Pd2(dba)3 的难以捉摸的结构。通过同位素标记、NMR 光谱和 X 射线衍射分析进行检查：Pd2(dba-Z)3 配合物的合成和表征,Journal of the American Chemical Society

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Pd2(dba)3 的难以捉摸的结构。通过同位素标记、NMR 光谱和 X 射线衍射分析进行检查：Pd2(dba-Z)3 配合物的合成和表征
Journal of the American Chemical Society ( IF 15.6 ) Pub Date : 2013-05-23 , DOI: 10.1021/ja403259c
Anant R. Kapdi , Adrian C. Whitwood , David C. Williamson , Jason M. Lynam , Michael J. Burns , Thomas J. Williams , Alan J. Reay , Jordan Holmes , Ian J. S. Fairlamb

Pd(0)2(dba)3（dba = E,E-二亚苄基丙酮）是 Pd 介导的转化中使用最广泛的 Pd(0) 源。Pd(0)2(dba-Z)3（Z = dba 芳基取代基）配合物在一系列不拘一格的交叉偶联反应中表现出显着且差异化的催化性能。从 1970 年代的早期研究到现在，这些类型的复合物的精确结构一直令人困惑。在这项研究中，已经确定了 Pd(0)2(dba)3 和 Pd(0)2(dba-Z)3 的溶液和固态结构。同位素标记 ((2)H 和 (13)C) 允许在高场 (700 MHz) 下确定 Pd(0)2(dba)3 的自由交换主要和次要异构体的溶液结构。DFT 计算支持实验确定的主要和次要异构结构，这表明 Pd(0)2(dba)3 的主要异构体具有仅在 s-cis,s-trans 构象中发现的桥连 dba 配体。对于次要异构体，发现 dba 配体之一仅在 s-trans,s-trans 构象中。Pd(0)2(dba)3·CHCl3（高质量数据）的单晶 X 射线衍射分析表明，所有三个 dba 配体都位于两个位置。Pd(0)2(dba-Z)3 的 NMR 光谱分析表明，芳基取代基对 Pd-烯烃交换速率和溶液中配合物的整体稳定性具有深远的影响。含有芳基取代基、4-CF3、4-F、4-t-Bu、4-己氧基、4-OMe 的配合物在 298 K 下表现出良好的 (1)H NMR 谱，而含有 3,5-OMe 的配合物和 3,4,5-OMe 表现出广泛的光谱。三种 Pd(0)2(dba-Z)3 配合物 (4-F, 4-OMe, 3,

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The Elusive Structure of Pd2(dba)3. Examination by Isotopic Labeling, NMR Spectroscopy, and X-ray Diffraction Analysis: Synthesis and Characterization of Pd2(dba-Z)3Complexes

Pd(0)2(dba)3 (dba = E,E-dibenzylidene acetone) is the most widely used Pd(0) source in Pd-mediated transformations. Pd(0)2(dba-Z)3 (Z = dba aryl substituents) complexes exhibit remarkable and differential catalytic performance in an eclectic array of cross-coupling reactions. The precise structure of these types of complexes has been confounding, since early studies in 1970s to the present day. In this study the solution and solid-state structures of Pd(0)2(dba)3 and Pd(0)2(dba-Z)3 have been determined. Isotopic labeling ((2)H and (13)C) has allowed the solution structures of the freely exchanging major and minor isomers of Pd(0)2(dba)3 to be determined at high field (700 MHz). DFT calculations support the experimentally determined major and minor isomeric structures, which show that the major isomer of Pd(0)2(dba)3 possesses bridging dba ligands found exclusively in a s-cis,s-trans conformation. For the minor isomer one of the dba ligands is found exclusively in a s-trans,s-trans conformation. Single crystal X-ray diffraction analysis of Pd(0)2(dba)3·CHCl3 (high-quality data) shows that all three dba ligands are found over two positions. NMR spectroscopic analysis of Pd(0)2(dba-Z)3 reveals that the aryl substituent has a profound effect on the rate of Pd-olefin exchange and the global stability of the complexes in solution. Complexes containing the aryl substituents, 4-CF3, 4-F, 4-t-Bu, 4-hexoxy, 4-OMe, exhibit well-resolved (1)H NMR spectra at 298 K, whereas those containing 3,5-OMe and 3,4,5-OMe exhibit broad spectra. The solid-state structures of three Pd(0)2(dba-Z)3 complexes (4-F, 4-OMe, 3,5-OMe) have been determined by single crystal X-ray diffraction methods, which have been compared with Goodson's X-ray structure of Pd(0)2(dba-4-OH)3.

更新日期：2013-05-23

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