Metal Ion Incorporation Reactions of the Cluster [Fe3S4(LS3)]3-, Containing the Cuboidal [Fe3S4]0 Core

详细信息    查看全文

• 作者：Jian Zhou ; James W. Raebiger ; Charles A. Crawford ; and R. H. Holm
• 刊名：Journal of the American Chemical Society
• 出版年：1997
• 出版时间：July 9, 1997
• 年：1997
• 卷：119
• 期：27
• 页码：6242 - 6250
• 全文大小：335K
• 年卷期：v.119,no.27(July 9, 1997)
• ISSN：1520-5126

文摘

The frequent occurrence of the cuboidal cluster[Fe₃S₄(S·Cys)₃] in avariety of proteins has promptedextensive investigation of its chemical and biological properties.The biological function remains in question, butthe cluster is known to sustain two reactions: (i) electron transfer,and (ii) heterometal ion incorporation. Therecent preparation of[Fe₃S₄(LS₃)]^3-(3) [Zhou, J.; Hu, Z.; Münck, E.; Holm, R. H.J. Am. Chem. Soc. 1996,118,1966] has permitted detailed structural, electronic, and reactivitycharacterization of the cuboidal[Fe₃S₄]⁰ oxidationstate (LS₃ =1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzene(3-).Redox properties(i) have been reported previously: here reaction type (ii), resultingin the formation of cubane-type MFe₃S₄clusters,has been investigated. Reaction of 3 with[M(PPh₃)₄]¹⁺ affords[(Ph₃P)MFe₃S₄(LS₃)]^2-(M = Cu (6), Ag (8)) while[(NC)M(PPh₃)₃] leads to[(NC)MFe₃S₄(LS₃)]^3-(M = Cu (7), Ag (9)). Treatment of3 with Tl(O₃SCF₃)yields[TlFe₃S₄(LS₃)]^2-(10). The fragment formalism {M¹⁺ +[Fe₃S₄]⁰} applies to6-10, which retain the S = 2groundstate of 3. Reaction of 3 with[M(PPh₃)₃Cl] yields[(Ph₃P)MFe₃S₄(LS₃)]^2-(M = Co (12), Ni (14)) ininner-sphereredox reactions. Clusters 12 (S = 1) and14 (S = ³/₂) areformulated as {M²⁺ +[Fe₃S₄]^1-};antiferromagneticcoupling of fragment spins gives rise to the indicated spin groundstates. The reactions (ii) are metal-ionincorporationprocesses, a new reaction type in Fe-S chemistry. Previously,all cubane-type MFe₃S₄ clusters had beensynthesizedby spontaneous self-assembly or reductive rearrangement reactions.Cluster 7 exhibits reversible oxidationandreduction reactions; it is the only cluster that forms a stableoxidized product containing the[Fe₃S₄]¹⁺ fragment.Allother clusters show a reversible reduction and an irreversible orquasireversible oxidation. Potentials of thesyntheticclusters are considered intrinsic to the various core units, being lessinfluenced by environmental factors than arethose in proteins. At parity of cluster charge and terminalligation, the potential order is M = Fe < Co < Ni andCo < Ni < Cu < Ag < Tl for the[MFe₃S₄]^2+,1+ and[MFe₃S₄]^1+,0 core redoxreactions. These orders are comparedwith those determined in proteins.