Sulfido-Bridged Dinuclear Molybdenum−Copper Complexes Related to the Active Site of CO Dehydrogenase:  [(dithiolate)Mo(O)S₂Cu(SAr)]^2- (dithiolate = 1,2-S₂C₆H₄, 1,2-S₂C₆H₂-3,6-Cl₂, 1,2-S₂C₂H₄)

Abstract

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)2C6H4, 1,2-(SH)2C6H2-3,6-Cl2, and 1,2-(SH)2C2H4), 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-Cl2, or 1,2-S2C2H4) (8-13) or [(1,2-S2C6H4)Mo(O)S2Cu(PPh3)]- (14) complexes.

Biomimetic Chemistry of Iron, Nickel, Molybdenum, and Tungsten in Sulfur-Ligated Protein Sites

“…While this complex lacks dithiolate binding simulating the cofactor ligand, it provides another example of the utility of the hydrotris(pyrazolyl)borate ligand platform in stabilizing a structural element of a molybdoenzyme site. A second relevant reaction affords the square pyramidal Mo VI complex 49 that incorporates the enzyme site features of an apical oxo atom, basal dithiolate coordination, and basal sulfido coordination to Cu I (85). However, it departs from 46 with two sulfido ligands which form mutually supported bridges to Cu I .…”

Synthesis and characterization of a binuclear copper(II) complex [Cu(H2slox)]2 from polyfunctional disalicylaldehyde oxaloyldihydrazone and its heterobinuclear copper(II) and molybdenum(VI) complexes

“…Molybdenum ions show antagonistic function with regard to copper in humans and animals [6][7][8][9]. Molybdenum-copper complexes or tungstencopper complexes combining polyfunctional ligands constitute an interesting system of research due to their diverse structural chemistry [10,11] and their relevance to biological systems [12,13]. Besides such importance of copper either alone or in combination with molybdenum in biological system, copper plays a significant role in combination with other metals such as zinc and iron in the active sites of several enzymes.…”

Synthetic reactions and coordination modes of ruthenium complexes with tris(mercaptomethimazolyl)borate ligands

“…Since the hydrotris(mercaptoimidazolyl)borate (Tm R ), as a new class of tripodal ligands somewhat analogous to the well established Tp R , was first reported by Reglinski and co-workers in 1996 [5,6], a wide variety of complexes with transition metals of the Tm R s have attracted an intense interest because sulfur-ligated transition metal centers are also abundant in enzymes such as nitrogenase, hydrogenase, and carbon monoxide dehydrogenase, and the modeling of these active sites has been the focus of our attention [7][8][9][10][11]. As known, an important property of the Tm R ligands is the delocalized anionic charge on the thioimidazole groups, which brings about the thiolate-like character of the thioimidazole sulfurs, however, there is a fundamental structural difference between the Tp R and Tm R ligands in that the number of atoms linking the boron atoms in each arm of the tripod is increased by one (N) in Tp R to two (NAC) in the Tm R ligand [12].…”

“…As known, an important property of the Tm R ligands is the delocalized anionic charge on the thioimidazole groups, which brings about the thiolate-like character of the thioimidazole sulfurs, however, there is a fundamental structural difference between the Tp R and Tm R ligands in that the number of atoms linking the boron atoms in each arm of the tripod is increased by one (N) in Tp R to two (NAC) in the Tm R ligand [12]. It might have been presumed that the Tm R ligand would simply serve as a hybrid between the facially tridentate Tp R and 1,4,7-trithiacyclononane ( [9] aneS 3 ) ligands, the former providing a ''hard" anionic N 3 donor set while the latter provides a ''soft" neutral S 3 set [12].…”