陰離子型醯胺基氮異環碳烯銅金屬錯合物與蔥啶配基之雙金屬錯合物其合成與催化應用

Anionic Amido-Tethered N-Heterocyclic Carbene Complexes of Copper and Anthyridine-Based Dimetallic Complexes: Synthesis and Catalytic Application

林仕杰(Shih-Chieh Lin)

指導教授 ： 劉緒宗

國立臺灣大學/理學院/化學研究所/博士(2020年)

https://doi.org/10.6342/NTU202000044

摘要

本論文由兩部分所組成，第一部分為氮異環碳烯 (N-Heterocyclic Carbenes, NHCs) 錯合物之合成及催化應用；第二部分則為含氮多牙配位基之雙金屬錯合物 (同核與異核) 其合成、催化應用與雙金屬協同效應探討。氮異環碳烯因具有強σ-donating特性與不錯穩定性，於有機金屬錯合物合成與催化應用中，常被視為膦配位基 (phosphine ligand) 類似物而被廣泛使用，且經官能化修飾之NHCs錯合物，可有效提升於催化反應的適用性。本研究合成出具有陰離子醯胺及氮異環碳烯配位基之銅 (Ⅱ)金屬錯合物5a與5b，此 (C, N-, N) 異位多牙配位 (heterotopic multidentate) 型錯合物並將其應用於苯乙烯及1,3-二甲氧基苯之溴化反應，以溴化鋰為溴來源試劑，於氧氣一大氣壓下進行。5a與5b於催化溴化反應中，皆展現優越反應活性，與常見之單牙或多牙銅金屬錯合物有著明顯差異。推測是因錯合物5a與5b中，氮異環碳烯及陰離子醯胺基團具有高電子密度與給電子能力，可有效降低銅金屬之氧化電位，進而加速於溴陰離子氧化步驟中所形成之銅 (Ⅰ) 中間體重回銅 (Ⅱ)，以利於反應進行。
論文第二部分為雙金屬錯合物之合成及催化應用。以1,9,10-anthyridine為骨架之配位基16，可合成出雙釕金屬錯合物17及雙鈀金屬錯合物27-29。雙釕金屬錯合物17，可於水合聯胺為還原劑之條件下，進行硝基苯還原反應，且活性明顯高於單釕金屬錯合物，而cooperativity index α = 19，有明顯雙金屬協同效應。反應機構部分，錯合物17先將硝基苯還原至苯基羥胺，進一步還原至苯胺，過程中無生成亞硝基苯中間物。文獻報導中，僅有少數均相催化例子經由此反應途徑。同時，由測得之中間體錯合物質譜碎片，可更加了解雙釕金屬錯合物於此催化反應之協同效應機制。
於雙鈀金屬錯合物27-29中，27為三聚體錯合物 [(16)3Pd4(Cl)4](BF4)4，而 [(16)Pd2(MeCN)2(Cl)2](BF4)2 (28) 及 [(16)Pd2(MeCN)4](BF4)4 (29) 則同為單配位基之雙金屬錯合物；此外，可藉由調整配位基、鈀金屬與四氟硼酸銀之劑量，達到此三錯合物彼此間相互之轉換。於異核雙金屬部分，配位基16可與釕、鈀、銥及銠金屬合成出三種異核雙金屬錯合物Ru-Pd、Rh-Pd及Ir-Pd，並將其運用於4-苯乙酮之偶聯 (脫溴)/氫轉移聯繼催化反應。其中，Ru-Pd及Ir-Pd於此兩反應中，皆較其對應之單金屬錯合物具更佳催化活性；然而，Rh-Pd其活化碳-溴鍵之性質則明顯被抑制。此反應活性之差異，說明異核雙金屬其協同效應對此兩聯繼催化反應之影響。

關鍵字

氮異環碳烯 ； 多牙配位基錯合物 ； 協同效應 ； 三聚物 ； 聯繼催化反應

並列摘要

This thesis is divided into two parts. The first part of this thesis is about the synthesis of N-Heterocyclic Carbenes (NHCs) based complexes and their catalytic applications. The second part of this thesis describes the synthesis and the catalytic applications of multidentate homo- and hetero-dinuclear complexes, following by the discussion of their cooperative effects in catalysis.
NHCs have been widely used in organometallic chemistry and catalytic applications. Because of their strong σ-donating ability and high stability, NHCs are usually used as analogues of phosphine ligands in catalytic transformations. More applications in catalysis can also be achieved by functionalization of NHCs. In the first part of this thesis, we have synthesized the (C, N-, N) heterotopic multidentate Cu (Ⅱ) complexes 5a and 5b bearing NHC and amido functionality, which can be applied to catalytic bromination of styrene and 1,3-Dimethoxybenzene using LiBr as brominating reagent under O2 atmosphere. Complexes 5a and 5b are both efficient catalysts in the bromination reaction, whose reactivity are higher than common mono- or multidentate Cu (Ⅱ) complexes. We proposed that the high electron density and σ-donating properties of amido and NHC moiety of complex 5a and 5b reduce the oxidation potential of Cu (Ⅱ) center, facilitating the reoxidation of Cu (Ⅰ) intermediate formed in bromide ion oxidation step.
The second part of this thesis is about the synthesis of bimetallic complexes and their catalytic application. Here, we successfully synthesized the diruthenium complex 17 and dipalladium complexes 27-29 from the 1,9,10-anthyridine base ligand. The diruthenium complex 17 have the catalytic ability to reduce nitroarene using hydrazine hydrate as reducing agent, which is much higher than corresponding mononuclear ruthenium complex 18. The cooperativity index (α) of complex 17 is estimated to be 19, which implies the cooperative effect of this bimetallic system. In the reaction mechanism of this catalytic cycle, complex 17 first reduces nitroarene to phenylhydroxylamine without forming nitrosobenzene intermediate, and then phenylhydroxylamine is further reduced to aniline. Only rare examples of homogeneous system go through this reaction pathway were reported. The bimetallic cooperative effect in the catalytic mechanism can also be shown by the possible fragments of the intermediate obtained by ESI-MASS. We also successfully synthesized the dipalladium complexes [(16)3Pd4(Cl)4](BF4)4 (27)、[(16)Pd2(MeCN)2(Cl)2](BF4)2 (28) and [(16)Pd2(MeCN)4](BF4)4 (29). Complex 27 is a trimer with 3:4 ligand/metal stoichiometries, while complex 28 and 29 have the same ratio of ligand/metal stoichiometries (1:2). In addition, these three palladium complexes are interconvertible by tuning the amount of ligand、palladium ion and silver tetrafluoroborate. Furthermore, heterodimetallic complexes Ru-Pd、Rh-Pd and Ir-Pd could be synthesize and characterize. These complexes are applied to tandem reactions (debromination/transfer hydrogenation and Suzuki−Miyaura cross coupling/transfer hydrogenation). It was found that complexes Ru-Pd and Ir-Pd display higher catalytic activities when compared to equimolar mixtures of the corresponding mononuclear complexes. However, the activity of C-Br bond activation in complex Rh-Pd was inhibited. The difference of reactivity was presumed due to the bimetallic cooperative effect in these tandem catalysis.

並列關鍵字

N-Heterocyclic Carbene ； multidentate complexes ； cooperative effects ； trimer ； tandem catalysis

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