Krossing Ingo, Raabe Ines
University of Karlsruhe, Engesserstrasse Geb. 30.45, 76128 Karlsruhe, Germany.
Angew Chem Int Ed Engl. 2004 Apr 13;43(16):2066-90. doi: 10.1002/anie.200300620.
Is there anything resembling a truly noncoordinating anion? Would it not be great to be able to prepare any crazy, beautiful, or simply useful cationic species that one has in mind, or has detected by mass spectroscopy? In condensed phases the target cation has to be partnered with a suitable counteranion. This is the moment when difficulties arise and many wonderful ideas end in the sink owing to coordination or decomposition of the anion. However, maybe these counteranion problems can be overcome by one of the new weakly coordinating anions (WCAs). Herein is an overview on the available candidates in the quest for the least coordinating anion and a summary of new applications, available starting materials, and general strategies to introduce a WCA into a system. Some of the unusual properties of WCA salts such as high solubility in low dielectric media, pseudo gas-phase conditions in condensed phases, and the stabilization of weakly bound and low-charged complexes are rationalized on thermodynamic grounds. Limits of the WCAs, that is, anion coordination and decomposition, are shown and a quantum chemical analysis of all types of WCAs is presented which allows the choice of a particular WCA to be based on quantitative data from a wide range of different anions.
是否存在类似真正不发生配位作用的阴离子呢？能够制备出任何人们心中所想或通过质谱检测到的疯狂、美妙或仅仅有用的阳离子物种，这难道不是很棒吗？在凝聚相中，目标阳离子必须与合适的抗衡阴离子配对。就在此时困难出现了，许多绝妙的想法由于阴离子的配位或分解而付诸东流。然而，或许这些抗衡阴离子问题可以通过一种新型的弱配位阴离子（WCA）来克服。本文综述了在寻找最弱配位阴离子过程中可用的候选物，总结了新的应用、可用的起始原料以及将WCA引入体系的一般策略。基于热力学原理，对WCA盐的一些不寻常性质进行了合理化解释，如在低介电介质中的高溶解度、凝聚相中的准气相条件以及弱键合和低电荷配合物的稳定化。展示了WCA的局限性，即阴离子配位和分解，并对所有类型的WCA进行了量子化学分析，这使得可以根据来自广泛不同阴离子的定量数据来选择特定的WCA。
