Enhancing reactivity: A common feature of non-heme iron enzymes is the presence of carboxylate groups. An axial carboxylate group has been introduced trans to the oxo group of a non-heme oxoiron(iv) complex (see scheme). The coordination of carboxylate destabilizes the FeIV[DOUBLE BOND]O unit and activates it towards reaction with dihydroanthracene.