title: Rearrangement of symmetrical dicubane clusters into topological analogues of the P cluster of nitrogenase: nature's choice?
abstract: Reaction schemes have been developed that lead to clusters having the topology of the PN cluster of nitrogenase. The single cubane clusters [(Tp)MFe3S4Cl3]z (M = Mo, z = 1-; M = V, z = 2-) react with PEt3 to give [(Tp)MFe3S4(PEt3)3]1+, which are reduced to the neutral edge-bridged double cubanes [(Tp)2M2Fe6S8(PEt3)4] with highly reduced (2[MFe3S4]1+) cores. Reaction of these clusters in acetonitrile with (Et4N)(HS) results in the formation of [(Tp)2Mo2Fe6S9(SH)2]3- and [(Tp)2V2Fe6S9(SH)2]4-. X-ray structures of the Et4N+ salts reveal the bridging pattern M2Fe6(mu2-S)2(mu3-S)6(mu6-S) in which two cuboidal MFe3(mu3-S)3 units share the common bridge atom mu6-S and are externally bridged by two mu2-S atoms. The M sites possess trigonal octahedral, and the Fe sites, distorted tetrahedral coordination. Hydrosulfide ligands and sulfide atoms simulate terminal cysteinate ligation and mu2 bridges, respectively, in the protein-bound cluster Fe8S7(mu2-SCys)2(SCys)4. The synthetic clusters have the same bridging pattern as the PN cluster and approach congruency with it. These clusters are the first molecular topological analogues of a PN cluster. Like the latter, they are substantially reduced (majority of Fe(II)).
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Yugen
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jing-Lin
authors.initials: JL
authors.lastname: Zuo
authors.forename: Hong-Cai
authors.initials: HC
authors.lastname: Zhou
authors.forename: R H
authors.initials: RH
authors.lastname: Holm
mesh_terms: D040761:Biomimetic Materials / Q000138:chemical synthesis / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D008982:Molybdenum / Q000737:chemistry; D009591:Nitrogenase / Q000737:chemistry*; D010084:Oxidation-Reduction; D013455:Sulfur / Q000737:chemistry; D014639:Vanadium / Q000737:chemistry
chemical_list: D007506:Iron-Sulfur Proteins; D014639:Vanadium; D013455:Sulfur; D008982:Molybdenum; D007501:Iron; D009591:Nitrogenase