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Crystallographic Evidence for a Sterically Induced Ferryl Tilt in a Non‐Heme Oxoiron(IV) Complex that Makes it a Better Oxidant
Author(s) -
Rasheed Waqas,
Draksharapu Apparao,
Banerjee Saikat,
Young Victor G.,
Fan Ruixi,
Guo Yisong,
Ozerov M.,
Nehrkorn Joscha,
Krzystek J.,
Telser Joshua,
Que Lawrence
Publication year - 2018
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201804836
Subject(s) - chemistry , steric effects , quinoline , electrophile , ligand (biochemistry) , heme , stereochemistry , pyridine , crystal structure , catalysis , crystallography , medicinal chemistry , receptor , enzyme , organic chemistry , biochemistry
Abstract Oxoiron(IV) units are often implicated as intermediates in the catalytic cycles of non‐heme iron oxygenases and oxidases. The most reactive synthetic analogues of these intermediates are supported by tetradentate tripodal ligands with N ‐methylbenzimidazole or quinoline donors, but their instability precludes structural characterization. Herein we report crystal structures of two [Fe IV (O)(L)] 2+ complexes supported by pentadentate ligands incorporating these heterocycles, which show longer average Fe–N distances than the complex with only pyridine donors. These longer distances correlate linearly with log k 2 ′ values for O‐ and H‐atom transfer rates, suggesting that weakening the ligand field increases the electrophilicity of the Fe=O center. The sterically bulkier quinoline donors are also found to tilt the Fe=O unit away from a linear N‐Fe=O arrangement by 10°.