Synthesis and Bonding in Carbene Complexes of an Unsymmetrical Dilithio Methandiide: A Combined Experimental and Theoretical Study
Synthesis and Bonding in Carbene Complexes of an Unsymmetrical Dilithio Methandiide: A Combined Experimental and Theoretical Study
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DOI：
10.1002/chem.201303115
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发表时间：
2013-12-02
影响因子：
4.3
通讯作者：
Kaupp, Martin
中科院分区：
文献类型：
--
作者：
Gessner, Viktoria H.;Meier, Florian;Kaupp, Martin
本文报道了一种新的不对称双（硫代膦酰）取代二硫代甲二胺的制备及其在锆和钯碳配合物合成中的应用。发现这些配合物表现出明显的屏蔽(CNMR)-C-13位移，其高场位移远高于正常的碳配合物。进行了DFT计算，以确定这些观察的起源，并将这些和相关的碳配合物与经典的Fischer和schrock型配合物进行比较，以区分电子结构。各种方法表明，这些体系最好被描述为高度极化的Schrock型配合物，其中金属-碳键比原型Schrock系统具有更多的静电贡献，甚至作为掩膜甲烷化物。因此，双离子代表了一种极端的Schrock型配体，倾向于离子共振结构M+CR2-，这在教科书中经常被用来解释Schrock配合物的亲核性质。
Herein, we report the preparation of a new unsymmetrical, bis(thiophosphinoyl)-substituted dilithio methandiide and its application for the synthesis of zirconium- and palladium-carbene complexes. These complexes were found to exhibit remarkably shielded (CNMR)-C-13 shifts, which are much more highfield-shifted than those of normal carbene complexes. DFT calculations were performed to determine the origin of these observations and to distinguish the electronic structure of these and related carbene complexes compared with the classical Fischer and Schrock-type complexes. Various methods show that these systems are best described as highly polarized Schrock-type complexes, in which the metal-carbon bond possesses more electrostatic contributions than in the prototype Schrock systems, or even as masked methandiides. As such, geminal dianions represent a kind of extreme Schrock-type ligands favoring the ionic resonance structure M+CR2- as often used in textbooks to explain the nucleophilic nature of Schrock complexes.