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標題: | 高路易斯酸性胺基硼烷化合物:合成與分析 An Endeavor to Enhance Lewis Acidity of Amino Borane |
作者: | Ching-An Chang 張菁安 |
指導教授: | 邱靜雯(Ching-Wen Chiu) |
關鍵字: | 胺基硼烷,二氮雜環,硼陽離子,胺基取代反應,路易斯酸性, amino borane,cyclic diamine,boron cation,amine substitution,Lewis acidity, |
出版年 : | 2020 |
學位: | 碩士 |
摘要: | 二配位和三配位的胺基硼烷化合物中的硼氮雙鍵是穩定化合物的主要因素。然而,也鑒於硼氮之間作用,壓抑硼本身缺電子的本質。儘管氮是屬於電負度較大的原子,和硼同是第二周期的元素,有效的提升軌域和能量的相合相容,導致 -withdrawing的能力相形見絀。常見提升胺基硼烷化合物的路易斯酸性的方法是藉由引入拉電子基團,削弱硼氮之間的π電子作用。我們利用 Bredt’s Rule 的原理,將二氮雜環作為硼的雙牙基,設計一個雙環結構使兩個胺基正好在橋頭的位置,同時加入 N-heterocyclic carbene 來提供整個系統必要的動力學和熱力學穩定。分子透過理論計算證實和B(C6F5)3有相當的 Hydride Ion Affinity。從實驗結果推測三配位硼烷起始物和二胺雜環會抑制分子內第二個胺基取代反應,所以我們轉換合成路徑,利用四配位的NHC 硼烷作為起始物,合成目標二胺基硼陽離子的先驅物。我們也嘗試將二氮雜環做鋰化,藉以增強親核性。實驗結果發現有適當立體障礙的IMe boranes 有相對比較高的反應性;強親核性的鋰化二氮雜環因為溶解度過差而反應性不理想;相較於B-Cl,B-I 鍵太弱,不適合做為起始物。理想的結合是IMe boranes和二氮雜環的組合,但是反應後的產物分析較為複雜。 Amino boranes are known to be reluctant towards base coordination owing to the strong p-donating ability of amino group that overshadows the s-withdrawing effect of nitrogen atom. To maximize the inductive effect of nitrogen, we have designed a diamino-borenium cation, in which the B-N p-interaction is blocked by structural restrain. Theoretical calculations on the isodesmic reaction between [HBEt3]- and a series of boron compounds suggest that the designed diamino borenium cation could possess Lewis acidity comparable to B(C6F5)3. Unfortunately, all efforts in achieving the strained diamino-borenium cation were unsuccessful. Initial attempt in synthesizing the BN2-containing bicyclic compound through reaction of homopiperazine and boron trichloride was failed due to the formation B=N bond that prevents the addition of second amino group. Later, the synthetic routes starting from NHC-coordinated boranes, including NHC-BH3, NHC-BHCl2, NHC-BCl3, and NHC-BHI2, were also examined. While the coordination of bulky IMes ligand hampers the substitution at boron, complicated mixtures were obtained when small IMe ligand was applied. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/19809 |
DOI: | 10.6342/NTU202003458 |
全文授權: | 未授權 |
顯示於系所單位: | 化學系 |
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