The distinguishing feature of α-cationic phosphines is the presence of at least one substituent, normally (hetero)cyclic and positively charged, which is directly attached to the phosphorus atom. As result from this unique substitution pattern, the thus designed ligands depict significantly diminished donor properties if compared with their neutral counterparts. Thus, if in a hypothetical catalytic cycle, the step that determines the rate is facilitated by an increase of the electrophilicity at the metal center; then, the use of α-cationic ancillary phosphines can be highly beneficial. This fact, combined with their easy syntheses and stability, which allows an easy handling, make α-cationic phosphines a useful tool for the synthetic practitioner. Our research on the topic demonstrates that generally a remarkable ligand acceleration effect is observed when α-cationic phosphines are employed in Au(I)- and Pt(II)-promoted cycloisomerizations; moreover, in some cases even otherwise not operative transformations can be promoted. This Account describes how we entered into the topic, our efforts, and those of others to understand the coordination behavior of α-cationic phosphines and further develop their range of applications in catalysis; but it also identifies the drawbacks associated with their use, which limit their range of application.

1 Introduction

2 Polycationic Phosphines: Stronger Acceptors than Phosphites

3 Inconveniences Derived from the Use of (Poly)cationic phosphines

4 A Second Generation of Cationic Ligands: α-Pyridiniophosphines

5 Chiral α-Cationic Phosphines

6 α-Radical Phosphines and (Poly)cationic Phosphine Oxides

7 Conclusions and Outlook

α-阳离子膦的显着特征是存在至少一个取代基，通常为（杂）环且带正电荷，其直接连接到磷原子上。由于这种独特的取代模式，因此设计的配体与其中性对应物相比表现出显着减弱的供体特性。因此，如果在一个假设的催化循环中，决定速率的步骤是通过增加金属中心的亲电性来促进的；那么，α-阳离子辅助膦的使用是非常有益的。这一事实，再加上它们易于合成和稳定性，易于处理，使 α-阳离子膦成为合成从业者的有用工具。我们对该主题的研究表明，当在 Au(I) 和 Pt(II) 促进的环异构化中使用 α-阳离子膦时，通常会观察到显着的配体加速效果；此外，在某些情况下，甚至可以促进无效的转换。本报告描述了我们如何进入该主题、我们的努力以及其他人为了解 α-阳离子膦的配位行为并进一步开发其在催化中的应用范围而做出的努力；但它也指出了与它们的使用相关的缺点，这限制了它们的应用范围。以及其他人了解α-阳离子膦的配位行为并进一步发展它们在催化中的应用范围；但它也指出了与它们的使用相关的缺点，这限制了它们的应用范围。以及其他人了解α-阳离子膦的配位行为并进一步发展它们在催化中的应用范围；但它也指出了与它们的使用相关的缺点，这限制了它们的应用范围。

1 简介

2 聚阳离子膦：比亚磷酸盐更强的受体

3 使用（聚）阳离子膦带来的不便

4 第二代阳离子配体：α-吡啶膦

5 手性α-阳离子膦

6 α-自由基膦和（聚）阳离子氧化膦

7 结论与展望