The [MoCu] carbon monoxide dehydrogenase (CODH) is a Cu-containing molybdo-flavoprotein, the active site of which contains a pterin-dithiolene cofactor bound to a sulfido-bridged dinuclear Mo-Cu complex. In this paper, the synthesis and characterization of dinuclear Mo-Cu complexes relevant to the active site of [MoCu]-CODH are described. Reaction Of [MoO2S2](2-) with CuCN affords the dinuclear complex [O2MoS2Cu(CN)](2-) (1), in which the CN- ligand can be replaced with various aryl thiolates to give rise to a series of dinuclear complexes [O2MoS2Cu(SAr)](2-) (Ar = Ph (2), o-Tol (3), and p-Tol (4)). An alternative synthesis of complex 2 is the reaction Of [MoO2S2](2-) with [Cu(SPh)(3)](2-). Similarly, [O2MoS2Cu(PPh3)](-) (5), [O2MoS2Cu(dppe)](-) (dppe = 1,2-bis-(diphenylphosphino)ethane) (6), and [O2MoS2Cu(triphos)](-) (triphos = 1,1,1-tris[(diphenylphosphino)methyl]ethane) (7) were prepared from the reactions of [MoO2S2](2-) with the Cu(I) phosphine complexes. Treatment of 1, 2, 4, or 5 with dithiols (1,2-(SH)(2)C6H4, 1,2-(SH)(2)C6H2-3,6-Cl-2, and 1,2-(SH)(2)C2H4), in acetonitrile, leads to the replacement of a molybdenum-bound oxo ligand to yield [(dithiolate)Mo(O)S2CuL](2-) (L = CN, SAr; dithiolate = 1,2-S2C6H4, 1,2-S2C6H2-3,6-Cl-2, or 1,2-S2C2H4) (8-13) or [(1,2-S2C6H4)Mo(O)S2Cu(PPh3)](-) (14) complexes.