Effective Coordination Control by Utilizing the Cavity of Calixarenes

杯芳烃是一种用途广泛的配体，不仅具有两种不同类型的配位，即酚氧基和芳环，而且还具有包裹体位置(空腔)。然而，过渡金属络合物在杯芳烃空腔内的配位化学仍有待探索。本文研究了金属中心位于杯[4]芳烃空腔内的两个系列杯[4]芳烃配合物，发现杯[4]芳烃与[CpRu(CH_3CN)_3]PF_6在Et_3N存在下反应，以较好的产率得到了Ru-芳烃类配合物[CpRu{杯[4]-(0)(OH)_3}](1)。配合物1的X-射线衍射研究表明，CpRu碎片存在于杯[4]芳烃配体的空腔中，1的Cp质子在~1H核磁共振中表现出特征的高场位移。这一事实与Cp*Ru片段与杯[4]芳烃的络合形成了鲜明的对比，在杯[4]芳烃中，金属中心结合在ph…的外表面更多的烯醇环(络合物2)和1可以被视为“自包合体”产物。在配合物1中进一步引入Cp*Ru片段得到[(CpRu)(Cp*Ru){杯[4]-(0)(OH)_3}](3)的内外异构体，而在配合物2中引入CpRu则得到其内外异构体。这些结果表明，CpRu部分首先是杯芳烃分子外表面的配位，然后杯芳烃骨架的环反转提供了内部配位产物。另一方面，当[Ph_4P][ReO_2{p-tBU-杯[4]-(0)_4}](4)用各种阳离子过渡金属络合物ML处理时，苯氧桥联的Re-M络合物[ReO_2{p-TBU-杯[4]-(0)_4}ML](5a，ML=铜(NCMe)；5b，Ag(Me2C0)；5C，Au(Ppha)；5d，Rh(Cod))，产率较高。配合物5a的异双核位于空腔内，表现出独特的光谱和化学行为。例如，化合物5a进行选择性的烯烃掺入，而化合物5d进行溶剂依赖的异构化为π-芳烃类型的区域异构体。较少

Calixarenes are known to serve as a versatile ligand not only with two distinct types of coordination sites, phenolic oxygens and arene rings, but also with an inclusion site (cavity). However, coordination chemistry of transition-metal complexes inside the cavity of calixarenes still remains to be explored. In this study we have investigated two series of calix[4]arene complexes in which the metal centers are located inside the cavity of calix[4]arenes.The reaction of calix[4]arene with [CpRu(CH_3CN)_3]PF_6 in the presence of Et_3N has been found to give the ruthenium-arene type complex [CpRu{calix[4]-(0)(OH)_3}] (1)in good yield. An X-ray diffraction study of complex 1 has revealed that the CpRu+ fragment resides in the cavity of the calix[4]arene ligand, and the Cp protons of 1 exhibit characteristic high-field shift in the ^1H NMR. This fact makes a sharp contrast to the complexation of a Cp*Ru+ fragment with calix[4]arene where the metal center is bound at the outside face of a ph … More enolic ring(complex 2), and 1 can be viewed as a "self-inclusion" product. Further introduction of a Cp*Ru+ fragment into complex 1 gives rise to the inside-outside isomer of [(CpRu)(Cp*Ru){calix[4]-(0)(OH)_3}]+ (3), while introduction of a CpRu+ into 2 leads to its outside-outside isomer. These results indicates that the CpRu+ moiety is first coordinates at the outside face of a calixarene molecule, and then the ring inversion of the calixarene skeleton affords the inside coordination product.On the other hand, when [Ph_4P][ReO_2{p-tBu-calix[4]-(0)_4}] (4)is treated with a variety of cationic transition metal complex ML+, the phenoxo-bridged Re-M complexes [ReO_2{p-tBu-calix[4]-(0)_4}ML] (5a, ML = Cu(NCMe); 5b, Ag(Me2C0); 5c, Au(Ppha); 5d, Rh(cod)) can be obtained in good yield. The heterodinuclear core of complex 5a is located inside the cavity and have revealed to show unique spectral and chemical behaviors. For example, complex 5a undergoes selective alkyne incorporation, while complex 5d undergoes solvent-dependent isomerization to π-arene type regioisomers. Less