Abstract
The Rieske dioxygenases are a group of non‐heme iron enzymes, which catalyze the stereospecific cis‐dihydroxylation of its substrates. Herein, we report the iron(II) coordination chemistry of the ligands 3,3‐bis(1‐methylimidazol‐2‐yl)propionate (L1) and its neutral propyl ester analogue propyl 3,3‐bis(1‐methylimidazol‐2‐yl)propionate (PrL1). The molecular structures of two iron(II) complexes with PrL1 were determined and two different coordination modes of the ligand were observed. In Fe^II^(PrL1)~2~~2~ (3) the ligand is facially coordinated to the metal with an N,N,O donor set, whereas in Fe^II^(PrL1)~2~(MeOH)~2~~2~ (4) a bidentate N,N binding mode is found. In 4, the solvent molecules are in a cis arrangement with respect to each other. Complex 4 is a close structural mimic of the crystallographically characterized non‐heme iron(II) enzyme apocarotenoid‐15–15′‐oxygenase (APO). The mechanistic features of APO are thought to be similar to those of the Rieske oxygenases, the original inspiration for this work. The non‐heme iron complexes Fe^II^(PrL1)~2~~2~ (2) and Fe^II^(PrL1)~2~~2~ (3) were tested in olefin oxidation reactions with H~2~O~2~ as the terminal oxidant. Whereas 2 was an active catalyst and both epoxide and cis‐dihydroxylation products were observed, 3 showed negligible activity under the same conditions, illustrating the importance of the anion in the reaction.