Evaluating the Identity and Diiron Core Transformations of a (μ-Oxo)diiron(III) Complex Supported by Electron-Rich Tris(pyridyl-2-methyl)amine Ligands
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Lippard_Evaluating the Feb 20 2013.pdf
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Author(s)
Do, Loi Hung
Xue, Genqiang
Que, Lawrence
Lippard, Stephen J.
Date Issued
January 2012
Journal
Inorganic Chemistry
Publisher
American Chemical Society (ACS)
Citation
Do, Loi H., Genqiang Xue, Lawrence Que, and Stephen J. Lippard. “Evaluating the Identity and Diiron Core Transformations of a (μ-Oxo)diiron(III) Complex Supported by Electron-Rich Tris(pyridyl-2-methyl)amine Ligands.” Inorganic Chemistry 51, no. 4 (February 20, 2012): 2393-2402.
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Author's final manuscript
Abstract
The composition of a (μ-oxo)diiron(III) complex coordinated by tris[(3,5-dimethyl-4-methoxy)pyridyl-2-methyl]amine (R[subscript 3]TPA) ligands was investigated. Characterization using a variety of spectroscopic methods and X-ray crystallography indicated that the reaction of iron(III) perchlorate, sodium hydroxide, and R[subscript 3]TPA affords [Fe[subscript 2](μ-O)(μ-OH)(R[subscript 3]TPA)[subscript 2]](ClO[subscript 4])[subscript 3] (2) rather than the previously reported species [Fe[subscript 2](μ-O)(OH)(H[subscript 2]O)(R[subscript 3]TPA)[subscript 2]](ClO[subscript 4])[subscript 3] (1). Facile conversion of the (μ-oxo)(μ-hydroxo)diiron(III) core of 2 to the (μ-oxo)(hydroxo)(aqua)diiron(III) core of 1 occurs in the presence of water and at low temperature. When 2 is exposed to wet acetonitrile at room temperature, the CH[subscript 3]CN adduct is hydrolyzed to CH[subscript 3]COO[superscript –], which forms the compound [Fe[subscript 2](μ-O)(μ-CH[subscript 3]COO)(R[subscript 3]TPA)[subscript 2]](ClO[subscript 4])[subscript 3] (10). The identity of 10 was confirmed by comparison of its spectroscopic properties with those of an independently prepared sample. To evaluate whether or not 1 and 2 are capable of generating the diiron(IV) species [Fe[subscript 2](μ-O)(OH)(O)(R[subscript 3]TPA)[subscript 2]][superscript 3+] (4), which has previously been generated as a synthetic model for high-valent diiron protein oxygenated intermediates, studies were performed to investigate their reactivity with hydrogen peroxide. Because 2 reacts rapidly with hydrogen peroxide in CH[subscript 3]CN but not in CH[subscript 3]CN/H[subscript 2]O, conditions that favor conversion to 1, complex 1 is not a likely precursor to 4. Compound 4 also forms in the reaction of 2 with H[subscript 2]O[subscript 2] in solvents lacking a nitrile, suggesting that hydrolysis of CH[subscript 3]CN is not involved in the H[subscript 2]O[subscript 2] activation reaction. These findings shed light on the formation of several diiron complexes of electron-rich R[subscript 3]TPA ligands and elaborate on conditions required to generate synthetic models of diiron(IV) protein intermediates with this ligand framework.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1021/ic202379b
