Taakili Rachid, Barthes Cécile, Lepetit Christine, Duhayon Carine, Valyaev Dmitry A, Canac Yves
LCC-CNRS, Université de Toulouse, CNRS, 205 route de Narbonne, 31077 Cedex 4 Toulouse, France.
Inorg Chem. 2021 Aug 16;60(16):12116-12128. doi: 10.1021/acs.inorgchem.1c01316. Epub 2021 Aug 2.
The reaction of readily available imidazolium-phosphonium salt MesIm(CH)PPh with PdCl in the presence of an excess of CsCO afforded selectively in one step the cationic Pd(II) complex (,,)Pd(NCMe) exhibiting an LX-type NHC-ylide-aryl ,,-pincer ligand via formal triple C-H bond activation. The replacement of labile MeCN in the latter by CNBu and CO fragments allowed to estimate the overall electronic properties of this phosphonium ylide core pincer scaffold incorporating three different carbon-based donor ends by IR spectroscopy, cyclic voltammetry, and molecular orbital analysis, revealing its significantly higher electron-rich character compared to the structurally close NHC core pincer system with two phosphonium ylide extremities. The pincer complex (,,)Pd(CO) represents a rare example of Pd(II) carbonyl species stable at room temperature and characterized by X-ray diffraction analysis. The treatment of isostructural cationic complexes (,,)Pd(NCMe) and (,,)Pd(CO) with (allyl)MgBr and BuLi led to the formation of zwitterionic phosphonium organopalladates [(,,)PdBr] and [(,,)Pd(COBu)], respectively.
在过量碳酸铯存在下，易得的咪唑鎓 - 鏻盐MesIm(CH)PPh与氯化钯反应，通过形式上的三重C - H键活化，一步选择性地得到阳离子钯(II)配合物(,,)Pd(NCMe)，其具有LX型NHC - 叶立德 - 芳基,, - 钳形配体。通过用CNBu和CO片段取代后者中不稳定的乙腈，利用红外光谱、循环伏安法和分子轨道分析，可以评估这种包含三个不同碳基供体端的鏻叶立德核心钳形支架的整体电子性质，结果表明与具有两个鏻叶立德末端的结构相近的NHC核心钳形体系相比，其富电子特性明显更高。钳形配合物(,,)Pd(CO)是室温下稳定的钯(II)羰基物种的罕见例子，并通过X射线衍射分析进行了表征。用(烯丙基)溴化镁和丁基锂处理同构阳离子配合物(,,)Pd(NCMe)和(,,)Pd(CO)，分别导致形成两性离子鏻有机钯酸盐[(,,)PdBr]和[(,,)Pd(COBu)]。
