Merz Lukas S, Wadepohl Hubert, Clot Eric, Gade Lutz H
Anorganisch Chemisches Institut , Universität Heidelberg , Im Neuenheimer Feld 270 , 69120 Heidelberg , Germany . Email:
Institut Charles Gerhardt Montpellier , UMR 5253 CNRS-UM-ENSCM , Université de Montpellier , Place Eugène Bataillon, Bât 15, cc1501 , 34095 Montpellier Cedex 5 , France . Email:
Chem Sci. 2018 May 16;9(23):5223-5232. doi: 10.1039/c8sc01025k. eCollection 2018 Jun 21.
The mechanism of the reductive homocoupling of pyridine derivatives mediated by the Zr synthon [(PNP)Zr(η-toluene)Cl] () has been investigated. Selective transformation into three different types of product complexes has been observed, depending on the N-heterocyclic substrate employed: the bipyridyl complexes (R = Me, Et, Bu, Bn, Ph, CHCHPh), which are the homocoupling products, the η-((4-dimethylamino)pyridyl) complex as well as the bis(isoquinolinyl) complex . By deuterium labelling experiments the participation of the ligand backbone in the pyridine coupling reaction potential cyclometallation steps was ruled out. Based on DFT modelling of the possible reaction sequences a reaction mechanism for the coupling sequence could be identified. The latter is initiated by a reductive C-C coupling rather than based on an initial C-H activation of the pyridine substrate.
已对由锆合成子[(PNP)Zr(η-甲苯)Cl]（）介导的吡啶衍生物还原均偶联反应的机理进行了研究。根据所使用的N-杂环底物，观察到选择性转化为三种不同类型的产物配合物：作为均偶联产物的联吡啶配合物（R = 甲基、乙基、丁基、苄基、苯基、苯乙烯基苯基）、η-((4-二甲基氨基)吡啶基)配合物以及双(异喹啉基)配合物。通过氘标记实验排除了配体主链参与吡啶偶联反应（潜在的环金属化步骤）的可能性。基于对可能反应序列的密度泛函理论建模，可确定偶联序列的反应机理。后者由还原的C-C偶联引发，而非基于吡啶底物的初始C-H活化。
