| 摘要: | 在我們最近DFT計算的結果指出，三核銅簇合物bis(μ3-oxo)trinuclear copper(II, II, III) complex的結構能夠調控一個singlet “oxene”。它被用來模擬一個能輕易對甲烷，或是低碳數的碳氫化合物進行hydroxylation反應的重要膜蛋白酵素，—甲烷單氧化酵素(pMMO)—，其中的一個催化中心(C-cluster）。我們設計並合成了一系列能夠配位三個銅離子的配位基作為模擬分子來模仿這個反應。在質譜分析中，氧化[Cu3(I, I, I)L](X) complexes將形成相對應的[Cu3(II, II, II)L(O)](X)2 complexes。只有一個氧原子停留在trinuclear copper(II, II, II) complex上。當[Cu3(II, II, II)L(O)](X)2 complex在CH3CN中加入了三當量的benzoin和triethylamine並通入氧氣，benzoin氧化成為benzil後再進一步的被氧化並水解成為兩分子的benzoic acid。藉由18O2同位素標記以及GC-MS的分析，證實了bis (μ3-oxo)trinuclear copper(II, II, III) complex有效率的調控對benzil的oxo-transfer。我們提出一個關於bis(μ3-oxo)Cu(II)Cu(II)Cu(III) trinuclear copper intermediate對benzil分子間進行碳—碳鍵oxo-insertion的反應機制。 Recent DFT electronic calculations of a trinuclear copper cluster bis(?3-oxo)trinuclear copper(II, II, III) complex have showed that this structure harnesses a singlet “oxene”, mimicking one of the C-clusters in the particulate methane monooxygenase (pMMO), an important membrane enzyme that mediate the facile hydroxylation of methane and other small hydrocarbons. A series of supporting ligands that are capable to trap three copper ions toward developing a model compound to mimic this chemistry, we have designed and synthesized. Oxygenation of their corresponding [Cu3(I, I, I)L](X) complexes of these ligands leads to the formation of [Cu3(II, II, II)L(O)](X)2 (L = 7-Et, 7-Me, 6-Et, 6-Me; X = ClO4- and BF4-) through mass spectrometry analysis. Only one oxygen atom is locked in the trinuclear copper(II, II, II) complex. When the [Cu3(II, II, II)L(O)](X)2 complex is treated with three equivalent amounts of benzoin and triethylamine in CH3CN, and the solution purged by dioxygen, the benzoin is oxidized to benzil, which in turn is cleaved by further oxidation and hydrolyzes to 2 benzoic acid molecules. This chemistry is mediated by efficient oxo-transfer from the bis(μ3-oxo)trinuclear copper(II, II, III) complex to the benzil, as verified by 18O2 isotope labeling experiments and subsequent GC-MS analysis. We propose a mechanism involving intermolecular oxo-insertion across the C-C bond of the benzil by the bis(μ3-oxo)Cu(II)Cu(II)Cu(III) trinuclear copper intermediate. |
