[Mn(tmc)(O2)]+ :: A side-on peroxido manganese(III) complex bearing a non-heme ligand
[Mn(tmc)(O2)]+ :: A side-on peroxido manganese(III) complex bearing a non-heme ligand
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DOI：
10.1002/anie.200603414
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发表时间：
2007-01-01
影响因子：
16.6
通讯作者：
Nam, Wonwoo
中科院分区：
文献类型：
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作者：
Seo, Mi Sook;Kim, Ja Young;Nam, Wonwoo
金属-O2配合物的化学在生物和生物无机化学界引起了极大的兴趣，因为这些物种是由金属酶和相应的模型化合物活化双氧的关键中间体。[1]在仿生研究中，已经合成了许多金属-O2加合物，并用各种光谱方法对其进行了表征，并且已经广泛研究了它们在有机底物氧化中的反应性。[2]例如，已合成了具有血红素和非血红素配体的过氧化物铁（III）络合物作为细胞色素P450芳香酶和Rieske双加氧酶的化学模型，并且已在各种亲核反应中证明了它们的反应性，例如醛脱氨。[3，4]最近已经合成和表征了过氧铜（III）和-镍-（III）配合物，但是它们在有机底物的氧化亲核反应中的反应性还没有很好地确定。[2d过氧化物锰（III）络合物也被用作含锰酶（如锰超氧化物歧化酶、过氧化氢酶和光系统II的放氧络合物）反应中的活性中间体。[6]在仿生学研究中，已经合成了许多锰-过氧化物配合物，并用包括X射线晶体学在内的各种光谱方法进行了表征。一个值得注意的例子是Valentine及其同事报道的第一个侧面上的过氧化物锰（III）卟啉络合物（[MnIII-（tpp）（O2）] nH3; tpp = meso-tetraphenylpyrrophin）的X射线晶体结构。[7]Kitajima等人报道了带有非卟啉配体的单体侧上过氧化物锰（III）络合物的第二晶体结构。[8]然而，过氧化物锰（III）配合物的反应性很少在氧化反应中进行研究。本文合成了一个带有大环四齿N_4配体[Mn Ⅲ-（tmc）（O_2）]~+（1; tmc = 1，4，8，11-四甲基-1，4，8，11-四氮杂环十四烷）的过氧化物锰（Ⅲ）配合物。1的X-射线晶体结构显示过氧化物配体以侧对η 2方式结合。在[Mn（tmc）（CF_3SO_3）_2]和三乙胺的溶液中加入5当量的H_2O_2，在258 ℃下，在CH3CN中，用乙酸乙酯（TEA; 2.5当量）洗脱，得到吸收带在453 nm处的绿色中间体1（ε = 490 m2/cm 2 - 1）和630 nm（ε = 120 m2/cm 2 - 1;图1a，实验详情见支持信息）。该中间体在258 ℃下持续数小时（t1/2%5 h）。1的电喷雾电离质谱（ESI-MS）在质荷比（m/z）为343.1处显示出显著离子峰（图1b），其质量和同位素分布模式对应于[Mn-（tmc）（O2）]+（计算的m/z为343.2;图1b，插图）。当用同位素标记的H2 18 O2进行反应时，对应于[Mn（tmc）（18 O2）]+的质量峰出现在m/z 347.1处（计算的m/z 347.2;图1b，插图）。用18O取代16O后增加4个质量单位
The chemistry of metal–O2 complexes has attracted much interest in the biological and bioinorganic chemistry communities, as such species are generated as key intermediates in the activation of dioxygen by metalloenzymes and corresponding model compounds.[1] In biomimetic studies, a number of metal–O2 adducts have been synthesized and characterized with various spectroscopic methods, and their reactivities in the oxidation of organic substrates have been extensively investigated.[2] For example, peroxidoiron (III) complexes with heme and non-heme ligands have been synthesized as chemical models of cytochrome P450 aromatase and Rieske dioxygenases, and their reactivities have been demonstrated in various nucleophilic reactions, such as aldehyde deformylation.[3, 4] Peroxidocopper (III) and-nickel-(III) complexes have been synthesized and characterized recently, but their reactivities have not been well established in oxidative nucleophilic reactions of organic substrates.[2d, e, 5] Peroxidomanganese (III) complexes are also invoked as reactive intermediates in the reactions of Mn-containing enzymes, such as manganese superoxide dismutase, catalase, and the oxygen-evolving complex of photosystemII.[6] In biomimetic studies, a number of Mn–peroxido complexes have been synthesized and characterized with a variety of spectroscopic methods including X-ray crystallography. A notable example is the first X-ray crystal structure of a side-on peroxido manganese (III) porphyrin complex ([MnIII-(tpp)(O2)] À; tpp= meso-tetraphenylporphyrin), reported by Valentine and co-workers.[7] The second crystal structure of a monomeric side-on peroxido manganese (III) complex bearing a non-porphyrinic ligand was reported by Kitajima et al.[8] However, reactivities of the peroxidomanganese (III) complexes have been rarely investigated in oxidation reactions. In the present work, we synthesized a peroxidomanganese (III) complex bearing a macrocyclic tetradentate N4 ligand,[MnIII-(tmc)(O2)]+(1; tmc= 1, 4, 8, 11-tetramethyl-1, 4, 8, 11-tetraazacyclotetradecane). The X-ray crystal structure of 1 shows the binding of a peroxido ligand in a side-on η2 fashion. We have also demonstrated that 1 is capable of conducting aldehyde deformylation by a nucleophilic reaction in which cyclohexanecarboxaldehyde is deformylated to give cyclohexene as a sole product.Addition of 5 equivalents of H2O2 to a solution containing [Mn (tmc)(CF3SO3) 2] and triethylamine (TEA; 2.5 equiv) in CH3CN at 258C afforded a green intermediate 1 with absorption bands at 453 nm (ε= 490mÀ1 cmÀ1) and 630 nm (ε= 120mÀ1 cmÀ1; Figure 1a, see the Supporting Information for experimental details). The intermediate persisted for several hours (t1/2% 5 h) at 258C. The electrospray ionization mass spectrum (ESI-MS) of 1 exhibits a prominent ion peak at a mass-to-charge ratio (m/z) of 343.1 (Figure 1b) whose mass and isotope distribution pattern corresponds to [Mn-(tmc)(O2)]+(calculated m/z 343.2; Figure 1b, inset). When the reaction was carried out with isotopically labeled H2 18O2, a mass peak corresponding to [Mn (tmc)(18O2)]+ appeared at m/z 347.1 (calculated m/z 347.2; Figure1b, inset). The 4-mass-unit increase upon the substitution of 16O with 18O