多牙氮配位基及雙鈀金屬錯合物的性質和催化反應的探討

Study on Catalytic Hydrogenation Using Dipalladium Complexes with a Multidentate Ligand

沈芃(Peng Shen)

指導教授 ： 劉緒宗

國立臺灣大學/理學院/化學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201802815

摘要

本篇論文探討多牙氮配位基2,7-bis(2-pyridyl)-1,8-naphthyridine (bpnp)和鈀金屬所形成的雙鈀金屬錯合物，並研究錯合物的結構及其催化還原的應用。將配位基bpnp和Pd(CH3CN)4(BF4)2在二甲基甲醯胺於室溫下反應，可生成雙鈀金屬錯合物[Pd2(bpnp)(μ-OH)(DMF)2](BF4)3 (M1)。在配位化學的探討中可發現，鈀金屬上的二甲基甲醯胺是一個很弱的配位基，在室溫中容易被氯離子取代而形成金屬錯合物[Pd2(bpnp)(μ-OH)Cl2]Cl。
使用錯合物M1作為催化劑，可在一大氣壓的氫氣下進行α,β-不飽和硝基化合物的還原反應。在不加入任何添加劑的情況下，可得到約六成的胺類化合物，不過在加入了少量的硼氫化鈉之後可有效地將胺類化合物的產率提升至近九成。另外若將反應溫度下降至室溫則會以酮肟化合物 (ketone oxime)為主要產物。經過動力學實驗發現，所得胺類產物並非由酮肟轉化而來，而是由硝基烷類化合物還原所得，說明胺和酮肟應是經由不同反應機制所得。在對α,β-不飽和硝基化合物的適用性進行探討時發現，胺和酮肟的選擇性應和取代基團的大小有關。此外，錯合物M1亦可用來催化其他官能基的還原反應，例如吲哚和α,β-不飽和羰基化合物的選擇性還原。

關鍵字

氫化 ； 雙鈀 ； 協同效應 ； α,β-不飽和硝基化合物 ； 還原

並列摘要

The naphthyridine-based multidentate ligand, 2,7-bis(2-pyridyl)-1,8-naphthyridine (bpnp), is an excellent ligand for accommodation of bimetallic systems. Substitution of Pd(CH3CN)4(BF4)2 with bpnp in dimethylformamide (DMF) at room temperature yielded the dipalladium complex [Pd2(bpnp)(μ-OH)(DMF)2](BF4)3 (M1), which was characterized by X-ray crystallographic and spectroscopic methods. Coordination study showed that the weak coordinating DMF was easily replaced by a chloride at ambient temperature to render [Pd2(bpnp)(OH)Cl2]Cl.
Complex M1 displays a good activity on catalytic hydrogenation of various substrates under atmospheric pressure of hydrogen. The complex catalyzes the reduction of nitroalkenes at refluxing temperature in methanol to yield about 60% amines. By addition of catalytic amount of NaBH4 and running at similar reaction condition, reaction provides amines to ca. 90%. On the other hand, lowering the reaction temperature to 30oC yields the corresponding oxime as major product. Control experiments indicated that the oxime compound does not convert into the corresponding amine, suggesting two independent pathways leading to these products. In addition, the selective hydrogenation reaction of indole and α,β-unsaturated carbonyl compounds can also be catalyzed via this dipalladium complex.

並列關鍵字

hydrogenation ； dipalladium ； synergstic effect ； nitroalkene ； reduction

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