Revealing the diastereomeric nature of pincer terdentate nitrogen ligands 2,6-bis(arylaminomethyl)pyridine through coordination to palladium

Revealing the diastereomeric nature of pincer terdentate nitrogen ligands 2,6-bis(arylaminomethyl)pyridine through coordination to palladium
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通过与钯的配位揭示钳三齿氮配体 2,6-双（芳基氨基甲基）吡啶的非对映体性质

DOI：
10.1039/b201319c
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发表时间：
2002
期刊：
Journal of The Chemical Society-dalton Transactions
影响因子：
--
通讯作者：
E. Gutiérrez‐Puebla
E. Gutiérrez‐Puebla
中科院分区：
--
文献类型：
--
作者：
A. Arnaiz;J. Cuevas;G. García;Arancha Carbayo;J. A. Casares;E. Gutiérrez‐Puebla

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合成了含钳形三齿配体L [L = 2，6-（ArNHCH_2）_2C_5 H_3 N（Ar = 4-MeC_6 H_41 a和2a，4-MeOC_6 H_41 b和2b）; L = 2，6-（4-MeC_6 H_4 NMeCH_2）_2C_5 H_3 N（1c和2c）]的钯配合物[PdLCl]_X（X = Cl_1，BF_（42））。钳形配体的两个胺臂的手性性质解释了异构体的混合物。所有的复合物都表现出转化的动力学行为 非对映异构体之间。通过对1H光谱中-CH 2-信号的完全DNMR线形分析，发现2a的Δ G 273为68.9 kJ mol − 1，2c的ΔG 273为65.8 kJ mol−1。顺-反转化需要将其中一个配位胺臂的锥形氮反转。已经提出了两种推定的途径来进行这种转化：a）胺氮原子之一的解离，随后氮原子的转化和氮-钯键的重新形成，以及B）N-H键之一的去质子化，导致酰胺基中间体，其可以在另一侧再质子化。这两种机制的实验证据。1a的结构特征 本文介绍
Palladium complexes of formula [PdLCl]X (X = Cl 1, BF42) containing the pincer terdentate ligands L [L = 2,6-(ArNHCH2)2C5H3N (Ar = 4-MeC6H41a and 2a, 4-MeOC6H41b and 2b); L = 2,6-(4-MeC6H4NMeCH2)2C5H3N 1c and 2c] have been synthesised as cis–trans diastereomeric mixtures. The chiral nature of both amine arms of the pincer ligands accounts for the mixtures of isomers. All the complexes show dynamic behavior assigned to conversion between diastereomers. A ΔG‡273 of 68.9 kJ mol−1 for 2a and a ΔG‡273 of 65.8 kJ mol−1 for 2c were found through complete DNMR line-shape analysis of the –CH2– signals in the 1H spectra. The cis–trans conversion requires the inversion of the pyramidal nitrogen of one of the coordinated amine arms. Two putative pathways have been proposed for such inversion: a) dissociation of one of the amine nitrogen atoms followed by inversion of the nitrogen atom and reformation of the nitrogen–palladium bond and b) deprotonation of one of the N–H bond leading to an amido intermediate which can reprotonate on the other side. Experimental evidence is given for both mechanisms. The structural characterization of 1a is described.