Self-Assembled E2L3 Cryptands (E = P, As, Sb, Bi): Transmetalation, Homo- and Heterometallic Assemblies, and Conformational Isomerism
Self-Assembled E2L3 Cryptands (E = P, As, Sb, Bi): Transmetalation, Homo- and Heterometallic Assemblies, and Conformational Isomerism
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DOI：
10.1021/ic1012186
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发表时间：
2010-11-01
影响因子：
4.6
通讯作者：
Johnson, Darren W.
中科院分区：
文献类型：
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作者：
Cangelosi, Virginia M.;Carter, Timothy G.;Johnson, Darren W.
通过磷属卤化物与二硫纶配体的自组装或重金属同系物的直接金属转移反应，合成了一系列含15族元素的均三（E_2L_3，E = P，As，Sb，Bi）和异金属（AsSbL_3，AsBiL_3，PSbL_3）超分子穴状配体.单晶X-射线衍射结构表征表明，氮族元素的身份对E-S键长和S-E-S键角有显著影响。1H-1 NMR光谱表明，homopolysaccharands在溶液中是动态的：令人惊讶的是，一个配体“翻转”，扰动的C-3对称性的复杂的，并给出一个新的不对称构象。密度泛函理论计算上进行的对称和不对称的穴状配体的构象，并通过NMR光谱观察到的能量进行了比较。结果表明，不对称穴配体相对于其对称构象的稳定性随第15族元素尺寸的增大而增大。最后，据报道，如果在自组装过程中存在两种金属，则形成异金属穴状配体。这些超分子穴状配体让人联想到它们的有机类似物，但它们是由自组装过程而不是逐步合成的。令人惊讶的是，它们具有构象异构性，并在它们的反应性中表现出动态金属转移，这提供了获得以其他方式无法获得的组装体的途径。
series of Group 15-containing homometallic (E2L3, E = P, As, Sb, Bi) and heterometallic (AsSbL3, AsBiL3, PSbL3) supramolecular cryptands were prepared by the self-assembly of pnictogen halides with dithiolate ligand or by direct transmetalation from a heavier congener. Structural characterization by single crystal X-ray diffraction shows that the E-S bond distances and S-E-S bond angles are significantly affected by the identity of the pnictogen. H-1 NMR spectroscopy reveals that the homometallic cryptands are dynamic in solution: surprisingly one ligand "flips", perturbing the C-3 symmetry of the complex and giving a new asymmetric conformer. Density functional theory calculations were carried out on both the symmetric and the asymmetric conformations of the cryptands, and the energies were compared to those observed by NMR spectroscopy. It was found that the relative stability of the asymmetric cryptand to its symmetric conformer increases with increasing size of the Group 15 element. Finally, it is reported that if two metals are present during the self-assembly process, heterometallic cryptands form. These supramolecular cryptands are reminiscent of their organic analogues, but result from a self-assembly process rather than a stepwise synthesis. Surprisingly, they possess conformational isomerism and exhibit dynamic transmetalation in their reactivity which provides access to otherwise unattainable assemblies.