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首页> 外文期刊>Chemistry: A European journal >Heterolytic Cleavage of Peroxide by a Diferrous Compound Generates Metal-Based Intermediates Identical to Those Observed with Reactions Utilizing Oxygen-Atom-Donor Molecules
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Heterolytic Cleavage of Peroxide by a Diferrous Compound Generates Metal-Based Intermediates Identical to Those Observed with Reactions Utilizing Oxygen-Atom-Donor Molecules

机译：二铁化合物对过氧化物的异质裂解产生的金属中间体与利用氧原子给体分子反应观察到的中间体相同

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摘要

Under cryogenic stopped-flow conditions, addition of 2-methyl-1-phenylprop-2-yl hydroperoxide (MPPH) to the diiron(II) compound, [Fe-2(H(2)Hbamb)(2)(NMelM)(2)] (1; NMelm = N-methylimidazole, H(4)HBamb: 2,3-bis(2-hydroxybenzamido)dimethyl-butane) results in heterolytic peroxide O-O bond cleavage, forming a high-valent species, 2. The UV/Vis spectrum of 2 and its kinetic behavior suggest parallel reactivity to that seen in the reaction of 1 with oxygen-atom-donor (OAD) molecules, which has been reported previously. Like the interaction with OAD molecules, the reaction of 1 with MPPH proceeds through a three step process, assigned to oxygen-atom transfer to the iron center to form a high-valent intermediate (2), ligand rearrangement of the metal complex, and, finally, decay to a diferric mu-oxo compound. Careful examination of the order of the reaction with MPPH reveals saturation behavior. This, coupled with the anomalous non-Arrhenius behavior of the first step of the reaction, indicates that there is a preequilibrium peroxide binding step prior to O-O bond cleavage. At higher temperatures, the addition of the base, proton sponge, results in a marked decrease in the rate of O-O bond cleavage to form 2; this is assigned as a peroxide deprotonation effect, indicating that the presence of protons is an important factor in the heterolytic cleavage of peroxide. This phenomenon has been observed in other iron-containing enzymes, the catalytic cycles of which include peroxide O-O bond cleavage.
机译：在低温停止流动条件下，将2-甲基-1-苯基丙-2-基氢过氧化物（MPPH）添加到二铁（II）化合物[Fe-2（H（2）Hbamb）（2）（NMelM）（ 2）]（1; NMelm = N-甲基咪唑，H（4）HBamb：2，3-双（2-羟基苯甲酰胺基）二甲基丁烷）导致杂合的过氧化物OO键裂解，形成高价物质2。 2的UV / Vis光谱及其动力学行为表明与1与氧原子供体（OAD）分子的反应具有相似的反应性，这已在之前进行了报道。像与OAD分子的相互作用一样，1与MPPH的反应通过三步过程进行，该过程涉及氧原子转移至铁中心以形成高价中间体（2），金属配合物的配体重排，以及最后，衰减成二价的mu-oxo化合物。仔细检查与MPPH的反应顺序可发现饱和行为。这与反应第一步的异常非阿累尼乌斯行为有关，表明在O-O键断裂之前有一个过平衡的过氧化氢结合步骤。在较高的温度下，添加碱，质子海绵会导致O-O键断裂形成2的速率明显降低;这归因于过氧化物的去质子化作用，表明质子的存在是过氧化物的杂化裂解的重要因素。在其他含铁酶中也观察到这种现象，其催化循环包括过氧化物O-O键裂解。

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