Alcarazo Manuel
Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 41470 Mülheim an der Ruhr (Germany).
Chemistry. 2014 Jun 23;20(26):7868-77. doi: 10.1002/chem.201402375. Epub 2014 May 30.
In coordination chemistry, typical ancillary ligands are anionic or neutral species. Cationic ones are exceptions and, when used, the positively charged groups are normally attached to the periphery and not close to the donating atom. However, this concept article highlights a series of recent experimental, as well as theoretical results, suggesting that the utility in catalysis of cationic phosphines with no spacer between the phosphorus atom and the positively charged group(s) has been largely overlooked. In fact, a growing number of studies indicate that, because of their specific architecture, these cationic ligands depict excellent π-acceptor character that can exceed that of phosphites or polyfluorinated phosphines. This property has been used to increase the Lewis acidity of the metals they coordinate. Specifically, new extreme π-acid catalysts, mainly based on Pt(II) and Au(I) , have been recently prepared and their superior performance demonstrated along several mechanistically distinct transformations. In this concept article the current state of the art is critically assessed and possible future directions of the topic discussed.
在配位化学中，典型的辅助配体是阴离子或中性物种。阳离子配体则是例外，当使用阳离子配体时，带正电荷的基团通常连接在周边，而不靠近供体原子。然而，这篇概念文章强调了一系列近期的实验以及理论结果，表明磷原子与带正电荷基团之间没有间隔基的阳离子膦在催化中的应用在很大程度上被忽视了。事实上，越来越多的研究表明，由于其特定的结构，这些阳离子配体表现出优异的π受体特性，其π受体特性可能超过亚磷酸酯或多氟膦。这一特性已被用于提高它们所配位金属的路易斯酸性。具体而言，最近制备了主要基于Pt(II)和Au(I)的新型极端π酸催化剂，并在几种机理不同的转化反应中证明了它们的优异性能。在这篇概念文章中，对当前的技术水平进行了批判性评估，并讨论了该主题未来可能的发展方向。
