Photochemical generation of a highly reactive iron-oxo intermediate. A true iron(V)-oxo species?
Photochemical generation of a highly reactive iron-oxo intermediate. A true iron(V)-oxo species?
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DOI：
10.1021/ja0542439
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发表时间：
2005-10-12
影响因子：
15
通讯作者：
Newcomb, M
中科院分区：
文献类型：
--
作者：
Harischandra, DN;Zhang, R;Newcomb, M
从相应的氯化物制备的5，10，15-tris(pentafluorophenyl)corrole−iron(IV)氯酸盐或硝酸盐的激光闪光光解产生了高活性的铁−氧物种，根据其UV−可见光谱和高反应活性以及类似于相关锰物种的光化学配体裂解反应，被鉴定为铁(V)−氧物种。在与顺-环辛烯的制备反应中，该瞬变被证明是一个氧转移试剂。环辛烯和乙苯在室温下氧化反应的典型速率常数分别为k=5900M-1s-1和k=570M-1s-1。对于Fe(IV)−氧自由基阳离子，新的瞬变与典型有机还原剂的活性比预期高6个数量级以上，比类似正电荷铁(IV)−氧基卟啉自由基阳离子的活性高100倍。配体Fe(V)−氧物种到Fe(IV)−氧自由基阳离子的慢电子转移异构化在实验室和自然界的卟啉−铁催化剂的反应中可能是重要的。
Laser flash photolysis of 5,10,15-tris(pentafluorophenyl)corrole−iron(IV) chlorate or nitrate, prepared from the corresponding chloride, gave a highly reactive iron−oxo transient identified as an iron(V)−oxo species on the basis of its UV−visible spectrum and high reactivity as well as by analogy to photochemical ligand cleavage reactions of related manganese species. The transient was shown to be an oxo transfer agent in a preparative reaction withcis-cyclooctene. Representative rate constants for oxidation reactions by the new transient at ambient temperature werek= 5900 M-1s-1for cyclooctene andk= 570 M-1s-1for ethylbenzene. The new transient is more than 6 orders of magnitude more reactive with typical organic reductants than expected for an iron(IV)−oxo corrole radical cation and 100 times more reactive than an analogous positively charged iron(IV)−oxo porphyrin radical cation. Slow electron transfer isomerization of ligand iron(V)−oxo species to iron(IV)−oxo ligand radical cations might be important in reactions of porphyrin−iron catalysts in the laboratory and in nature.