Formation of an Aqueous Oxoiron(IV) Complex at pH 2–6 from a Nonheme Iron(II) Complex and H₂O₂

Abiotic methanogenesis from organosulphur compounds under ambient conditions

“…An alternative oxidant in aqueous Fe 2 þ /H 2 O 2 systems is [Fe IV ¼ O] 2 þ , and this ferryl species is known from nonhaeme iron enzymes and corresponding biomimetic oxidation catalysis 24,32 to be a powerful oxidant in aqueous solution [33][34][35][36] . Bispidine-type ligands have been shown to efficiently support the ferryl centre for oxidation catalysis.…”

Optimization of the Efficiency of Oxidation Catalysts Based on Iron Bispidine Complexes

“…Due to the availability of a wide variety of easy to prepare tetra-and pentadentate bispidine ligands (2,4-and 3-or 7-substituted 3,7-diazabicyclo[3.3.1]nonane; see Scheme 1 for the pentadentate 2,4,7-substituted bispidines L 1 -L 3 discussed in this communication) and based on their rich coordination chemistry, [8] their oxygen activation performance with copper, [9][10][11][12] cobalt, [13] vanadium, [14] ruthenium, [15,16] and iron [17][18][19][20][21] systems have been studied in detail. The iron systems in particular have been shown to be efficient oxygenation catalysts, and the iron chemistry of the L 1 -based pentadentate as well as the corresponding 2,4-substituted tetradentate bispidine ligands have indeed been shown to have, among the corresponding families of iron complexes, the highest Fe IV/III reduction potentials and the highest efficiencies in a range of C-H activation and oxygen-transfer reactions.…”

Iron-catalysed oxidation and halogenation of organic matter in nature

“…With bispidine-type ligands, the formation of ferryl complexes has been confirmed in some detail (see also Fig. 3), [57,88,101,119] and the mechanism of olefin epoxidation and dihydroxylation has been studied, both experimentally and by quantum-chemical methods. [120,121] Careful product analyses, including 18 Fig.…”

“…3). [88] Also of importance are reports on the halogenation of unactivated substrates with ferryl model systems. [89,90] It needs to be pointed out that non-heme iron enzymes generally activate dioxygen and that in most of the model reactions discussed here, the ferryl species are obtained from the Fe II precursors by oxygen atom transfer, electron transfer or oxidation with H 2 O 2 .…”

“…under Fenton-type conditions usually assumed in soils, water and aerosols -and therefore, they obviously play an important role in various environmental compartments. However, OH radicals are also produced in Fe II /H 2 O 2 systems and there is no doubt either that [57] ) with H 2 O 2 in water (0 8C, citrate buffer, pH 5.4; the dotted line is the electronic spectrum of the ferric complex, the dark line corresponds to the ferryl complex, developed within 80 s), [88] adapted from Comba. [ [68,69] these are also of importance in the oxidation of organic matter.…”