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Disproportionation Equilibrium of a μ ‐Oxodiiron(III) Complex Giving Rise to C−H Activation Reactivity: Structural Snapshot of a Unique Oxoiron(IV) Adduct
Author(s) -
Cordes née Kupper Claudia,
Morganti Massimiliano,
Klawitter Iris,
Schremmer Claudia,
Dechert Sebastian,
Meyer Franc
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.201900683
Subject(s) - disproportionation , chemistry , autoxidation , adduct , reactivity (psychology) , catalysis , equilibrium constant , monomer , medicinal chemistry , stereochemistry , photochemistry , organic chemistry , medicine , polymer , alternative medicine , pathology
μ‐Oxodiiron(III) species are air‐stable and unreactive products of autoxidation processes of monomeric heme and non‐heme iron(II) complexes. Now, the organometallic [(L NHC )Fe III ‐(μ‐O)‐Fe III (L NHC )] 4+ complex 1 (L NHC is a macrocyclic tetracarbene) is shown to be reactive in C−H activation without addition of further oxidants. Studying the oxidation of dihydroanthracene, it was found that 1 thermally disproportionates in MeCN solution into its oxoiron(IV) ( 2 ) and iron(II) components; the former is the active species in the observed oxidation processes. Possible cleavage scenarios for 1 are shown by scrambling experiments and structural characterization of an unprecedented adduct of 1 and oxoiron(IV) complex 2 . Kinetic analysis gave an equilibrium constant for the disproportionation of 1 , which is very small ( K eq =7.5±2.5×10 −8 m ). Increasing K eq might by a useful strategy for circumventing the formation of dead‐end μ‐oxodiiron(III) products during Fe‐based homogeneous oxidation catalysis.