixed Mo/W clusters [Mo(x)W(4-x)Q(4)(H2O)(12)](n+) (x = 0-4, n = 4-6) has been prepared. Upon oxidation of the mixed-metal clusters, it is the W atom which is lost, allowing selective preparation of new trinuclear clusters [Mo-2-WSe4(H2O) (9)](4+) and [MoW2Se4(H2O)(9)](4+). The aqua complexes were converted by ligand exchange reactions into dithiophosphato and thiocyanato complexes, and crystal structures of [W4S4((EtO)(2)PS2)(6)], [MoW3S4((EtO)(2)PS2)(6)], [Mo4Se4((EtO)(2)PS2)(6)], [W4Se4((i-PrO)(2)PS2)(6)], and (NH4)(6)[W4Se4(NCS)(12)].-4H(2)O were determined, Cyclic voltammetry was performed on [Mo(x)W(4-x)Q(4)(H2O)(12)](n+), showing reversible redox waves 6+/5+ and 5+/4+. The lower oxidation states are more difficult to access as the number of W atoms increases. The Mo2WSe4(H2O)(9)](4+) and [MoW2Se4(H2O)(9)](4+) species were derivatized into [Mo2WSe4(acac)(3)(py)(3)](+) and [MoW2Se4(acac)(3)(py)(3)](+), which were also studied by CV. When appropriate, the products were also characterized by FAB-MS and NMR (P-31, H-1) data.