Specific Incorporation of Chalcogenide Bridge Atoms in Molybdenum/Tungsten-Iron-Sulfur Single Cubane Clusters

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• 作者：Amit Majumdar ; R. H. Holm
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：November 7, 2011
• 年：2011
• 卷：50
• 期：21
• 页码：11242-11251
• 全文大小：1108K
• 年卷期：v.50,no.21(November 7, 2011)
• ISSN：1520-510X

文摘

An extensive series of heterometal-iron-sulfur single cubane-type clusters with core oxidation levels [MFe₃S₃Q]^3+,2+ (M = Mo, W; Q = S, Se) has been prepared by means of a new method of cluster self-assembly. The procedure utilizes the assembly system [(^tBu₃tach)M^VIS₃]/FeCl₂/Na₂Q/NaSR in acetonitrile/THF and affords product clusters in 30鈥?0% yield. The trisulfido precursor acts as a template, binding Fe^II under reducing conditions and supplying the MS₃ unit of the product. The system leads to specific incorporation of a 渭₃-chalcogenide from an external source (Na₂Q) and affords the products [(^tBu₃tach)MFe₃S₃QL₃]^{0/1鈥?/sup> (L = Cl鈥?/sup>, RS鈥?/sup>), among which are the first MFe₃S₃Se clusters prepared. Some 16 clusters have been prepared, 13 of which have been characterized by X-ray structure determinations including the incomplete cubane [(tBu₃tach)MoFe₂S₃Cl₂(渭₂-SPh)], a possible trapped intermediate in the assembly process. Comparisons of structural and electronic features of clusters differing only in atom Q at one cubane vertex are provided. In comparative pairs of complexes differing only in Q, placement of one selenide atom in the core increases core volumes by about 2% over the Q = S case, sets the order Q = Se > S in Fe-Q bond lengths and Q = S > Se in Fe-Q-Fe bond angles, causes small positive shifts in redox potentials, and has an essentially nil effect on 57Fe isomer shifts. Iron mean oxidation states and charge distributions are assigned to most clusters from isomer shifts. (tBu₃tach = 1,3,5-tert-butyl-1,3,5-triazacyclohexane)}