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 [MoO S ] with CuCN affords the dinuclear complex [O MoS Cu(CN)] (1), in which the CN ligand can be replaced with various aryl thiolates to give rise to a series of dinuclear complexes [O MoS Cu(SAr)] (Ar = Ph (2), o-Tol (3), and p-Tol (4)). An alternative synthesis of complex 2 is the reaction of [MoO S ] with [Cu(SPh) ] . Similarly, [O MoS Cu(PPh )] (5), [O MoS Cu(dppe)] (dppe = 1,2-bis-(diphenylphosphino)ethane) (6), and [O MoS Cu(triphos)] (triphos = 1,1,1-tris[(diphenylphosphino)methyl]ethane) (7) were prepared from the reactions of [MoO S ] with the Cu(I) phosphine complexes. Treatment of 1, 2, 4, or 5 with dithiols (1,2-(SH) C H , 1,2-(SH) C H -3,6-Cl , and 1,2-(SH) C H ), in acetonitrile, leads to the replacement of a molybdenum-bound oxo ligand to yield [(dithiolate)Mo(O)S CuL] (L = CN, SAr; dithiolate = 1,2-S C H , 1,2-S C H -3,6-Cl , or 1,2-S C H ) (8-13) or [(1,2-S C H )Mo(O)S Cu(PPh )]- (14) complexes. © 2005 American Chemical Society. 2 2 2 2 2 2 2 2 3 2 2 3 2 2 2 2 2 2 2 6 4 2 6 2 2 2 2 4 2 2 6 4 2 6 2 2 2 2 4 2 6 4 2 3 2- 2- - 2- 2- 2- - - - 2- 2-