Coordination complexes of methimazole with copper: Controlling redox reactions and sulfur extrusion
Coordination complexes of methimazole with copper: Controlling redox reactions and sulfur extrusion
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DOI：
10.1016/j.ica.2020.119568
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发表时间：
2020-07
影响因子：
2.8
通讯作者：
Jaime M. Murphy;A. Gaertner;Amanda M. Owen;Samantha Struder;C. McMillen;M. Wetzler;Julia L. Brumaghim
中科院分区：
文献类型：
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作者：
Jaime M. Murphy;A. Gaertner;Amanda M. Owen;Samantha Struder;C. McMillen;M. Wetzler;Julia L. Brumaghim
含硫咪唑硫酮因其氧化还原化学和形成二硫键的倾向而引起人们的兴趣，使人想起生物活性二硫化物。在氧存在的情况下，用氧化还原活性的甲巯咪唑处理铜（II）会导致铜的同时还原和甲巯咪唑二硫的形成，并最终挤出其中一个硫原子。反应条件，包括化学计量学、氧的存在和金属离子的氧化还原状态，被改变以检查导致硫挤压的机理细节。六个独特的产品报道:[铜(κN, N-MMIMS) 2 (H2O) 2](就是HSO4) 2(铜(κN, N-MMIMS) 2 (H2O)] [CH3SO4][就是HSO4][水],[铜(κN, N-MMIMS) 2 (H2O)] (CH3SO4) 2(铜(κN, N-MMIMS)(κO, O-SO4) (CH3OH)],[铜(κN, N-MMIMS)(κO, O-SO4) (DMSO)]∙0.5 DMSO和[铜(μ,κO, O, O-SO4)(κN, N-MMIMS)] N [CH3CN] (MMIMS = bis (1-methylimidazol-2-yl)硫化)。在所有结构中，hso4和ch3so4反离子都是原位生成的。反应进行时的EPR分析表明，最初形成的四配位Cu2+-S配合物在反应过程中转变为方形平面或八面体Cu2+-N配位。利用DMPO作为自旋阱，通过EPR分析还观察到巯基自由基的形成。总之，这些结果建立了一个完整的硫挤压机制，通过铜-甲巯咪唑结合和氧化还原，超氧化物形成，水或甲醇对硫的亲核攻击，以及随后的亲核芳香取代来产生硫挤压产物。了解这一机理为脱硫和含硫聚合反应催化剂的开发奠定了基础。
Sulfur-containing imidazole thiones are of interest for their redox chemistry and tendency to form disulfide bonds reminiscent of biologically active disulfides. Treating copper(II) with redox-active methimazole in the presence of oxygen results in concomitant copper reduction and formation of methimazole disulfide, and ultimately, extrusion of one of the sulfur atoms. Reaction conditions, including stoichiometry, presence of oxygen, and redox state of the metal ion, were varied to examine the mechanistic details that lead to the sulfur extrusion. Six unique products are reported: [Cu(κN,N-MMIMS)2(H2O)2](HSO4)2, [Cu(κN,N-MMIMS)2(H2O)][CH3SO4][HSO4][H2O], [Cu(κN,N-MMIMS)2(H2O)](CH3SO4)2, [Cu(κN,N-MMIMS)(κO,O-SO4)(CH3OH)], [Cu(κN,N-MMIMS)(κO,O-SO4)(DMSO)]∙0.5 DMSO, and [Cu(μ,κO,O,O-SO4)(κN,N-MMIMS)]n[CH3CN] (MMIMS= bis(1-methylimidazol-2-yl)sulfide). In all structures, the HSO4-and CH3SO4-counterions are generatedin situ.EPR analysis of the reaction as it proceeds indicates initial formation of a four-coordinate Cu2+-S complex that shifts to square planar or octahedral Cu2+-N coordination over the course of the reaction. Formation of the thiyl radical is also observed by EPR analysis using DMPO as a spin trap. Together, these results establish a complete mechanism for sulfur extrusion that proceeds through copper-methimazole binding and redox, superoxide formation, and nucleophilic attack of water or methanol on sulfur, and subsequent nucleophilic aromatic substitution to yield the sulfur-extruded product. Understanding this mechanism lays the foundation for catalyst development for desulfurization and sulfur-containing polymerization reactions.