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Facile Conversion of syn ‐[Fe IV (O)(TMC)] 2+ into the anti Isomer via Meunier's Oxo–Hydroxo Tautomerism Mechanism
Author(s) -
Prakash Jai,
Sheng Yuan,
Draksharapu Apparao,
Klein Johannes E. M. N.,
Cramer Christopher J.,
Que Lawrence
Publication year - 2019
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201811454
Subject(s) - isomerization , chemistry , tautomer , ligand (biochemistry) , stereochemistry , nuclear magnetic resonance spectroscopy , molecule , crystallography , catalysis , organic chemistry , biochemistry , receptor
The syn and anti isomers of [Fe IV (O)(TMC)] 2+ (TMC=tetramethylcyclam) represent the first isolated pair of synthetic non‐heme oxoiron(IV) complexes with identical ligand topology, differing only in the position of the oxo unit bound to the iron center. Both isomers have previously been characterized. Reported here is that the syn isomer [Fe IV (O syn )(TMC)(NCMe)] 2+ ( 2 ) converts into its anti form [Fe IV (O anti )(TMC)(NCMe)] 2+ ( 1 ) in MeCN, an isomerization facilitated by water and monitored most readily by 1 H NMR and Raman spectroscopy. Indeed, when H 2 18 O is introduced to 2 , the nascent 1 becomes 18 O‐labeled. These results provide compelling evidence for a mechanism involving direct binding of a water molecule trans to the oxo atom in 2 with subsequent oxo–hydroxo tautomerism for its incorporation as the oxo atom of 1 . The nonplanar nature of the TMC supporting ligand makes this isomerization an irreversible transformation, unlike for their planar heme counterparts.