847830-75-5Relevant academic research and scientific papers
On [Fe4S4]2+-(μ2-SR)-M II bridge formation in the synthesis of an A-cluster analogue of carbon monoxide dehydrogenase/acetylcoenzyme A synthase
Rao, P. Venkateswara,Bhaduri, Sumit,Jiang, Jianfeng,Hong, Daewon,Holm
, p. 1933 - 1945 (2007/10/03)
The construction of a synthetic analogue of the A-cluster of carbon monoxide dehydrogenase/ acetylcoenzyme synthase, the site of acetylcoenzyme A formation, requires as a final step the formation of an unsupported [Fe 4S4]-(μ2-SR)-NiII bridge to a preformed cluster. Our previous results (Rao, P. V.; Bhaduri, S.; Jiang, J.; Holm, R. H. Inorg. Chem. 2004, 43, 5833) and the work of others have addressed synthesis of dinuclear complexes relevant to the A-cluster. This investigation concentrates on reactions pertinent to bridge formation by examining systems containing dinuclear and mononuclear NiII complexes and the 3:1 site-differentiated clusters [Fe4S4(LS3) L′]2- (L′ = TfO- (14), SEt (15)). The system 14/[{Ni(LO-S2N2)}M(SCH2CH 2PPh2)]+ results in cleavage of the dinuclear complex and formation of [{Ni(LO-S2N2)}-Fe 4S4(LS3)]- (18), in which the NiII complex binds at the unique cluster site with formation of a Ni(μ2-SR)2Fe bridge rhomb. Cluster 18 and the related species [{Ni(phma)}Fe4S4(LS3)]3- (19) are obtainable by direct reaction of the corresponding cis-planar Ni II-S2N2 complexes with 14. The mononuclear complexes [M(pdmt)(SEt)]- (M = NiII, PdII) with 14 in acetonitrile or Me2SO solution react by thiolate transfer to give 15 and [M2(pdmt)2]. However, in dichloromethane the NiII reaction product is interpreted as [{Ni(pdmt)(μ2- SEt)}Fe4S4(LS3)]2- (20). Reaction of Et3NH+ and 15 affords the double cubane [{Fe 4S4(LS3)}2(μ2-SEt)] 3- (21). Cluster 18 contains two mutually supportive Fe-(μ2-SR)-NiII bridges, 19 exhibits one strong and one weaker bridge, 20 has one unsupported bridge (inferred from the 1H NMR spectrum), and 21 has one unsupported Fe-(μ2-SR)-Fe bridge. Bridges in 18, 19, and 21 were established by X-ray structures. This work demonstrates that a bridge of the type found in the enzyme A-clusters is achievable by synthesis and implies that more stable, unsupported single thiolate bridges may require reinforcement by an additional covalent linkage between the Fe4S4 and nickel-containing components. (LS3 = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p- tolylthio)benzene(3-); LO-S2N2 = N,N′-diethyl-3,7-diazanonane-1,9-dithiolate(2-); pdmt = pyridine-2,6-methanedithiolate(2-); phma = N,N′-1,2-phenylenebis(2- acetylthio)-acetamidate(4-); TfO = triflate.).
