Caramori Giovanni F, Garcia Leone C, Andrada Diego M, Frenking Gernot
Departamento de Química, Universidade Federal de Santa Catarina, CP 476, Florianópolis, SC 88040-900, Brazil.
Dalton Trans. 2014 Oct 21;43(39):14710-9. doi: 10.1039/c4dt01473a.
The present work seeks to characterize, in the light of electronic structure calculations, an unusual metal-[(η(1)-NHC)2:(η(6)-arene)] bonding situation in a set of ruthenium(ii) complexes containing the ortho-xylylene-linked-bis(NHC)cyclophane ligand (NHC-cyclophane) (), which binds to the ruthenium center through two carbene carbons and one of the arene rings. The nature of ruthenium(ii)-[(η(1)-NHC)2:(η(6)-arene)] bonding was investigated in the light of EDA-NOCV, NBO and QTAIM analyses by adopting as a model compound. The interplay between the ortho-cyclophane scaffold with different families of five-membered carbenes, such as imidazole, , triazole-based NHCs (Enders' carbenes), , and P-heterocyclic carbenes (PHCs), , was investigated. The metal-[(η(1)-NHC)2:(η(6)-arene)] bonding situation was also extended to heavier analogues, such as N-heterocyclic silylenes (NHSi) and N-heterocyclic germylenes (NHGe), in order to address how the basicity of NHC, NHSi and NHGe is affected by the cyclophane framework. The results reveal that ruthenium(ii)-[(η(1)-NHC)2:(η(6)-arene)] is more covalently than electrostatically bonded and that the degree of covalence is larger in PHCs than in NHCs or Enders' carbenes. It is also revealed that the covalent character in the ruthenium(ii)-[(η(1)-NHGe)2:(η(6)-arene)] and ruthenium(ii)-[(η(1)-NHSi)2:(η(6)-arene)] bonds is larger than in ruthenium(ii)-[(η(1)-NHC)2:(η(6)-arene)].
本工作旨在根据电子结构计算，对一组含有邻二甲苯连接的双（NHC）环番配体（NHC-环番）（）的钌（II）配合物中异常的金属-[(η(1)-NHC)2:(η(6)-芳烃)]键合情况进行表征，该配体通过两个卡宾碳和一个芳烃环与钌中心结合。通过采用作为模型化合物，根据EDA-NOCV、NBO和QTAIM分析研究了钌（II）-[(η(1)-NHC)2:(η(6)-芳烃)]键合的性质。研究了邻环番支架与不同家族的五元卡宾（如咪唑、、基于三唑的NHC（恩德斯卡宾）、和P-杂环卡宾（PHC）、）之间的相互作用。金属-[(η(1)-NHC)2:(η(6)-芳烃)]键合情况也扩展到了较重的类似物，如N-杂环硅烯（NHSi）和N-杂环锗烯（NHGe），以探讨NHC、NHSi和NHGe的碱性如何受环番框架的影响。结果表明，钌（II）-[(η(1)-NHC)2:(η(6)-芳烃)]的键合更具共价性而非静电性，且PHCs中的共价程度大于NHCs或恩德斯卡宾中的共价程度。还表明，钌（II）-[(η(1)-NHGe)2:(η(6)-芳烃)]和钌（II）-[(η(1)-NHSi)2:(η(6)-芳烃)]键中的共价特征大于钌（II）-[(η(1)-NHC)2:(η(6)-芳烃)]中的共价特征。
