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Copper(II) complexes of the potentially tripodal N,N,O ligand 3,3‐bis(1‐methylimidazol‐2‐yl)propionate (L1) and its conjugate acid HL1 have been synthesised and structurally and spectroscopically characterised. The reaction of equimolar amounts of ligand and CuIIresulted in the complexes [Cu(L1)]n(X)n(X=OTf−, PF6−; n=1,2), for which a new bridging coordination mode of L1 is inferred. Although these complexes showed moderate catecholase activity in the oxidation of 3,5‐di‐tert‐butylcatechol, surprising reactivity with the pseudo‐substrate tetrachlorocatechol was observed. A chloranilato‐bridged dinuclear CuIIcomplex was isolated from the reaction of [Cu(L1)]n(PF6)nwith tetrachlorocatechol. This stoichiometric oxidative double dehalogenation of tetrachlorocatechol to chloranilic acid by a biomimetic copper(II) complex is unprecedented. The crystal structure of the product, [Cu2(ca)Cl2(HL1)2], shows a bridging bis‐bidentate chloranilato (ca) ligand and ligand L1 coordinated as its conjugate acid (HL1) in a tridentate fashion. Magnetic susceptibility studies revealed weak antiferromagnetic coupling (J=−35 cm−1) between the two copper centres in the dinuclear complex. Dissolution of the green complex [Cu2(ca)Cl2(HL1)2] resulted in the formation of new pink‐purple mononuclear compound [Cu(ca)(HL1)(H2O)], the crystal structure of which was determined. It showed a terminal bidentate chloranilato ligand and N,N‐bidentate coordination of ligand HL1, which illustrates the flexible coordination chemistry of ligand L1.

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 PrL1were determined and two different coordination modes of the ligand were observed. In [FeII(PrL1)2](BPh4)2(3) the ligand is facially coordinated to the metal with an N,N,O donor set, whereas in [FeII(PrL1)2(MeOH)2](OTf)2(4) a bidentate N,N binding mode is found. In 4, the solvent molecules are in a cisarrangement with respect to each other. Complex 4is 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 [FeII(PrL1)2](OTf)2(2) and [FeII(PrL1)2](BPh4)2(3) were tested in olefin oxidation reactions with H2O2as the terminal oxidant. Whereas 2was an active catalyst and both epoxide and cis‐dihydroxylation products were observed, 3showed negligible activity under the same conditions, illustrating the importance of the anion in the reaction.