Molybdenum-iron-sulfur clusters of nuclearities eight and sixteen, including a topological analogue of the P-cluster of nitrogenase.
Molybdenum-iron-sulfur clusters of nuclearities eight and sixteen, including a topological analogue of the P-cluster of nitrogenase.
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DOI：
10.1021/ic000617h
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发表时间：
2001-01
影响因子：
4.6
通讯作者：
Frank E. Osterloh;Catalina Achim;Richard H. Holm
中科院分区：
文献类型：
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作者：
Frank E. Osterloh;Catalina Achim;Richard H. Holm
研究了边桥双立方烷簇合物[（Cl_4cat）_2（Et_3P）_2 Mo_2Fe_6S_8（PEt_3）_4]（1）在还原条件下的转化，作为合成固氮酶簇合物的途径。簇1是不同Mo-Fe-S簇类型的通用前体。在THF中的反应体系1/K（C14 H10）产生还原的簇合物[（Cl 4cat）2（Et 3 P）2 Mo 2Fe 6S 8（PEt 3）4]1-（2），其作为其结晶Et 4 N+盐保留了1的边桥结构。X射线结构和穆斯堡尔谱的结果表明，该化合物具有不对称的电子分布，具有局域的[MoFe 3S 4]2+，1+立方烷结构单元.在THF/乙腈中的12 K（C14 H10）/2 HS-体系得到[（Cl 4cat）4（Et 3 P）4 Mo 4Fe 12 S20 K3（DMF）]5-（3），其结构被确定为Ph 3 PMe+盐。簇合物由两个同构的Mo_2Fe_6S_9片段通过两个mu_2-S桥连接而成。三个钾离子结合在两个碎片之间。在每个片段中，铁原子存在于四面体FeS 4中，钼原子存在于八面体MoO 2 PS3配位单元中，并且两个MoFe 3（mu 3-S）3立方单元由共同的mu 6-S原子桥接。这些碎片具有理想的镜像对称性，并且与先前报道的高核性簇[（Cl 4cat）6（Et 3 P）6 Mo 6 Fe 20 S30]8-（4）（Osterloh，F.; Sanakis，Y.;斯台普斯河J.道：Münck，E.;霍尔姆河H. Angew.化学成分：国际英语版1999，38，2066）。根据整体形状、原子连通性和度量特征，Mo 2Fe 6S 9片段是PN（还原）状态下固氮酶P-簇的拓扑类似物。第三种簇合物类型是在生成2的反应体系中作为次要副产物形成的，晶体学鉴定为[（Cl 4cat）2（Et 3 P）2 Mo 2Fe 6S 8（PEt 3）4]4-，其核心由两个MoFe 3（mu 3-S）3立方体单元组成，由两个mu 2-S原子桥接并通过直接的Fe-Fe键连接。完整的结构细节和氧化还原性能的2和3的报告。
Transformations of the edge-bridged double cubane cluster [(Cl4cat)2(Et3P)2Mo2Fe6S8(PEt3)4] (1) under reducing conditions have been investigated as synthetic approaches to the clusters of nitrogenase. Cluster 1 is a versatile precursor to different Mo-Fe-S cluster types. The reaction system 1/K(C14H10) in THF yields the reduced cluster [(Cl4cat)2(Et3P)2Mo2Fe6S8(PEt3)4]1- (2), which as its crystalline Et4N+ salt retains the edge-bridged structure of 1. X-ray structural and Mössbauer spectroscopic results indicate an unsymmetrical electron distribution with localized [MoFe3S4]2+,1+ cubane-type units. The system 1/2K(C14H10)/2HS- in THF/acetonitrile affords [(Cl4cat)4(Et3P)4Mo4Fe12S20K3(DMF)]5- (3), whose structure was determined as the Ph3PMe+ salt. The cluster consists of two isostructural Mo2Fe6S9 fragments connected by two mu 2-S bridges. Three potassium ions are bound between the two fragments. In each fragment, the iron atoms are present in tetrahedral FeS4 and the molybdenum atoms in octahedral MoO2PS3 coordination units, and two MoFe3(mu 3-S)3 cuboidal units are bridged by a common mu 6-S atom. The fragments have idealized mirror symmetry and are isostructural with two of the fragments present in the previously reported high-nuclearity cluster [(Cl4cat)6(Et3P)6Mo6Fe20S30]8- (4) (Osterloh, F.; Sanakis, Y.; Staples, R. J.; Münck, E.; Holm, R. H. Angew. Chem., Int. Ed. Engl. 1999, 38, 2066). On the basis of overall shape, atom connectivities, and metric features, the Mo2Fe6S9 fragment is a topological analogue of the P-cluster of nitrogenase in the PN (reduced) state. A third cluster type, formed as a minor byproduct in the reaction system leading to 2, was crystallographically identified as [(Cl4cat)2(Et3P)2Mo2Fe6S8(PEt3)4]4-, whose core is made up of two MoFe3(mu 3-S)3 cuboidal units bridged by two mu 2-S atoms and connected by a direct Fe-Fe bond. Full structural details and the redox properties of 2 and 3 are reported.