具Non-Innocent配基之硼路易士酸

Abstract

具有non-innocent配基的過渡金屬錯合物在化學鍵的活化與催化反應中有許多應用的例子，近年來也有許多將主族元素引入non-innocent配基體系的文獻報導。然而，由三配位有機硼化物和non-innocent配基衍生的路易士酸卻很少被研究。我們認為或許可以結合天生缺電子的硼原子與non-innocent配基，藉由硼原子－配基協同作用來進行化學鍵的活化，並將此反應應用於化學合成上。因此，本研究工作闡述了由non-innocent配基與碳烯穩定的硼陽離子的合成，以及硼陽離子與硼烷氨、苯甲醛和還原劑之間的反應性測試。其中，我們發現含氮雜環碳烯穩定的硼陽離子與硼烷氨的反應產生了氫化硼陽離子以及環硼氮烷。此外，我們還觀察到含氮雜環碳烯穩定的硼陽離子會與苯甲醛進行1,2-碳硼化反應，形成含氮雜環碳烯穩定的惡唑硼烷陽離子。最後，在對含氮雜環碳烯及環烷基氨基碳烯穩定的硼陽離子進行還原後，相關的EPR訊號也被偵測到，不過自由基產物的結構仍在鑑定當中。

Non-innocent ligand supported transition metal complexes have found numerous applications in bond activation and catalysis. In recent years, the incorporation of main-group element into the non-innocent ligand system has also emerged. However, Lewis acids derived from the combination of tri-coordinate organoboron and non-innocent ligand were much less explored. As the combination of non-innocent ligand with highly electron deficient boron atom may be beneficial for synthetic application through heterolytic boron-ligand cooperative bond activation. Accordingly, synthetic plans of non-innocent ligand and carbenes supported boron cations are reported in this work. Reactivities of borenium with ammonia-borane, benzaldehyde, and reductant are also examined. The reaction of IMe4-borenium with ammonia-borane leads to the generation of hydrido-boronium and borazine. Additionally, we observed the 1,2-carboboration of benzaldehyde with IMe4-borenium, resulting in the formation of an IMe4-coordinated oxazaborolidinium. Furthermore, we detected EPR signals upon treatment of NHC- and cAAC-boreniums with reductants. The structures of the resulting radical species are still under investigation.