Edge-bridged Mo2Fe6S8 to PN-type Mo2Fe6S9 cluster conversion:: Structural fate of the attacking sulfide/selenide nucleophile
Edge-bridged Mo2Fe6S8 to PN-type Mo2Fe6S9 cluster conversion:: Structural fate of the attacking sulfide/selenide nucleophile
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DOI：
10.1021/ja063604x
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发表时间：
2006-09-13
影响因子：
15
通讯作者：
Holm, R. H.
中科院分区：
文献类型：
--
作者：
Berlinguette, Curtis P.;Holm, R. H.
边桥双立方烷簇合物[（Tp）（2）M_2Fe_6S_8（PEt_3）（4）]（1; Tp =氢化三吡唑硼酸酯（1-））与硫化氢反应得到簇合物[（Tp）（2）M_2Fe_6S_9（SH）（2）]（3-，4-）（M = Mo（2），V），它们是固氮酶P-N簇合物的第一个拓扑结构类似物。合成反应是核转化的一个实例，导致转化M2 Fe 6（mu（3）-S）（6）（mu（4）-S）（2）（C-i）-> M2 Fe 6（mu（2）-S）（2）（mu（3）-S）（6）（mu（6）-S）（C-2 v），其反应途径未知。P-N型簇合物最显著的结构特征是mu（6）-S原子，其在簇合物的两个MFe 3S 3立方体半部中桥接六个铁原子。核心转换中的初始问题是μ（6）-S原子的起源。在1/SeH-/L-乙腈体系中，利用SeH-替代SH-，合成了一系列硒化物簇合物[（Tp）（2）Mo 2Fe 6S 8 SeL 2]（3-）（L- = SH-（4），SeH-（5），EtS-（6），CN-（7））. 4和6的电喷雾质谱显示每个簇中包含一个Se原子，4-7的H-1 NMR光谱和晶体学精修表明该原子在两个mu（2）-S/Se位置上是无序的。由2和5分别制备了簇合物{[（Tp）（2）Mo 2Fe 6S 9]（mu（2）-S）}（2）（5-）（8）和{[（Tp）（2）Mo 2Fe 6S 8 Se]（mu（2）-Se）}25-（9），并证明是同构的。它们由两个μ（2）-S或μ（2）-Se原子桥连的P-N型团簇单元组成。可以得出结论，在2的制备中，攻击亲核试剂的可能结构命运是作为mu（2）-S原子，并且产物簇的mu（3）-S和mu（6）-S原子来自前体簇1。在P-N型簇合成过程中簇分裂是不可能的。
Reaction of the edge-bridged double cubane cluster [(Tp)(2)M2Fe6S8(PEt3)(4)] (1; Tp = hydrotris(pyrazolyl)borate(1-)) with hydrosulfide affords the clusters [(Tp)(2)M2Fe6S9(SH)(2)](3-,4-) (M = Mo (2), V), which have been established as the first structural (topological) analogues of the P-N cluster of nitrogenase. The synthetic reaction is an example of core conversion, resulting in the transformation M2Fe6(mu(3)-S)(6)(mu(4)-S)(2)(C-i) -> M2Fe6(mu(2)-S)(2)(mu(3)-S)(6)(mu(6)-S) (C-2v), the reaction pathway of which is unknown. The most prominent structural feature of P-N-type clusters is the mu(6)-S atom, which bridges six iron atoms in two MFe3S3 cuboidal halves of the cluster. The initial issue in core conversion is the origin of the mu(6)-S atom. Utilizing SeH- as a surrogate reactant for SH- in the system 1/SeH-/L- in acetonitrile, a series of selenide clusters [(Tp)(2)Mo2Fe6S8SeL2](3-) (L- = SH- (4), SeH- (5), EtS- (6), CN- (7)) was prepared. The electrospray mass spectra of 4 and 6 revealed inclusion of one Se atom in each cluster, and H-1 NMR spectra and crystallographic refinements of 4-7 indicated that this atom was disordered over the two mu(2)-S/Se positions. The clusters {[(Tp)(2)Mo2Fe6S9](mu(2)-S)}(2)(5-) (8) and {[(Tp)(2)Mo2Fe6S8Se](mu(2)-Se)}25- ( 9) were prepared from 2 and 5, respectively, and shown to be isostructural. They consist of two P-N-type cluster units bridged by two mu(2)-S or mu(2)-Se atoms. It is concluded that, in the preparation of 2, the probable structural fate of the attacking nucleophile is as a mu(2)-S atom, and that the mu(3)-S and mu(6)-S atoms of the product cluster derive from precursor cluster 1. Cluster fragmentation during P-N-type cluster synthesis is unlikely.