雙功能氮異環碳烯配基銠金屬錯合物

Rhodium Complex With Bifunctional N-Heterocyclic Carbene Lignad

汪展弘(Chan-Hung Wang)

指導教授 ： 劉緒宗

國立臺灣大學/理學院/化學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201904312

摘要

氮異環碳烯本身穩定性高且容易進行結構修飾，使其兩旁取代基種類相當廣泛，因此其電子性質與立體性質皆有高度多樣性。氮異環碳烯金屬錯合物具有高催化活性，因此被廣泛運用於催化反應。在氫化反應中，氮異環碳烯以很強的σ-donating能力，增加錯合物金屬中心之電子密度，進而增加 Hydricity of metal hydride與錯合物金屬之d軌域電子Back donation 能力，有利於活化氫氫鍵，因此能有效提升氫化反應之反應活性。
喹啉氫化反應是工業中重要的製程，其氫化產物四氫喹啉的衍生物被廣泛運用於藥物化學。然而，在大部分的反應都是在高壓氫氣下進行。在本篇論文中，合成並鑑定雙功能氮異環碳烯銠金屬錯合物10，其可在溫和的一大氣壓下將喹啉氫化。為瞭解錯合物10的氨基於喹啉氫化反應中的角色，合成錯合物11, 12, 13，並且發現錯合物10的反應活性遠高於其他錯合物，且反應性高至低順序為10>11>12>13。根據此結果推測取代基之電子效應改變萘啶上未參與配位之含氮雜環的鹼性，進而影響錯合物的氫化活性。其中錯合物10的含氮雜環鹼性最強，最有能力接收氫氣斷裂後產生的質子，因此展現最佳的反應活性。在研究過程中發現，水在氫氣活化步驟中不可或缺，推測水大幅降低氫氣斷裂所需之活化能。

關鍵字

雙功能配基 ； 氫化 ； 銠金屬錯合物

並列摘要

N-Heterocyclic carbenes have high stability and structural diversity including electronic and steric due to its easy structure modifying. N-Heterocyclic carbene complexes are widely used in catalytic reaction because of its high catalytic reactivity. In the catalytic hydrogenation, NHC-ligand increases the hydricity of metal hydride and the back donation ability from d orbitals of metal to σ* orbitals of H-H bond promoting hydrogen activation, which results from the powerful σ-donating ability of NHC-ligand.
1,2,3,4-tetrahydroquinoline and its derivatives are widely used in pharmaceutical chemistry, it can be produced by quinoline hydrogenation. However, most of the reaction conditions are under high H2 pressure. Rhodium complex 10, Rh(L)Cp*Cl2, (L) = 3-(7-amino-1,8-naphthyridin-2-yl)-1-mesityl-1H-imidazol-3-ium-2-ide, was synthesized and characterized. Complex 10 is designed as a bifunctional complex and it is applied to quinoline hydrogenation under mild atmospheric H2 with AgNO3 as additive. To understand the role of amino substituent on complex 10 in this catalytic system, complex 11, 12, 13 were synthesized. In the following experiment, complex 10 demonstrated significant higher reactivity toward other complex and the reactivity order from highest to lowest is 10>11>12>13. Substituent electronic effect affecting the basicity of non-participating coordination part of ligand was deduced. Complex 10 possesses the highest basicity of non-participating coordination part of ligand, which has the strongest ability to accept proton from hydrogen heterolytic cleavage. Also, the activation energy of dihydrogen heterolytic cleavage is dramatically lower by water which is necessary in the hydrogen gas activation step.

並列關鍵字

Bifunctional Ligand ； Hydrogenation ； Rhodium Complex

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