A Structural and Functional Model for the 1‐Aminocyclopropane‐1‐carboxylic Acid Oxidase

The hitherto most realistic low‐molecular‐weight analogue for the 1‐aminocyclopropane‐1‐carboxylic acid oxidase (ACCO) is reported. The ACCOs 2‐His‐1‐carboxylate iron(II) active site was mimicked by a TpFe moiety, to which the natural substrate ACC could be bound. The resulting complex [Tp Me,Ph FeACC] ( 1 ), according to X‐ray diffraction analysis performed for the nickel analogue, represents an excellent structural model, featuring ACC coordinated in a bidentate fashion—as proposed for the enzymatic substrate complex—as well as a vacant coordination site that forms the basis for the first successful replication also of the ACCO function: 1 is the first known ACC complex that reacts with O 2 to produce ethylene. As a FeOOH species had been suggested as intermediate in the catalytic cycle, H 2 O 2 was tested as the oxidant, too, and indeed evolution of ethylene proceeded even more rapidly to give 65 % yield.