Cubes, squares, and books: a simple transition metal/bridging ligand combination can lead to a surprising range of structural types with the same metal/ligand proportions.
Cubes, squares, and books: a simple transition metal/bridging ligand combination can lead to a surprising range of structural types with the same metal/ligand proportions.
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DOI：
10.1021/ic901892y
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发表时间：
2009-11
影响因子：
4.6
通讯作者：
A. Najar;I. S. Tidmarsh;H. Adams;M. Ward
中科院分区：
文献类型：
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作者：
A. Najar;I. S. Tidmarsh;H. Adams;M. Ward
两个结构相关的桥连配体L（2, 6Py）和L（1, 3 Ph）与第一行过渡金属二价阳离子的反应产生了令人惊讶的多种结构，其中两个双齿螯合吡唑基-吡啶单元通过亚甲基间隔基连接到2，6-吡啶二基或1，3-苯二基中心基团。最常见的是八核配位笼[M（8）L（12）]X（16）[M = Co（II）或Zn（II）; X =高氯酸盐或四氟硼酸盐]，其中金属离子位于近似立方体的八个顶点中的每一个，并且一个双二齿桥接配体跨越每个边缘。fac和mer三螯合金属中心围绕反转中心的排列导致近似（非晶体学）S（6）对称性。在固态中观察到的另一种结构类型是六核配合物[Co（6）（L（13 Ph））（9）]（ClO（4））（12），其中六种金属离子呈矩形阵列（两排，每排三个），围绕中心Co-Co向量折叠，就像一本部分打开的书，每个金属-金属边缘除了两个最外面的金属-金属边缘外还含有一个桥连配体，由双螺旋阵列中的一对桥接配体跨越的金属边缘。我们观察到的最终结构类型是四核正方形[Ni（4）（L（26 Py））（6）]（BF（4））（8），其中四个Ni-Ni边缘由一个和两个桥接配体交替跨越，使得它有效地由两个通过额外的桥接配体交联的双核双螺旋组成。通过（1）H NMR和ES质谱研究，在许多情况下在溶液中观察到“立方体”和“书”形式之间的平衡，其因化合物而异。
Reaction of two structurally related bridging ligands L(26Py) and L(13Ph), in which two bidentate chelating pyrazolyl-pyridine units are connected to either a 2,6-pyridine-diyl or 1,3-benzene-diyl central group via methylene spacers, with first-row transition metal dications, results in a surprising variety of structures. The commonest is that of an octanuclear coordination cage [M(8)L(12)]X(16) [M = Co(II) or Zn(II); X = perchlorate or tetrafluoroborate] in which a metal ion is located at each of the eight vertices of an approximate cube, and one bis-bidentate bridging ligand spans each edge. The arrangement of fac and mer tris-chelate metal centers around the inversion center results in approximate (non-crystallographic) S(6) symmetry. Another structural type observed in the solid state is a hexanuclear complex [Co(6)(L(13Ph))(9)](ClO(4))(12) in which the six metal ions are in a rectangular array (two rows of three), folded about the central Co-Co vector like a partially open book, with each metal-metal edge containing one bridging ligand apart from the two outermost metal-metal edges which are spanned by a pair of bridging ligands in a double helical array. The final structural type we observed is a tetranuclear square [Ni(4)(L(26Py))(6)](BF(4))(8), with the four Ni-Ni edges spanned alternately by one and two bridging ligand such that it effectively consists of two dinuclear double helicates cross-linked by additional bridging ligands. A balance between the "cube" and "book" forms, which varied from compound to compound, was observed in solution in many cases by (1)H NMR and ES mass spectrometry studies.