E.N.S.C.P., Chimie-ParisTech, UMR 7223, Laboratoire Charles Friedel, 11 rue P. et M. Curie, 75231 Paris Cedex 05, France.
Dalton Trans. 2010 Nov 28;39(44):10608-16. doi: 10.1039/c0dt00399a. Epub 2010 Sep 29.
Enantiopure undecagold clusters protected by chiral atropisomeric diphosphine ligands (P^P) have been synthesized by the stoichiometric reduction of the corresponding (P^P)(AuCl)(2) complexes with NaBH(4). The molecular mono-disperse [Au(11)(P^P)(4)Cl(2)]Cl species have been thoroughly characterized using an array of analytical techniques. (31)P NMR experiments suggested the presence of a slow intramolecular ligand exchange process. Circular dichroism measurements showed that enantiomeric clusters display mirror-image chiroptical activity. Such undecagold clusters containing two chloride ligands bound to the peripheral Au(I) atoms were expected to display a carbophilic Lewis acidity similar to the well-documented molecular Au(I) complex catalysts. Chloride abstraction, performed to generate active Au(+) sites, induced the Au(11) cluster evolution to larger gold clusters and nanoparticles, together with Au(I) complexes, which, in fact, perform the catalysis. This result was corroborated by running an asymmetric tandem hydroarylation-carbocyclization reaction, for which the enantiomeric excesses obtained with Au(11) clusters are similar to those reported using Au(I) complexes.
手性非对映纯十一金簇由手性-atropisomeric 双膦配体（P^P）保护，通过相应的（P^P）（AuCl）（2）配合物与 NaBH（4）的化学计量还原合成。使用一系列分析技术彻底表征了分子单分散的[Au（11）（P^P）（4）Cl（2）]Cl 物种。（31）P NMR 实验表明存在缓慢的分子内配体交换过程。圆二色性测量表明，对映体簇显示镜像手性光学活性。预期含有两个结合在外围 Au（I）原子上的氯离子的十一金簇将显示类似于文献报道的分子 Au（I）配合物催化剂的亲碳路易斯酸度。为了生成活性 Au（+）位点而进行的氯化物消除，导致 Au（11）簇演化为更大的金簇和纳米颗粒，以及 Au（I）配合物，实际上，它们进行了催化。通过运行不对称串联氢芳基化-碳环化反应证实了这一结果，用 Au（11）簇获得的对映体过量与使用 Au（I）配合物报告的对映体过量相似。
