(I)微粒體甲烷單氧化酵素之結構與功能性模型三核銅金屬簇化物之研究 (II)似單氧化酵素之三核錳金屬簇化物對烷類分子氧化催化之研究

(I)Structrual and Functional Models for the Trinuclear Copper Clusters of the Particulate Methane Monooxygenase (II)Monooxygenase-like Oxygenation of Alkane Molecules Catalyzed by Trinuclear Manganese Complex

簡佑芩

指導教授 ： 陳炳宇

國立臺灣師範大學/理學院/化學系/碩士(2011年)

摘要

在第一個研究中，我們成功合成一新穎的三核銅金屬簇離子化合物 [CuICuICuI(7-dipy)](BF4) (2)，可成功催化氧化環己烷的 CH 鍵 (CH 鍵能為 99.3 kcal mol-1)。並藉由 ESI-MS 光譜證實經氧氣可得穩定的三核銅金屬簇含氧離子化合物 [CuIICuII(-O)CuII(7-dipy)](BF4)2 (3)。在室溫、常壓下利用 50 當量的 H2O2 催化氧化環己烷的 CH 鍵，根據 GC-MS 光譜定量分析及氧化劑的消耗量，可得轉換率 34% 的環己醇和環己酮的混合產物。然而，當利用 [CuIICuII(-O)CuII(7-dipy)](BF4)2 (3) 化合物取代 [CuICuICuI(7-dipy)](BF4) (2) 在相同反應條件下對氧化環己烷是幾乎沒有反應的。此外，[CuICuICuI(7-dipy)](BF4) (2) 進行催化反應後，仍可由 ESI-MS 光譜確認也可得到 [CuIICuII(-O)CuII(7-dipy)](BF4)2 (3) 化合物，證實此三核銅金屬簇離子化合物是一相當強健的催化劑。
在第二個研究中，我們利用相同的 7-dipy 配位基成功合成三核錳金屬簇離子化合物，首先合成出 [MnII(OAc)2MnII(-OAc)2MnII(7-dipy)] (2) 作為高價態的錳金屬簇離子化合物的前驅物。接著，藉由二當量 TBHP (tert-butylhydroperoxide)氧化 [MnII(OAc)2MnII(-OAc)2MnII(7-dipy)] (2) 可得一組 16 根特徵吸收之 EPR 光譜，由模擬軟體可得 gx= 2.006, gy= 1.998, gz= 1.985, AIIIxx= -16.3 mT, AIIIyy= -11.7 mT, AIIIzz= -16.2 mT, AIVxx= 8.2 mT, AIVyy= 8.0 mT, AIVzz= 7.4 mT，在此假定得到一活性中間體 [MnIIIMnIII(-O)2MnIV(7-dipy)]4+ (3) 化合物。當加入過量的 TBHP 至 15 當量時，仍可看到16 根特徵吸收之 EPR 光譜。 [MnIIIMnIII(-O)2MnIV(7-dipy)]4+ (3) 可催化氧化環己烷 (CH 鍵能為 99.3 kcal mol-1) 得到環己醇和環己酮的混合產物，亦可氧化正己烷的第二號及第三號碳位置上的 CH 鍵 (CH 鍵能分別為 98 kcal mol-1 和 99.1 kcal mol-1) 可得2-己醇、3-己醇、2-己酮、3-己酮的混合產物。此催化劑除了氧化二級碳 (secondary carbon) 上的 CH 鍵外，利用乙烷當作受質，可氧化一級碳上的CH 鍵 (CH 鍵能為 101 kcal mol-1)，得到 6 個氧化當量的乙酸產物。利用同樣的催化劑以乙醇當作受質，也會被氧化形成乙酸產物，為氧化乙烷分子的間接佐證。

