Ramaswamy Kannan, Tulsky Eric G, Long Jeffrey R, Kao Jeff L-F, Hayes Sophia E
Department of Chemistry and Center for Materials Innovation, Washington University, St. Louis, MO 63130, USA.
Inorg Chem. 2007 Feb 19;46(4):1177-86. doi: 10.1021/ic061571g.
We have investigated rarely observed 77Se J-couplings (spin-spin couplings) in the mixed-metal face-capped octahedral clusters [Re5OsSe8(CN)6]3- and [Re4Os2Se8(CN)6]2- at natural abundance. To the best of our knowledge, these are the first observations of Se-Se spin-spin interactions between mu3-Se sites, important for stereochemical assignments in hexarhenium analogues, Chevrel phase materials, and similar cluster materials. NMR techniques such as COSY, INADEQUATE, and 2D J-resolved spectroscopy have been used in conjunction to study these interactions. The two isomers (cis and trans) of [Re4Os2Se8(CN)6]2- were distinguishable, and selective isotopic labeling of [Re5OsSe8(CN)6]3- with 13CN ligands enabled resonances to be assigned by observing the 2J (Se-M-C) couplings. For [Re5OsSe8(CN)6]3-, two different 2J (Se-M-Se) couplings were measurable on a single cluster, and these are related to one another through spin-spin interactions across a face diagonal or along an edge of the cube of inner selenium ligands. A rigorous analysis based on combinatorial math has been invoked to assign the couplings on the basis of the probability of multiple-spin interactions. The face diagonal association is found to result in a J-coupling interaction larger in magnitude than that from coupling along an edge of the cube-information critical for making stereochemical assignments of selenium sites.
我们研究了在天然丰度下，混合金属面封端八面体簇合物[Re5OsSe8(CN)6]3-和[Re4Os2Se8(CN)6]2-中罕见观测到的77Se J耦合（自旋-自旋耦合）。据我们所知，这些是首次观测到μ3-Se位点之间的Se-Se自旋-自旋相互作用，这对于六铼类似物、 Chevrel相材料及类似簇合物材料的立体化学归属很重要。已结合使用COSY、INADEQUATE和二维J分辨光谱等核磁共振技术来研究这些相互作用。[Re4Os2Se8(CN)6]2-的两种异构体（顺式和反式）是可区分的，用13CN配体对[Re5OsSe8(CN)6]3-进行选择性同位素标记，通过观测2J(Se-M-C)耦合来确定共振。对于[Re5OsSe8(CN)6]3-，在单个簇合物上可测量到两种不同的2J(Se-M-Se)耦合，它们通过跨越内硒配体立方体的面角对角线或沿边的自旋-自旋相互作用相互关联。已采用基于组合数学的严格分析，根据多自旋相互作用的概率来确定耦合。发现面角对角线关联导致的J耦合相互作用比沿立方体边的耦合作用大——这一信息对于确定硒位点的立体化学至关重要。
