Catalytically active μ-oxodiiron(IV) oxidants from iron(III) and dioxygen
Catalytically active μ-oxodiiron(IV) oxidants from iron(III) and dioxygen
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DOI：
10.1021/ja0460458
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发表时间：
2005-03-02
影响因子：
15
通讯作者：
Collins, TJ
中科院分区：
文献类型：
--
作者：
Ghosh, A;de Oliveira, FT;Collins, TJ
本文描述了铁-Ⅲ络合物与氧-2反应生成稳定的催化活性的二铁(IV)-钼氧化合物。在CH2Cl2或其他弱配位溶剂中，橙色五配位Fe-III-TAML与轴向水配体([PPh_4]_1-H_2O，3，3，6，6，9，9-hexamethyl-3，4，8，9-tetrahydro-1H-1，4，8，11-benzotetraazacyclotridecine-2，5，7，10(6H，11H)-tetraone)衍生的四胺基大环Fe-III物种)形成的配合物与O-2快速反应，高产率地生成黑色的钼氧桥联二铁(IV)配合物2。通过X-射线结晶学(2例)、微量分析数据、质谱学、UV/Vis、穆斯堡尔谱和核磁共振氢谱对化合物2进行了表征。穆斯堡尔谱数据表明，反磁的Fe-O-Fe单元含有反铁磁耦合的S=1个Fe-IV位，观察到了反磁的H-1核磁共振谱。UV/Vis和GC-MS证实了PPh3被2氧化为OPPh3。O-18(2)和(H2O)-O-18的标记实验表明，2的桥氧原子来源于O-2。配合物2催化将苯甲醇选择性氧化成相应的醛，并快速漂白有机染料，如在MeCN-H2O混合物中的橙色II；反应性证据表明，不涉及自由基自氧化。这项工作突出了绿色氧化技术的发展前景，因为O-2是一种丰富、清洁、廉价的氧化剂。
The reaction between an Fe-III complex and O-2 to afford a stable catalytically active diiron(IV)-mu-oxo compound is described. Phosphonium salts of orange five-coordinated Fe-III-TAML complexes with an axial aqua ligand ([PPh4]1-H2O, tetraamidato macrocyclic Fe-III species derived from 3,3,6,6,9,9-hexamethyl-3,4,8,9-tetrahydro-1H-1,4,8,11-benzotetraazacyclotridecine-2,5,7,10(6H,11H)-tetraone) react rapidly with O-2 in CH2Cl2 or other weakly coordinating solvents to produce black mu-oxo-bridged diiron(IV) complexes, 2, in high yields. Complexes 2 have been characterized by X-ray crystallography (2 cases), microanalytical data, mass spectrometry, UV/Vis, Mossbauer, and H-1 NMR spectroscopies. Mossbauer data show that the diamagnetic Fe-O-Fe unit contains antiferromagnetically coupled S = 1 Fe-IV sites; diamagnetic H-1 NMR spectra are observed. The oxidation of PPh3 to OPPh3 by 2 was confirmed by UV/Vis and GC-MS. Labeling experiments with O-18(2) and (H2O)-O-18 established that the bridging oxygen atom of 2 derives from O-2. Complexes 2 catalyze the selective oxidation of benzylic alcohols into the corresponding aldehydes and bleach rapidly organic dyes, such as Orange II in MeCN-H2O mixtures; reactivity evidence suggests that free radical autoxidation is not involved. This work highlights a promising development for the advancement of green oxidation technology, as O-2 is an abundant, clean, and inexpensive oxidizing agent.