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  • 學位論文

含氮雜環二價鈀金屬錯化合物的合成,結構鑑定與催化應用探討

Synthesis, Characterization and Catalytic Applications of N-Heterocyclic Carbene Palladium(II) Complexes

指導教授 : 于淑君
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摘要


催化反應根據系統的溶解度可分成均相 (homogenous) 和非均相 (heterogeneous) 兩大類。鈀金屬被廣泛應用於均相和非均相催化反應上。其中,在鈀金屬均相催化反應中,經常使用PdCl2、 Pd(OAc)2 和 Pd(allyl)Cl2 三大系列鈀金屬做為催化劑。因此,在本論文中我們以PdCl2為起始物,成功合成二價鈀-含氮雜環碳烯化合物 [Pd(PPh3)2(Dmim)Cl][PF6] (6)、 Pd(pyridine)(Dmim)Cl2 (7) 與 Pd(CN)Cl2 (8),此三種化合物可以經由純化步驟單離,並以光譜分析確認其結構組成。單離後的固態粉末在空氣下可儲存一個禮拜且對有機溶劑具有高溶解度。而其合成步驟,簡述如下: Pd(PPh3)Cl2 和離子液體 (Dmim)HPF6 (2) 在 THF 中,加熱迴流 4 小時,即可得到白色固體 [Pd(PPh3)2(Dmim)Cl][PF6] (6)。而PdCl2 和離子液體 (Dmim)HPF6 (2) 在吡啶溶劑中,60 oC 下反應 6 小時,即可得到淡黃色固體 Pd(pyridine)(Dmim)Cl2 (7)。最後,使用3-decyl-1-picolylimidazolin-2-ylidene bromide (4) 與氧化銀,在二氯甲烷中,室溫下反應可得到白色固體的銀轉移試劑 [AgBr(CN)] (5)。接著,藉由[AgBr(CN)] (5) 與 Pd(CH3CN)2Cl2 在乙腈溶劑下進行碳烯轉移反應,可生成高產率的淡黃色固體 Pd(CN)Cl2 (8)。經純化步驟後,所得的化合物6、7和8可經由核磁共振儀、電噴灑游離質譜儀和傅立葉轉換紅外線光譜儀進行結構鑑定。其中化合物 Pd(CN)Cl2 (8) 的結構,為含氮雜環配位基上的碳烯和吡啶同時與中心金屬配位,形成雙螯合化合物。在化合物6和7的結構中,含氮雜環碳烯與中心金屬配位,形成單螯合化合物。 二價鈀具備優於其他金屬的催化活性,並擁有催化反應的多元性及選擇性。在本論文中,以[Pd(PPh3)2(Dmim)Cl][PF6] (6)、Pd(pyridine)(Dmim)Cl2 (7) 與 Pd(CN)Cl2 (8) 分別對 Heck、 Strecker、 Stille 和磺醯胺類化合物烯化反應進行催化活性探討發現皆有相當好的效果。其中,Heck 反應僅需0.25 mol% 催化劑 6 ,在15分鐘內即可達到85% 以上的產率。而催化劑 7 和8 進行選擇性Heck 反應,在不同極性溶劑系統下有較佳的的立體選擇性。在 Strecker反應中,使用 3 mol% 催化劑 6、 7 和 8,在無溶劑的情況下 10 分鐘內可達到93% 以上的產率。在 Stille 反應中,使用 2 mol% 催化劑 6、 7 和 8,在 55 oC、5 小時內可達到42 - 99 % 的產率;或藉由微波加熱大幅縮短反應時間,並達到相近的產率。最後,在磺醯胺類化合物烯化反應中,使用 2 mol% 催化劑 6、 7和 8,在 65 oC下,可達到64 - 99% 的產率。

關鍵字

催化

並列摘要


We have successfully synthesized palladium(II) N-heterocyclic carbene (NHC) complexes, [Pd(PPh3)2(Dmim)Cl][PF6] (6), Pd(pyridine)(Dmim)Cl2 (7) and Pd(CN)Cl2 (8) in quantitative yields, where Dmim is 1-decyl-3-methylimidazolium and (C^N) is 3-decyl-1-picolylimidazolin-2-ylidene. A solution of (Dmim)HPF6 (2) in THF was treated with Pd(PPh3)Cl2 at reflux for 4 hr to give NHC-complex, [Pd(PPh3)2(Dmim)Cl][PF6] (6) as white solid. Whereas a solution of (Dmim)HPF6 (2) in pyridine was treated with PdCl2 at 60 oC for 6 hour to afford Pd(pyridine)(Dmim)Cl2 (7) as yellow solid. Similary, a solution of 3-decyl-1-picolylimidazolin-2-ylidene bromide (4) in CH2Cl2 was treated with Ag2O at ambient temperature to afford transfer agent [AgBr(CN)] (5). The complex Pd(CN)Cl2 (8) can be synthesized as yellow solid by the direct reaction of Pd(CH3CN)2Cl2 with [AgBr(CN)] (5). All the complexes 6, 7 and 8 were characterized by NMR, MS and IR spectroscopies. It was found that only the strcucture of Pd(CN)Cl2 (8) is a CN bidentate complex, and both 6 and 7 were 4-coordinated Pd supported by monodentate NHC ligand. Palladium has been known to exbihit extremely effective catalytic activity, diversity and selectivity than other transition metals. In the current study, we have demonstrated that all three N-heterocyclic carbene-Pd complexes 6, 7 and 8 exhibited excellent catalytic reactivity towards a series Heck-, Strecker-, Stille coupling and N-vinylation of various sulfonamides reactions. For example, only with a catalyst loading of as little as 0.25 mol% 6-catalyzed Heck arylation reactions could be completed in 15 min to give high yields of desired products. All three Pd complexes were also studied for the stereoselectivity in Heck reaction of electron rich olefin. It was found that 7 and 8 are better in control the stereoselectivity by varying the solvent of polarity. In Strecker reactions, with a catalyst loading of 3 mol% of 6, 7 and 8 under solventless conditions can afford high yields of products in 10 min. In Stille reactions, with a catalyst loading of 2 mol% of 6, 7 and 8 at 55 oC for 5 hr gave desired products in high yields (42 – 99 %). In addition, Stille reaction can be further accelerated under microwave irradiation conditions. Finally, in N-vinylation reaction of various sulfonamides, with a catalyst loading of 2 mol% of 6, 7 and 8 at 65 oC afforded products in good yields (64 - 99 %).

並列關鍵字

catalyst

參考文獻


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