Biomimetic High-Valent Non-Heme Iron Oxidants for the cis-Dihydroxylation and Epoxidation of OlefinsFinancial support by the German Science Foundation (DFG) and an Alexander von Humboldt fellowship to G.R. are gratefully acknowledged

High-valent iron oxidants are known to be the catalytically active species in heme enzymes, and the last decade has seen similar developments in non-heme-iron biomimetics and biochemistry. 2] Extensive reactivity studies, structural, spectroscopic, and computational work have established {FeOOH} and {Fe=O} as relevant intermediates in catalytic oxygenation processes. The species {Fe=O} has also been trapped, characterized, and found to be active in oxygen transfer, and discrete {Fe} species have been spectroscopically characterized. TauD, an a-ketogluterate-dependent enzyme, is a well-characterized non-heme iron enzyme and has a high-spin (S= 2) center in its active form. The aqua ion is the only other known high-spin ferryl complex. 8] All biomimetic ferryl complexes characterized to date have intermediate-spin (S= 1) electronic configuration. Herein we present experimental data of the iron-catalyzed oxidation of cyclooctene by H2O2 with the tetradentate bispidine ligand L (Scheme 1a). The data indicate that unprecedented Fe