Mechanistic Studies of the Oxidative N-Dealkylation of a Substrate Tethered to Carboxylate-Bridged Diiron(II) Complexes, [Fe2(<img src="http://pubs.acs.org/images/entities/mgr.gif" b
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- 作者：Sungho Yoon and Stephen J. Lippard
- 刊名：Inorganic Chemistry
- 出版年：2006
- 出版时间：July 10, 2006
- 年：2006
- 卷：45
- 期：14
- 页码：5438 - 5446
- 全文大小：300K
- 年卷期：v.45,no.14(July 10, 2006)
- ISSN：1520-510X
文摘
Carboxylate-bridged diiron(II) centers activate dioxygen for the selective oxidation of hydrocarbon substrates inbacterial multicomponent monooxygenases. Synthetic analogues of these systems exist in which substrate fragmentstethered to the diiron(II) core through attachment to an N-donor ligand are oxidized by transient species that arisefollowing the introduction of O2 into the system. The present study describes the results of experiments designedto probe mechanistic details of these oxidative N-dealkylation reactions. A series of diiron(II) complexes with ligandsN,N-(4-R-Bn)Bnen, where en is ethylenediamine, Bn is benzyl, and R-Bn is benzyl with a para-directing group R= Cl, F, CH3, t-Bu, or OCH3, were prepared. A Hammett plot of the oxygenation product distributions of thesecomplexes, determined by gas chromatographic analysis, reveals a small positive slope of 
images/gifchars/rho.gif" BORDER=0 > = +0.48. Kineticisotope effect (KIEintra) values for oxygenation of [Fe2(images/entities/mgr.gif">-O2CArTol)2(O2CArTol)2(N,N-(C6H5CDH)2en)2] and[Fe2(images/entities/mgr.gif">-O2CArTol)2(O2CArTol)2(N,N-(C6H5CD2)(C6H5CH2)en)2] are 1.3(1) and 2.2(2) at 23 images/entities/deg.gif">C, respectively. The positiveslope images/gifchars/rho.gif" BORDER=0 > and low KIEintra values are consistent with a mechanism involving one-electron transfer from the danglingnitrogen atom in N,N-Bn2en to a transient electrophilic diiron intermediate, followed by proton transfer andrearrangement to eliminate benzaldehyde.