A novel thermally stable hydroperoxo-copper(II) complex in a Cu(N2O2) chromophore of a potential N4O2 donor Schiff base ligand: synthesis, structure and catalytic studies
A novel thermally stable hydroperoxo-copper(II) complex in a Cu(N2O2) chromophore of a potential N4O2 donor Schiff base ligand: synthesis, structure and catalytic studies
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DOI：
10.1039/c3dt51359a
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发表时间：
2013-01-01
影响因子：
4
通讯作者：
Ali, Mahammad
中科院分区：
文献类型：
--
作者：
Biswas, Surajit;Dutta, Arpan;Ali, Mahammad
金属-氢过氧/金属-过氧（LCuII-OOH或LCuII-OO中心点）配合物的生成和研究是许多化学和生化研究人员的一个迷人的研究领域，因为它们作为活性中间体参与了许多生物和工业催化氧化过程。为此，我们设计了一个体积庞大的六配位配体，具有潜在的N4O2供体原子，可以为合成单核Cu（II）配合物提供机会，目的是利用它在环境友好的氧化剂H2O2催化氧化芳烃。对Cu（II）配合物(1)进行了结构表征，发现其具有方形平面几何结构，两个吡唑基保持悬垂模式。在Et3N存在下，1与H2O2反应生成了一种新的单核配合物[Et3NH][LCuII-OOH](2)。通过ESI-MS+和MS- (m/z)质量分析和DFT计算证实，这些悬空基团的存在有利于氢过氧物质[LCu-OOH](-)(2)与配位的苯氧氧原子成氢键的稳定性。该配合物在室温下是热稳定的[k(d) = (5.67 +/- 0.03) x 10(-5) s(-1) 25℃]，这可能是由于DFT计算所描绘的O-O- h中心点中心点O（phenoxo）氢键的形成。配合物1是芳烃以2:1摩尔比氧化生成相应醛和醇的有效催化剂，TON接近300。
The generation and study of metal-hydroperoxo/metal-peroxo (LCuII-OOH or LCuII-OO center dot) complexes is a fascinating area of research of many chemical and biochemical researchers, because of their involvement as active intermediates in many biological and industrial catalytic oxidation processes. For this purpose we have designed a bulky hexa-coordinating ligand with potential N4O2 donor atoms which could provide an opportunity to synthesize a mononuclear Cu(II) complex with an aim to utilize it in the catalytic oxidation of aromatic hydrocarbons by an environmentally benign oxidant, H2O2. The Cu(II) complex (1) was structurally characterized and found to have square-planar geometry with the two pyrazolyl groups remaining in dangling mode. A novel mononuclear complex [Et3NH][LCuII-OOH] (2) was found to form in the reaction between 1 and H2O2 in the presence of Et3N. The presence of this dangling groups favours the stability of hydroperoxo species, [LCu-OOH](-) (2) through H-bonding with the coordinated phenoxo oxygen atom, which was confirmed by ESI-MS+ and MS- (m/z) mass analysis and DFT calculations. This complex was found to be thermally stable at room temperature [k(d) = (5.67 +/- 0.03) x 10(-5) s(-1) at 25 degrees C] and may be due to the formation of O-O-H center dot center dot center dot O(phenoxo) H-bonding as delineated by the DFT calculations. Complex 1 was found to be an efficient catalyst for the oxidation of aromatic hydrocarbons to the corresponding aldehyde and alcohol in 2 : 1 mole ratio with TON similar to 300.