Hydrogen Atom Abstraction by High-Valent Fe(OH) versus Mn(OH) Porphyrinoid Complexes: Mechanistic Insights from Experimental and Computational Studies
作者:Jan Paulo T. Zaragoza、Daniel C. Cummins、M. Qadri E. Mubarak、Maxime A. Siegler、Sam P. de Visser、David P. Goldberg
DOI:10.1021/acs.inorgchem.9b02923
日期:2019.12.16
through a concerted HAT mechanism, based on mechanistic analyses that include a KIE = 2.9(1) and DFT calculations. Comparison of the HAT reactivity of 1 to the analogous Mn complex, MnIV(OH)(ttppc), where only the central metal ion is different, indicates a faster HAT reaction and a steeper Hammett slope for 1. The O-H bond dissociation energy (BDE) of the MIII(HO-H) complexes were estimated from a kinetic
高价金属氢氧化物已被认为是血红素单加氧酶(例如细胞色素P450)催化的羟基化化学中的关键中间体。但是,在某些类型的P450中,观察到了典型的氧回弹路径的分叉,其中FeIV(OH)(卟啉)物种进行净氢原子转移反应以形成烯烃代谢物。在这项工作中,我们研究了FeIV(OH)(ttppc)(1)的氢原子转移(HAT)反应性,ttppc = 5,10,15-tris(2,4,6-三苯基)-苯甲酸酯对取代苯酚衍生物。氢氧化铁络合物1与一系列对位取代的2,6-二叔丁基苯酚衍生物(4-X-2,6-DTBP; X = OMe,Me,Et,H,Ac)反应,阶速率常数k2 = 3.6(1)-1.21(3)×104 M-1 s-1并产生线性Hammett和Marcus图相关性。结论是,基于包括KIE = 2.9(1)和DFT计算在内的机理分析,OH裂解的速率决定步骤是通过协调的HAT机理进行的。将1与类似的Mn配