關鍵字

三核銅 ； 三核錳

並列摘要

In first study, a new modified trinuclear copper complex,
[CuICuICuI(7-dipy)](BF4) (2), was first employed as a catalyst to oxidize the CH bonds of cyclohexane (CH BDE is 99.3 kcal mol-1). ESI-MS spectra demonstrate that the oxygenation of [CuICuICuI(7-dipy)](BF4) (2)either by dioxygen will obtain a stable [CuIICuII(-O)CuII(7-dipy)](BF4 )2(3) complex. The catalysis of CH bond oxygenation of cyclohexane was carried out under room temperature in the presence of 50 equivalents of oxidant, and a product mixture of cyclohexanol and cyclohexanone were observed with 34% conversion according to the consuming of the oxidant by the quantitative GC-MS analysis. However, there is nearly no reaction by employing [CuIICuII(-O)CuII(7-dipy)](BF4)2 (3) complex instead of [CuICuICuI(7-dipy)](BF4) (2). This tricopper complex is a quite robust catalyst because most the remainders after the catalytic reaction are in the form of [CuIICuII(-O)CuII(7-dipy)](BF4)2 (3)evidenced by ESI-MS spectra.
In second study, the same 7-dipy ligand was also adopted in the synthesis of trinuclear manganese complex. A first trimanganese complex [MnII(OAc)2MnII(-OAc)2MnII(7-dipy)] (2) was first synthesized as a precursor for the high-valent manganese species. Further oxidation of [MnII(OAc)2MnII(-OAc)2MnII(7-dipy)] (2) by treating two equivalents of TBHP (tert-butylhydroperoxide) is able to obtain a 16-line characteristic EPR spectrum with gx= 2.006, gy= 1.998, gz= 1.985, AIII xx=-16.3 mT, AIII yy= -11.7 mT, AIII zz= -16.2 mT, AIV xx= 8.2 mT, AIV yy= 8.0 mT, AIV zz= 7.4 mT acquired by simulation, which is postulated as a active intermediate, [MnIIIMnIII(-O)2MnIV(7-dipy)]4+ (3). While excess of TBHP up to 15 equivalents were added, and the 16-line EPR spectra still remain unchanged. [MnIIIMnIII(-O)2MnIV(7-dipy)]4+ (3) is able to catalyze the oxidation of CH bonds of cyclohexane (CH BDE is 99.3 kcal mol-1) to a mixture of cyclohexanol and cyclohexanone, CH bonds of n-hexane in the C-2 and C-3 position (CH BDE is 98 kcal mol-1 and 99.1 kcal mol-1, respectively) to a mixture of 2-hexanol, 3-hexanol, 2-hexanone and 3-hexanone. Except the CH bond oxidation in the secondary carbon atom position, ethane molecule which merely has primary CH bonds (CH BDE is 101 kcal mol-1) was applied as the substrate, and the suspected acetic acid product involving 6 oxidation equivalents was found. Ethanol molecule (CH BDE is 95.6 kcal mol-1) as the substrate was also oxidized in the same catalysis to form the acetic acid product, providing the support for the oxidation of ethane molecule.

參考文獻

1. Periana, R. A.; Bhalla, G.; Tenn, W. J.; Young, K. J. H.; Liu, X. Y.; Mironov, O.; Jones, C. J.; Ziatdinov, V. R., Perspectives on some challenges and approaches for developing the next generation of selective, low temperature, oxidation catalysts for alkane hydroxylation based on the CH activation reaction. J. Mol. Catal. A-Chem. 2004, 220 (1), 7-25.

2. Shindell, D. T.; Faluvegi, G.; Koch, D. M.; Schmidt, G. A.; Unger, N.; Bauer, S. E., Improved Attribution of Climate Forcing to Emissions. Science 2009, 326 (5953), 716-718.

4. Chan, S. I.; Chen, K. H. C.; Yu, S. S. F.; Chen, C. L.; Kuo, S. S. J., Toward delineating the structure and function of the particulate methane monooxygenase from methanotrophic bacteria. Biochemistry 2004, 43 (15), 4421-4430.

5. Feig, A. L.; Lippard, S. J., Reactions of Nonheme Iron(Ii) Centers with Dioxygen in Biology and Chemistry. Chem. Rev. 1994, 94 (3), 759-805.

6. Lipscomb, J. D., Biochemistry of the Soluble Methane Monooxygenase. Annu. Rev. Microbiol. 1994, 48, 371-399.