Department of Chemistry, University of Fribourg, Chemin du Musee 9, CH-1700 Fribourg, Switzerland.
Inorg Chem. 2011 Sep 5;50(17):8188-96. doi: 10.1021/ic200651h. Epub 2011 Aug 11.
A series of bimetallic N-heterocyclic carbene (NHC) ruthenium(II) complexes were synthesized, which comprise two [RuCl(2)(cymene)(NHC)] units that are interlinked via the NHC nitrogens by alkyl chains of different length. Electrochemical characterization revealed two mutually dependent oxidation processes for the complex with a methylene linker, indicating moderate intramolecular electronic coupling of the two metal centers (class II system). The degree of coupling decreases rapidly upon increasing the number of CH(2) units in the linker and provides essentially decoupled class I species when propylene or butylene linkers are used. Electrochemical analyses combined with structural investigations suggest a through-bond electronic coupling. Replacement of the alkyl linker with a p-phenylene group afforded cyclometalated complexes, which were considerably less stable. The electronic coupling in the methylene-linked complex and the relatively robust NHC-ruthenium bond may provide access to species that are switchable on the molecular scale.
一系列双金属 N-杂环卡宾（NHC）钌（II）配合物被合成，其中包含两个[RuCl2（cymene）（NHC）]单元，通过烷基链在 NHC 氮原子之间连接，链长不同。电化学特性研究表明，具有亚甲基连接体的配合物有两个相互依赖的氧化过程，表明两个金属中心的中等程度的分子内电子偶联（II 类体系）。当使用亚丙基或亚丁基连接体时，连接体中亚甲基单元数量的增加会迅速降低偶联程度，并提供实质上解耦的 I 类物种。电化学分析与结构研究相结合表明，存在通过键的电子偶联。用亚苯基取代烷基连接体得到了环金属化配合物，其稳定性要差得多。亚甲基连接体中的电子偶联和相对稳定的 NHC-钌键可能为在分子尺度上可切换的物种提供了途径。
