title: Sulfur ligand substitution at the nickel(II) sites of cubane-type and cubanoid NiFe3S4 clusters relevant to the C-clusters of carbon monoxide dehydrogenase.
abstract: Substitution reactions at the nickel site of the cubane-type cluster [(Ph3P)NiFe3S4(LS3)]2- (2) have been investigated in the course of a synthetic approach to the C-clusters of CODH. Reaction of 2 with RS- or toluene-3,4-dithiolate affords [(RS)NiFe3S4(LS3)]3- (R = Et (5), H (6)) or [(tdt)NiFe3S4(LS3)]3- (7), demonstrating that anionic sulfur ligands can be bound at the NiII site. Clusters 5 and 6 contain tetrahedral Ni(micro3-S)3(SR) sites. Cluster 7 is of particular interest because it includes a cubanoid NiFe3(micro2-S)(micro3-S)3 core and an approximately planar Ni(tdt)(micro3-S)2 unit. The cubanoid structure is found in all C-clusters, and an NiS4-type unit has been reported in C. hydrogenoformans CODH. Clusters 5/6 are formulated to contain the core [NiFe3S4]1+ identical with Ni2+ (S = 1) + [Fe3S4]1- (S = 5/2) and 7 the core [NiFe3S4]2+ identical with Ni2+ (S = 0) + [Fe3S4]0 (S = 2) on the basis of structure, 57Fe isomer shifts, and 1H NMR isotropic shifts. Also reported are [(EtS)CuFe3S4(LS3)]3- (9) and [Fe4S4(LS3)(tdt)]3- (11). The structures of 5-7, 9, and 11 are presented. Cluster 11, with a five-coordinate Fe(tdt)(micro3-S)3 site, provides a clear structural contrast with 7, which is currently the closest approach to a C-cluster but lacks the exo iron atom found in the NiFe4S4,5 cores of the native clusters. (CODH = carbon monoxide dehydrogenase, LS3 = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzene(3-), tdt = toluene-3,4-dithiolate).
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Jibin
authors.initials: J
authors.lastname: Sun
authors.forename: Christian
authors.initials: C
authors.lastname: Tessier
authors.forename: R H
authors.initials: RH
authors.lastname: Holm
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D002244:Carbon / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000378:metabolism*; D009532:Nickel / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010459:Peptococcaceae / Q000201:enzymology; D013455:Sulfur / Q000737:chemistry*
chemical_list: D008024:Ligands; D009097:Multienzyme Complexes; D009942:Organometallic Compounds; D013455:Sulfur; D002244:Carbon; D009532:Nickel; D000445:Aldehyde Oxidoreductases; C019823:carbon monoxide dehydrogenase