Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Inorg Chem. 2012 Oct 1;51(19):10417-26. doi: 10.1021/ic301642w. Epub 2012 Sep 12.
Oxygenation of a diiron(II) complex, Fe(II)(2)(μ-OH)(2)(BnBQA)(2)(NCMe)(2) [2, where BnBQA is N-benzyl-N,N-bis(2-quinolinylmethyl)amine], results in the formation of a metastable peroxodiferric intermediate, 3. The treatment of 3 with strong acid affords its conjugate acid, 4, in which the (μ-oxo)(μ-1,2-peroxo)diiron(III) core of 3 is protonated at the oxo bridge. The core structures of 3 and 4 are characterized in detail by UV-vis, Mössbauer, resonance Raman, and X-ray absorption spectroscopies. Complex 4 is shorter-lived than 3 and decays to generate in ~20% yield of a diiron(III/IV) species 5, which can be identified by electron paramagnetic resonance and Mössbauer spectroscopies. This reaction sequence demonstrates for the first time that protonation of the oxo bridge of a (μ-oxo)(μ-1,2-peroxo)diiron(III) complex leads to cleavage of the peroxo O-O bond and formation of a high-valent diiron complex, thereby mimicking the steps involved in the formation of intermediate X in the activation cycle of ribonucleotide reductase.
二铁(II)配合物Fe(II)(2)(μ-OH)(2)(BnBQA)(2)(NCMe)(2) [2]的氧化作用导致形成亚稳态过氧二铁(III)中间产物 3。用强酸处理 3 得到其共轭酸 4，其中 3 的(μ-氧)(μ-1,2-过氧)二铁(III)核在氧桥处质子化。通过紫外可见光谱、穆斯堡尔光谱、共振拉曼光谱和 X 射线吸收光谱详细表征了 3 和 4 的核心结构。4 的寿命比 3 短，会衰减生成约 20%的二铁(III/IV)物种 5，这可以通过电子顺磁共振和穆斯堡尔光谱鉴定。该反应序列首次证明，(μ-氧)(μ-1,2-过氧)二铁(III)配合物中氧桥的质子化导致过氧 O-O 键的断裂和高价二铁配合物的形成，从而模拟了核苷酸还原酶激活循环中中间 X 形成过程中涉及的步骤。
