Macrocyclic Platforms for the Construction of Tetranuclear Oxo and Hydroxo Zinc Clusters
Macrocyclic Platforms for the Construction of Tetranuclear Oxo and Hydroxo Zinc Clusters
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DOI：
10.1021/om501244n
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发表时间：
2015-06-08
期刊：
影响因子：
2.8
通讯作者：
Love, Jason B.
中科院分区：
文献类型：
--
作者：
Cadenbach, Thomas;Pankhurst, James R.;Love, Jason B.
配体的设计，可以作为平台的控制，“自下而上”的过渡金属簇的合成是一个很有前途的方法来访问酶模拟和新的小分子反应化学。这种方法是通过两个隔室席夫碱杯吡咯（H4 L），通常作为双核配体的过渡金属的配位化学在这里举例说明。虽然H4 L和Zn{N（SiMe 3）（2）}（2）之间的反应形成预期的双核Zn“Pacman”络合物Zn-2（L），但与ZnEt 2的反应产生四核Zn烷基络合物Zn 4 Et 4（THF）（4）（L），其中由于大环平台的柔性而采用开放的“碗状”结构：这些四核配合物的水解反应的结果被发现依赖于大环空腔的大小，其中较小的大环有利于在Zn-4（mu（4）-O）Et-2（L）中形成氧代，较大的大环有利于完全水解形成氢氧桥连簇Zn-4（mu（2）-OH）（4）（L）.后一种络合物在高温下与二氧化碳反应，重整游离的大环H4 L并消除ZnCO 3。
The design of ligands that can act as platforms for the controlled; "bottom-up" synthesis of transition-metal clusters is a promising approach to accessing enzymatic mimics and new small-molecule reaction chemistry. This approach is exemplified here through the coordination chemistry of two compartmental Schiff-base calixpyrroles (H4L) that usually act as dinucleating ligands for transition metals. While reactions between H4L and Zn{N(SiMe3)(2)}(2) form the expected dinuclear Zn "Pacman" complexes Zn-2(L), reactions with ZnEt2 result in the tetranuclear Zn alkyl complexes Zn4Et4(THF)(4)(L), in which open, "bowl-shaped" structures are adopted due to the flexibility of the macrocyclic platform: The outcome of hydrolysis reactions of these tetranuclear complexes is found to depend on the macrocyclic Cavity size, with the smaller macrocycle favoring oxo formation in Zn-4(mu(4)-O)Et-2(L) and the larger macrocycle favoring complete hydrolysis to form the hydroxide-bridged cluster Zn-4(mu(2)-OH)(4)(L). This latter complex reacts with carbon dioxide at elevated temperature, reforming the free macrocycle H4L and eliminating ZnCO3.