Al-Rasbi Nawal K, Tidmarsh Ian S, Argent Stephen P, Adams Harry, Harding Lindsay P, Ward Michael D
Department of Chemistry, University of Sheffield, Sheffield S3 7HF, UK.
J Am Chem Soc. 2008 Sep 3;130(35):11641-9. doi: 10.1021/ja803847w. Epub 2008 Aug 8.
Reaction of a tris-bidentate ligand L(1) (which can cap one triangular face of a metal polyhedron), a bis-bidentate ligand L(2) (which can span one edge of a metal polyhedron), and a range of M(2+) ions (M = Co, Cu, Cd), which all have a preference for six coordination geometry, results in assembly of the mixed-ligand polyhedral cages M12(mu(3)-L(1))4(mu-L(2))12. When the components are combined in the correct proportions [M(2+):L(1):L(2) = 3:1:3] in MeNO2, this is the sole product. The array of 12 M(2+) cations has a cuboctahedral geometry, containing six square and eight triangular faces around a substantial central cavity; four of the eight M3 triangular faces (every alternate one) are capped by a ligand L(1), with the remaining four M3 faces having a bridging ligand L(2) along each edge in a cyclic helical array. Thus, four homochiral triangular {M3(L(2))3}(6+) helical units are connected by four additional L(1) ligands to give the mixed-ligand cuboctahedral array, a topology which could not be formed in any homoleptic complex of this type but requires the cooperation of two different types of ligand. The complex Cd3(L(2))3(ClO4)4(MeCN)2(H2O)22, a trinuclear triple helicate in which two sites at each Cd(II) are occupied by monodentate ligands (solvent or counterions), was also characterized and constitutes an incomplete fragment of the dodecanuclear cage comprising one triangular {M3(L(2))3}(6+) face which has not yet reacted with the ligands L(1). (1)H NMR and electrospray mass spectrometric studies show that the dodecanuclear cages remain intact in solution; the NMR studies show that the Cd 12 cage has four-fold (D2) symmetry, such that there are three independent Cd(II) environments, as confirmed by a (113)Cd NMR spectrum. These mixed-ligand cuboctahedral complexes reveal the potential of using combinations of face-capping and edge-bridging ligands to extend the range of accessible topologies of polyhedral coordination cages.
三齿双齿配体L(1)（可覆盖金属多面体的一个三角形面）、双齿双齿配体L(2)（可跨越金属多面体的一条边）与一系列M(2+)离子（M = Co、Cu、Cd）反应，这些离子都倾向于六配位几何结构，结果形成了混合配体多面体笼M12(μ(3)-L(1))4(μ-L(2))12。当各组分在MeNO2中按正确比例[M(2+):L(1):L(2) = 3:1:3]混合时，这是唯一产物。12个M(2+)阳离子的阵列具有立方八面体几何结构，在一个较大的中心腔周围包含六个正方形面和八个三角形面；八个M3三角形面中的四个（每隔一个）被配体L(1)覆盖，其余四个M3面在每个边缘都有一个桥连配体L(2)，呈环状螺旋排列。因此，四个同手性三角形{M3(L(2))3}(6+)螺旋单元通过另外四个L(1)配体相连，形成混合配体立方八面体阵列，这种拓扑结构在任何此类纯配体配合物中都无法形成，而是需要两种不同类型配体的协同作用。配合物Cd3(L(2))3(ClO4)4(MeCN)2(H2O)22，一种三核三螺旋体，其中每个Cd(II)的两个位点被单齿配体（溶剂或抗衡离子）占据，也得到了表征，它构成了十二核笼的一个不完整片段，包含一个尚未与配体L(1)反应的三角形{M3(L(2))3}(6+)面。(1)H NMR和电喷雾质谱研究表明，十二核笼在溶液中保持完整；NMR研究表明，Cd 12笼具有四重（D2）对称性，可以确认有三种独立的Cd(II)环境，(113)Cd NMR谱也证实了这一点。这些混合配体立方八面体配合物揭示了使用封端面配体和桥连边配体的组合来扩展多面体配位笼可及拓扑结构范围的潜力。
