Double act: The diiron(II) complex [Fe2(6‐HPA)(O)(OH2)2](ClO4)4 (1) catalyzes alkene epoxidation with H2O2 via a peroxodiiron complex. Detailed isotope‐labeling experiments with μ‐18O‐1 reveal incorporation of both oxo‐ and peroxo‐derived oxygen atoms into the epoxide reaction product (see scheme; 6‐HPA=1,2‐bis[2‐{bis(2‐pyridylmethyl)aminomethyl}‐6‐pyridyl]ethane).

The mechanism of O 2 -activation and oxygenation of CH 4 to CH 3 OH by soluble methane monooxygenase hydroxylase (sM-MOH) is of great current interest. 2 The diiron(II) center of sMMOH binds dioxygen to form a µ-peroxodiiron(III) intermediate P 3 via two transient intermediates O and P*, 4 and P is converted to an active intermediate Q. 5 P and Q have been studied spectroscopically 3-5 and followed by model studies. 6,7 A radicalrebound mechanism of the C-H oxygenation by Q has been proposed on the basis of product analysis and the kinetic isotope effect. 8 These results have been supported by DFT calculations. 9

Zweispänner: Der Dieisen(II)‐Komplex [Fe2(6‐HPA)(O)(OH2)2](ClO4)4 (1) katalysiert die Alkenepoxidierung mit H2O2 über einen Peroxodieisenkomplex. Ausführliche Isotopenmarkierungsexperimente mit μ‐18O‐1 ergaben, dass sowohl aus dem Oxo‐ als auch aus dem Peroxoliganden stammende Sauerstoffatome in das Epoxidprodukt eingebaut werden (siehe Schema). 6‐HPA=1,2‐Bis[2‐{bis(2‐pyridylmethyl)aminomethyl}‐6‐pyridyl]ethan.