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

• Published in: Angewandte Chemie International Edition Vol. 57; no. 19; pp. 5355 - 5358
• Main Authors: Schaub, Stefan, Miska, Andreas, Becker, Jonathan, Zahn, Stefan, Mollenhauer, Doreen, Sakshath, Sadashivaiah, Schünemann, Volker, Schindler, Siegfried
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 04.05.2018
• Edition: International ed. in English
• Subjects: bioinorganic chemistry; Crystallography; Heme; Iron; Mossbauer spectroscopy; Mössbauer spectroscopy; non-heme iron complexes; Ozone; Quadrupoles; Tautomerism; Tetradecane; tetramethylcyclam; ozone; Mössbauer spectroscopy; bioinorganic chemistry; non-heme iron complexes; tetramethylcyclam
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201800475

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. Water does not always hurt: The iron(IV) oxido complex [(H2O)(tmc)Fe=O)](triflate)2 (1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane=tmc) has been synthesized and structurally characterized. This complex is quite unusual in regard to a coordinated water molecule as an additional axial ligand.