Homogeneous catalytic oxidation of thymol with dinuclear Cu(II)-2-phenyl propionate-bipyridine complex

IF 2.4 3区化学 Q2 CHEMISTRY, INORGANIC & NUCLEAR

Polyhedron Pub Date : 2024-11-20 DOI:10.1016/j.poly.2024.117312

İbrahim Kani

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Abstract

A carboxylate-bridged dinuclear copper(II) complex, [Cu₂(μ₂-η²:η¹(ppa)₂(μ₂-η¹:η¹ (ppa)bpy)₂]·ClO₄·H₂O (ppa (C₉H₉OO) = 2-phenyl propionate, bpy = 2,2′-bipyridine), was prepared and its structure was determined by X-ray diffraction analysis. The octacoordinated Cu(II) dimer complex exhibits an asymmetric conformation, with the metal centers linked by two distinct modes of the carboxylate group. These include an asymmetric chelating bridging bidentate involving two ppa ligands and a syn-syn bidentate bridging mode involving one ppa ligand. The complex was employed as a catalyst for the oxidation of thymol, demonstrating a high degree of quantitative conversion and selectivity with TBHP across a range of solvents at moderate temperatures. The homogeneous catalytic system, comprising Cu(II)-2-phenyl propionate-bipyridine, tert-butylhydroperoxide (TBHP) as oxidant, and a polar aprotic solvent (acetonitrile or acetone), demonstrated high turnover numbers (TOF) in the absence of any additives. The impact of temperature, solvent, the ratio of thymol to TBHP, different oxidants and the quantity of catalyst on the catalytic activity and product selectivity was examined. Under optimized conditions, the maximum conversion of thymol (100 %) was obtained with 100 % selectivity to thymoquinone with TBHP after 35 min at the thymol to catalyst mole ratio of 267 (TOF = 449 h⁻¹) in acetonitrile (MeCN) at 55 °C. Based on the available evidence, this activity and selectivity to thymoquinone represent the highest reported level of performance achieved by a homogeneously copper-catalysed process.

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双核Cu(II)-2-苯基丙酸-联吡啶配合物均相催化氧化百里香酚

制备了一种羧酸桥接双核铜（II）配合物[Cu2(μ2-η2:η1(ppa)2(μ2-η1:η1 (ppa)bpy)2]·ClO4·H2O （ppa (c9h900) = 2-苯基丙酸酯，bpy = 2,2′-联吡啶），并用x射线衍射分析确定了其结构。八配位Cu（II）二聚体配合物具有不对称构象，其金属中心由羧酸基的两种不同模式连接。这些包括涉及两个ppa配体的不对称螯合桥接双齿和涉及一个ppa配体的同步-同步双齿桥接模式。该配合物被用作百里香酚氧化的催化剂，在中等温度下，在一系列溶剂中显示出高度的定量转化和选择性。均相催化体系由Cu(II)-2-苯基丙酸-联吡啶、叔丁基过氧化氢（thbhp）作为氧化剂和极性非质子溶剂（乙腈或丙酮）组成，在没有任何添加剂的情况下表现出较高的周转率（TOF）。考察了温度、溶剂、百里酚与三必和二酚的比例、不同氧化剂和催化剂用量对催化活性和产物选择性的影响。在此条件下，在55℃乙腈中，百里香酚与催化剂摩尔比为267 (TOF = 449 h−1)，百里香酚与thbhp反应35 min后，百里香酚的转化率为100%，选择性为100%。根据现有的证据，这种活性和对百里醌的选择性代表了报道的铜均质催化过程所达到的最高性能水平。

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来源期刊

Polyhedron 化学-晶体学

CiteScore

4.90

自引率

7.70%

发文量

515

审稿时长

2 months

期刊介绍： Polyhedron publishes original, fundamental, experimental and theoretical work of the highest quality in all the major areas of inorganic chemistry. This includes synthetic chemistry, coordination chemistry, organometallic chemistry, bioinorganic chemistry, and solid-state and materials chemistry. Papers should be significant pieces of work, and all new compounds must be appropriately characterized. The inclusion of single-crystal X-ray structural data is strongly encouraged, but papers reporting only the X-ray structure determination of a single compound will usually not be considered. Papers on solid-state or materials chemistry will be expected to have a significant molecular chemistry component (such as the synthesis and characterization of the molecular precursors and/or a systematic study of the use of different precursors or reaction conditions) or demonstrate a cutting-edge application (for example inorganic materials for energy applications). Papers dealing only with stability constants are not considered.