부산대학교 도서관

Synthesis of an analogue of the C-cluster of C. hydrogenoformans carbon monoxide dehydrogenase requires formation of a planar Ni∥ site and attachment of an exo iron atom in the core unit NiFe4S5. The first objective has been achieved by two reactions: (i) displacement of Ph3P or ButNC at tetrahedral Ni∥ sites of cubane-type [NiFe3S4]+ clusters with chelating diphosphines, and (ii) metal atom incorporation into a cuboidal [Fe3S4]0 cluster with a M0 reactant in the presence of bis(1,2-dimethylphosphino)ethane (dmpe). The isolated product clusters [(dmpe)MFe3S4(LS3)]2- (M = Ni∥ (9), Pd∥ (12), Pt∥ (13); LS3 = 1,3,5- tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzene(3-)) contain the cores [MFe3(μ2-S*)(μ3-S)3]+ having planar M∥P2S2 sites and variable nonbonding M┅S* distances of 2.6–3.4 Å. Reaction (i) involves a tetrahedral → planar Ni∥ structural change between isomeric cubane and cubanoid [NiFe3S4]+ cores. Based on the magnetic properties of 12 and earlier considerations, the S = 5/2 ground state of the cubanoid cluster arises from the [Fe3S4] fragment, whereas the S = 3/2 ground state of the cubane cluster is a consequence of antiferromagnetic coupling between the spins of Ni2+ (S = 1) and [Fe3S4]. Other substitution reactions of [NiFe3S4]+ clusters and 1:3 site-differentiated [Fe4S4]2+ clusters are described, as are the structures of 12, 13, [(Me3P)NiFe3S4(LS3)]2-, and [Fe4S4(LS3)L']2- (L' = Me2NC2H4S, Ph2P(O)C2H4S-). This work significantly expands our initial report of cluster 9 (Panda et al. J. Am. Chem. Soc. 2004, 126, 6448–6459) and further demonstrates that a planar M∥ site can be stabilized within a cubanoid [NiFe3S4]+ core. [ABSTRACT FROM AUTHOR]