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  • 學位論文

萘啶羧酸衍生物配位基金屬錯合物之合成與催化應用

Synthesis and Catalytic Application of Metal Complexes with Naphthyridine Carboxylic Acid Derivatives Ligands

指導教授 : 劉緒宗

摘要


本篇研究合成了三種不同的萘啶羧酸衍生物配位基,1,8-Naphthyridine-2-carboxylic acid (L1)、1,8-Naphthyridine-2-carboxamide (L2)、N-(pyridin-2-ylmethyl)-1,8-naphthyridine-2-carboxamide (L3),將其分別與銠或銥金屬先驅物進行配位反應,可以製備出相對應的金屬錯合物[Rh(COD)(L1)] (2)、[Ir(COD)(L1)] (3)、[Ir(COD)(L2)] (4)、[Ir(COD)(L3)] (5)、[Ir(COD)(L1)HCl] (8)、[Ir(COD)(L1)Cl2] (9),上述錯合物結構皆透過核磁共振光譜、紅外線光譜、質譜、X-射線單晶繞射等項完成鑑定。 為探討不同羧酸衍生物的配位基效應,將錯合物應用於苯胺與苯甲醇的N-烷基化反應,以碳酸銫作為鹼,於無溶劑且氮氣環境下加熱120 °C進行,比較錯合物3、4、5之催化活性。結果顯示這類帶有醯胺官能基配位的錯合物4、5,於反應中皆展現了優良的催化活性;此外,與羧酸根錯合物3相較之下有著明顯差異,這是歸因於醯胺陰離子比羧酸根更具良好的電子貢獻能力。另再改於甲苯溶劑系統下進行相同反應,則由於錯合物5其配位基本身帶有的吡啶,可於反應過程中與金屬中心配位,提供額外的穩定性,故其反應性會優於錯合物4。 另外,在實驗中發現,錯合物3、4能夠透過催化量銥(0)之幫助,於氫氣一大氣壓,室溫下被還原為銥(0)粒子,而錯合物5則由於在三牙配位基的穩定下,無法進行相同的還原反應。為了測試銥金屬先驅物及錯合物3、4在硝基苯非勻相氫化反應的催化活性,以催化量[Ir(COD)Cl]2作為添加劑,一大氣壓氫氣作為還原劑,在室溫中甲醇溶劑下進行反應,結果顯示在配位基的幫助下,可以避免金屬粒子相互聚集,因此比[Ir(COD)Cl]2、[Ir(COD)(OMe)]2還原生成的銥(0)更具反應活性。 最後,為凸顯非勻相催化的應用價值,透過中孔洞材料SBA-15,或是矽膠作為載體,於上述非勻相氫化反應條件下可分別製備出Ir/SBA-15、Ir/SiO2,它們將使催化活性得到進一步提升,在五次回收催化實驗中均展現了良好的重複利用性,並同時具有反應條件溫和、低催化量、反應時間短等優點。

並列摘要


Three different naphthyridine carboxylic acid derivative ligands, 1,8-Naphthyridine-2-carboxylic acid (L1), 1,8-Naphthyridine-2-carboxamide (L2), and N-(pyridin-2-ylmethyl)-1,8-naphthyridine-2-carboxamide (L3), are synthesized. Complexation of [Rh(COD)Cl]2, [Ir(COD)(OMe)]2, and [Ir(COD)Cl]2, with L1, L2, and L3, provided the corresponding complexes [Rh(COD)(L1)] (2), [Ir(COD)(L1)] (3), [Ir(COD)(L2)] (4), [Ir(COD)(L3)] (5), [Ir(COD)(L1)HCl] (8), and [Ir(COD)(L1)Cl2] (9), respectively. These complexes have been characterized by spectroscopic methods and further confirmed by X-ray crystallography. In order to investigate the ligand effect, these complexes are applied to the catalytic N-alkylation of aniline with benzyl alcohol using cesium carbonate as the base under nitrogen atmosphere at 120 °C in the absence of solvent. It turns out that complexes 4 and 5, with an amide moiety, show a better catalytic activity for this N-alkylation. Its high catalytic activity is attributed to stronger electron donation of amido moiety. However, the same reaction was performed in toluene, giving different outcomes. Complex 5 displays a higher catalytic activity than that of 4. The observation implies that pyridin-2-ylmethyl group on the ligand of complex 5 can coordinate to the metal center during the reaction, i.e. the pyridine nitrogen acts as a labile donor. In addition, we find that complexes 3 and 4 can be reduced to Ir(0) particles with the help of a catalytic amount of Ir(0) under the atmospheric pressure of hydrogen at room temperature. However, complex 5 fails to undergo this kind of reduction, it presumably attributed to the stabilization of the tridentate ligand, preventing the reduction. For comparison of catalytic activity among iridium precursors, complex 3 and complex 4, we applied these complexes for catalytic hydrogenation of nitrobenzene using [Ir(COD)Cl]2 as an additive in methanol under atmospheric pressure of hydrogen at room temperature. The results show that complex 3, and complex 4 is more reactive than [Ir(COD)Cl]2 and [Ir(COD)(OMe)]2. The difference of the reaction is due to the coordination of ligands on the surface of Ir(0) particles to avoid the aggregation. We move to a further step to improve the recycle use of the heterogeneous catalyst by using mesoporous material SBA-15 or silica gel as the support. Under the same hydrogenation conditions mentioned above, we successfully prepared Ir/SBA-15 and Ir/SiO2. These catalysts demonstrate excellent reusability after a five-time runs. This procedure have advantages of mild reaction conditions, low catalyst loading, short reaction time, and convenient work up.

參考文獻


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