雙取代磷陽離子

Abstract

在這個研究中，我們嘗試合成多種二配位磷陽離子化合物。由於高氧化態且配位數較低的磷陽離子極不穩定且極具反應性，合成這些化合物十分具有挑戰性。我們受到Bertrand團隊的研究啟發，他們通過對cAAC穩定的氨基磷烯前趨物進行單電子氧化，成功地得到二配位的磷自由基陽離子。在此基礎上，我們進一步探索了二配位的磷二正陽離子。我們希望透過對cAAC-氨基磷烯進行兩當量電子的氧化來生成雙取代的磷雙陽離子。然而，生成的cAAC-雙取代磷雙陽離子反應性過高並產生了不在預期中的氫化反應，形成了cAAC配基的氮基氫化磷陽離子[cAAC-P(H)R]+。除此之外，我們預期將π-酸性的cAAC配基替換為π-鹼性的CDC配基，這個配基有助於提高二配位磷自由基陽離子的反應性。我們預期能通過對CDC配體的雙取代磷雙陽離子進行單電子還原獲得自由基陽離子。我們測得經過還原反應的氨基取代磷雙陽離子的電子自旋共振光譜，但單晶結構仍未被證明；另外，氯取代的磷雙陽離子在溶液中會發生雙磷雙陽離子的雙聚反應，低溫下EPR訊號較強，但我們目前並未測得明顯的雙自由基訊號。

In this project, we have explored the synthesis of several di-coordinated phosphorus cationic complexes. As phosphorus in high oxidation state with low coordination number is extremely unstable and highly reactive, the synthesis of these complexes was relatively challenging. Inspired by the work of Bertrand’s group, where a di-coordinated phosphinyl radical cation was obtained by one-electron oxidation of the cAAC-stabilized amino-phosphinidene precursor, two types of di-coordinated phosphorus cations were explored. We hypothesized that we might be able to generate di-substituted phosphorus dication from two-electron oxidation of the cAAC-phosphinidene adduct. However, the generated cAAC-coordinate di-substituted phosphorus dication is too reactive and undergoes unexpected hydride abstraction reaction from the solvent to yield the cAAC-coordinate parent phosphenium cation [cAAC-P(H)R]+. In addition, replacing the -acidic cAAC ligand with a -donating CDC is expected to raise the reactivity of the di-coordinated phosphinyl radical cation. The anticipated radical species could potentially be obtained from one-electron reduction of the CDC-coordinated di-substituted phosphorus dication. We have already got the EPR spectrum of the reduced product of the amino-substituted dication but the structure is still under investigation. Otherwise, the chloride-functionalized analogue dimerizes to give diphosphorus dication.