A Continuous Symmetry Measure of [4Fe-4S]+ Core Distortions and Analysis of Supramolecular Synthons in Crystal Structures of (Et4N)3[Fe4S4Cl4] • Et4NCl at 100 and 295 K
A Continuous Symmetry Measure of [4Fe-4S]+ Core Distortions and Analysis of Supramolecular Synthons in Crystal Structures of (Et4N)3[Fe4S4Cl4] • Et4NCl at 100 and 295 K
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DOI：
10.1021/ic801533q
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发表时间：
2008-12-15
影响因子：
4.6
通讯作者：
Uddin, Mohammad
中科院分区：
文献类型：
--
作者：
Hagen, Karl S.;Uddin, Mohammad
根据连续对称性测度（CSM，S（T（d）分析了合成模型的[4Fe-4S]（+）核从T（d）对称性的畸变，这些畸变与小分子结构晶体工程中常见的超分子合成子术语中的晶格效应有关。在低温下观察到的从理想化的Td对称性到D（2d）的小的四重压缩归因于环境因素。通过用NaHS处理FeCl（2）或用Et（4）NSH和碱处理（Et（4）N）（2）[FeCl（4）]，以中等产率制备了气敏还原簇合物（Et（4）N）（3）[Fe（4）S（4）Cl（4）]中心点Et（4）NCl（1）复盐的组成变化的同晶系列的新成员.晶体与相应的HS（-）连接簇同晶。晶体数据：在100 K时，P（4）/bar 2（1）c，Z = 2，a = B = 12.2550（4），c = 16.278（1）埃;在295 K时，a = B = 12.385（1），c = 16.344（2）埃。晶体学强加的S（4）对称性与空间无关的配体提供了一个更好的视图的核心结构的内在几何形状。卤素离子的共结晶提供了比较三种类型的弱C-H键的机会。X氢键，或氢桥，在相同晶格内的四烷基铵阳离子和阴离子之间。C中心点Cl（-）距离（100 K时的3.590和3.634分别增加到295 K时的3.616和3.655埃）几乎与温度无关，表明存在硬氢桥，而C中心点Cl-Fe距离在100 K下为3.702-3.718埃，但在室温下为3.753-3.764埃，表明氢桥较软。类似的趋势适用于两组C中心点中心点mu（3）-S距离（在100 K下为3.766-3.788埃和3.594-3.604埃，在室温下为3.821-3.848埃和3.614-3.676埃）。较长的氢桥比较短的氢桥（134度）更线性（170度）。团簇的核心畸变与团簇周围阳离子的空间分布有关。
Distortions of the [4Fe-4S](+) cores of synthetic models from T(d) symmetry are analyzed in terms of the continuous symmetry measures (CSM, S(T(d))), and these are related to lattice effects in terms of the supramolecular synthon terminology common to crystal engineering of small molecule structures. The small tetragonal compression to D(2d) from idealized Td symmetry observed at low temperature is attributed to environmental factors. New members of the isomorphous series of compositional variations of double salts of the air-sensitive reduced cluster (Et(4)N)(3)[Fe(4)S(4)Cl(4)] center dot Et(4)NCl (1) are prepared in modest yield by treatment of FeCl(2) with NaHS, or (Et(4)N)(2)[FeCl(4)] with Et(4)NSH and a base. The crystals are isomorphous with the corresponding HS(-) ligated cluster. Crystal data: tetragonal, P (4) over bar2(1)c, Z = 2, a = b = 12.2550 (4), c = 16.278 (1) angstrom at 100 K, and a = b = 12.385 (1), c = 16.344 (2) angstrom at 295 K. The crystallographically imposed S(4) symmetry obtained with sterically unincumbering ligands affords a better view of the intrinsic geometry of the core structure. The cocrystallization of the halide ion affords the opportunity to compare three types of weak C-H... X hydrogen bonds, or hydrogen bridges, between tetraalkylammonium cations and anions within the same crystal lattice. The C center dot center dot center dot Cl(-) distances (3.590 and 3.634 at 100 K increase to 3.616 and 3.655 angstrom, respectively, at 295 K) are virtually temperature independent, indicative of hard hydrogen bridges, whereas the C center dot center dot center dot Cl-Fe distances are 3.702-3.718 angstrom at 100 K but are 3.753-3.764 angstrom at room temperature, suggesting a softer hydrogen bridge. A similar trend applies to the two sets of C center dot center dot center dot mu(3)-S distances (3.766-3.788 angstrom and 3.594-3.604 angstrom at 100 K and 3.821-3.848 angstrom and 3.614-3.676 angstrom at room temperature). The longer hydrogen bridges are more linear (170 degrees) than the shorter ones (134 degrees). The core distortions are correlated with spatial distribution of cations around the clusters.