Synthesis of an Iron(IV) Aqua–Oxido Complex Using Ozone as an Oxidant

Abstract

The iron(IV) oxido complex [(tmc)Fe=O(OTf)]OTf with the macrocyclic ligand 1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclo‐tetradecane (tmc) has been synthesized using ozone as an oxidant. By adding water to this compound the complex [(H2O)(tmc)Fe=O)](OTf)2 could be prepared. This complex is important in regard to a better understanding of the reactivity of FeIV oxido complexes. Mössbauer measurements using the solid compound showed an isomer shift of δ=0.19 mm s−1 and a quadrupole splitting ΔEQ=1.38 mm s−1, confirming the high‐valent FeIV state. DFT calculations were performed and led to an assignment of triplet spin multiplicity. Crystallographic characterization of [(H2O)(tmc)Fe=O)](OTf)2 as well as of starting materials [(tmc)Fe(CH3CN)](OTf)2 and [(tmc)Fe(OTf)]OTf together with previous results strongly suggest that [(H2O)(tmc)Fe=O)](OTf)2 was formed similar to the oxido–hydroxido tautomerism analogous to heme systems.

Syntheses and investigation of metal complexes with macrocyclic polythioether ligands

“…More recently we started to use ozone as an oxidant to trap an oxygen adduct complex, e.g. to obtain an iron( iv ) oxido complex with the ligand TMC, an approach based on earlier work by Wieghardt and co-workers as well as by Pestovsky et al 18 Furthermore, the oxygenation with ozone is well known for iron and manganese porphyrinoid complexes. 19 However, to the best of our knowledge, studies on the reactions of ozone and copper( i ) complexes to trap an “oxygen adduct” have not been reported so far.…”

Characterization of a Ferryl Flip in Electronically Tuned Nonheme Complexes. Consequences in Hydrogen Atom Transfer Reactivity

“…However, isomerization of the oxo ligand to a cis site has not been described yet for iron complexes. Previously described examples exclusively detail isomerizations towards trans sites on the basis of an oxo‐hydroxo tautomerism [36, 53–55] …”