Institut de Recherches sur la Catalyse et l'Environnement de Lyon (IRCELYON), UMR 5256, CNRS-Université Lyon, 2, av. A. Einstein, 69626 Villeurbanne, Cedex, France.
Dalton Trans. 2011 Jan 21;40(3):701-10. doi: 10.1039/c0dt00958j. Epub 2010 Nov 11.
N-bridged diiron tetra-tert-butylphthalocyanine activates H(2)O(2) to form anionic hydroperoxo complex (Pc)Fe(IV)=N-Fe(III)(Pc)-OOH prone to heterolytic cleavage of O-O bond with the release of OH(-) and formation of neutral diiron oxo phthalocyanine cation radical complex, PcFe(IV)=N-Fe(IV)(Pc(+)˙)=O. ESI-MS data showed stability of the Fe-N-Fe binuclear structure upon formation of this species, capable of oxidizing methane and benzene via O-atom transfer. The slow formation kinetics and the high reactivity preclude direct detection of this oxo complex by low temperature UV-vis spectroscopy. However, strong oxidizing properties and the results of EPR study support the formation of PcFe(IV)=N-Fe(IV)(Pc(+)˙)=O. Addition of H(2)O(2) at -80 °C led to the disappearance of iron EPR signal and to the appearance of the narrow signal at g = 2.001 consistent with the transient formation of PcFe(IV)=N-Fe(IV)(Pc(+)˙)=O. In the course of this study, another high valent diiron species was prepared in the solid state with 70% yield. The Mössbauer spectrum shows two quadrupole doublets with δ(1) = -0.14 mm s(-1), ΔE(Q1) = 1.57 mm s(-1) and δ(2) = -0.10 mm s(-1), ΔE(Q2) = 2.03 mm s(-1), respectively. The negative δ values are consistent with formation of Fe(iv) states. Fe K-edge EXAFS spectroscopy reveals conservation of the diiron Fe-N-Fe core. In XANES, an intense 1s → 3d pre-edge feature at 7114.4 eV suggests formation of Fe(iv) species and attaching of one oxygen atom per two Fe atoms at the 1.90 Å distance. On the basis of Mössbauer, EPR, EXAFS and XANES data this species was tentatively assigned as (Pc)Fe(IV)=N-Fe(IV)(Pc)-OH which could be formed from PcFe(IV)=N-Fe(IV)(Pc(+)˙)=O by hydrogen atom abstraction from a solvent molecule. Thus, despite unfavourable kinetics, we succeeded in the preparation of the first dirion(iv) phthalocyanine complex with oxygen ligand, generated in the (Pc)Fe(IV)=N-Fe(III)(Pc) - H(2)O(2) system capable of oxidizing methane.
N-桥联二铁四叔丁基酞菁能激活 H(2)O(2)形成阴离子过氧配合物(Pc)Fe(IV)=N-Fe(III)(Pc)-OOH，易发生 O-O 键异裂，释放 OH(-)并形成中性二铁氧酞菁阳离子自由基配合物 PcFe(IV)=N-Fe(IV)(Pc(+)˙)=O。ESI-MS 数据表明，该物种形成时 Fe-N-Fe 双核结构稳定，能够通过氧原子转移氧化甲烷和苯。缓慢的形成动力学和高反应性使得通过低温紫外可见光谱无法直接检测到这种过氧配合物。然而，强氧化性质和 EPR 研究的结果支持 PcFe(IV)=N-Fe(IV)(Pc(+)˙)=O 的形成。在-80°C 下添加 H(2)O(2)导致铁 EPR 信号消失，并出现 g = 2.001 的窄信号，与瞬态形成的 PcFe(IV)=N-Fe(IV)(Pc(+)˙)=O 一致。在本研究过程中，另一种高价二铁物种以 70%的产率在固态中制备。穆斯堡尔谱显示两个具有 δ(1) = -0.14 mm s(-1)，ΔE(Q1) = 1.57 mm s(-1)和 δ(2) = -0.10 mm s(-1)，ΔE(Q2) = 2.03 mm s(-1)的四极子双峰，分别。负 δ 值与 Fe(iv)态的形成一致。Fe K 边 EXAFS 光谱揭示了二铁 Fe-N-Fe 核的保持。在 XANES 中，7114.4 eV 处强烈的 1s → 3d 预边特征表明形成 Fe(iv)物种，并在 1.90 Å 距离处每个 Fe 原子附着一个氧原子。基于穆斯堡尔、EPR、EXAFS 和 XANES 数据，该物质被暂时指定为(Pc)Fe(IV)=N-Fe(IV)(Pc)-OH，它可以由 PcFe(IV)=N-Fe(IV)(Pc(+)˙)=O 通过从溶剂分子中提取氢原子形成。因此，尽管动力学不利，我们仍成功制备了具有氧配体的第一个二价(iv)酞菁配合物，该配合物在(Pc)Fe(IV)=N-Fe(III)(Pc) - H(2)O(2)体系中生成，能够氧化甲烷。
Zotero 插件