99038-25-2Relevant articles and documents
Rate-Limiting Step of Epoxidation Reaction of the Oxoiron(IV) Porphyrin π-Cation Radical Complex: Electron Transfer Coupled Bond Formation Mechanism
Fujii, Hiroshi,Hada, Masahiko,Ishimizu, Yuri,Ma, Zhifeng
, p. 17687 - 17698 (2021/12/01)
Epoxidation reactions catalyzed by high-valent metal-oxo species are key reactions in various biological and chemical processes. Because the redox potentials of alkenes are higher than those of most high-valent metal-oxo species, the electron transfer (ET
Reactivity studies on FeIII-(O22-)-Cu II compounds: Influence of the ligand architecture and copper ligand denticity
Chufan, Eduardo E.,Mondal, Biplab,Gandhi, Thirumanavelan,Kim, Eunsuk,Rubie, Nick D.,Moenne-Loccoz, Pierre,Karlin, Kenneth D.
, p. 6382 - 6394 (2008/10/09)
Heme-Cu/O2 adducts are of interest in the elucidation of the fundamental metal-O2 chemistry occurring in heme-Cu enzymes which effect reductive O-O cleavage of dioxygen to water. In this report, the chemistry of four heme-peroxo-copper [FeIII-(O2 2-)-CuII]+ complexes (1-4), varying in their ligand architecture, copper-ligand denticity, or both and thus their structures and physical properties are compared in their reactivity toward CO, PPh 3, acids, cobaltocene, and phenols. In 1 and 2, the copper(II) ligand is N4-tetradentate, and the peroxo unit is bound side-on to iron(III) and end-on to the copper(II). In contrast, 3 and 4 contain a N 3-tridentate copper(II) ligand, and the peroxo unit is bound side-on to both metal ions. CO displaces the peroxo ligand from 2-4 to form reduced CO-FeII and CO-CuI species. PPh3 reacts with 3 and 4 displacing the peroxide ligand from copper, forming (porphyrinate)FeIII-superoxide plus CuI-PPh3 species. Complex 2 does not react with PPh3, and surprisingly, 1 reacts neither with PPh3 nor CO, exhibiting remarkable stability toward these reagents. The behavior of 1 and 2 compared to that of 3 and 4 correlates with the different denticity of the copper ligand (tetra vs tridentate). Complexes 1-4 react with HCl releasing H2O2, demonstrating the basic character of the peroxide ligand. Cobaltocene causes the two-electron reduction of 1-4 giving the corresponding μ-oxo [Fe III-(O2-)-CuII]+ complexes, in contrast to the findings for other heme-peroxo-copper species of different design. With t-butyl-substituted phenols, no reaction occurs with 1-4. The results described here emphasize how ligand design and variations influence and control not only the structure and physical properties but also the reactivity patterns for heme-Cu/O2 adducts. Implications for future investigations of protonated heme/Cu-peroxo complexes, low-spin analogues, and ultimately O-O cleavage chemistry are discussed.
(F8TPP)FeII/O2 reactivity studies {F8TPP = tetrakis(2,6-difluorophenyl)porphyrinate(2-)}: Spectroscopic (UV-visible and NMR) and kinetic study of solvent-dependent (Fe/O2 = 1:1 or 2:1) reversible O2-reduction and ferryl formation
Ghiladi,Kretzer,Guzei,Rheingold,Neuhold,Hatwell,Zuberbuehler,Karlin
, p. 5754 - 5767 (2008/10/08)
In this report, we describe in detail the O2-binding chemistry of the metalloporphyrin (F8TPP)FeII (1). This complex was synthesized from aqueous dithionite reduction of (F8TPP)FeIII-Cl (X-ray structure reported: C55H36ClF8-FeN4O; a = 13.6517(2) A, b = 13.6475(2) A, c = 26.3896(4), α = 90°, β = 89.9776(4)°, γ = 90°; monoclinic, P2(1)/c, Z = 4). Complex 1 crystallizes from toluene/heptane solvent system as a bis(toluene) solvate, (F8TPP)FeII·(C7H8) 2, with ferrous ion in the porphyrin plane (C58H36F8FeN4; a = 20.9177(2) A, b = 11.7738(2) A, c = 19.3875(2), α = 90°, β = 108.6999(6)°, γ = 90°; monoclinic, C2/c, Z = 4; Fe-N4(av) = 2.002 A, N-Fe-N (all) = 90.0°). Close metal-arene contacts are also observed at 3.11-3.15 A. Upon oxygenation of 1 at 193 K in coordinating solvents, UV-visible and 2H and 19F NMR spectroscopies revealed the presence of a reversibly formed dioxygen adduct, formulated as the heme-superoxo complex (S)(F8TPP)FeIII-(O2-) (2) (S = solvent) [(i) tetrahydrofuran (THF) solvent: UV-visible, 416 (Soret), 536 nm; 2H NMR: δpyrrole 8.9 ppm; (ii) EtCN solvent: UV-visible, 414 (Soret), 536 nm; (iii) acetone solvent: UV-visible, 416 (Soret), 537 nm; 2H NMR: δpyrrole 8.9 ppm]. Dioxygen-uptake manometry (THF, 193 K) revealed an O2:1 oxygenation stoichiometry of 1.02:1, consistent with the heme-superoxo formulation of 2. Stopped-flow UV-visible spectrophotometry studies of the (F8TPP)FeII (1)/O2 reaction in EtCN and THF solvents were able to provide kinetic and thermodynamic insight into the reversible formation of 2 [(i) EtCN: ΔH° = -40 ± 5 kJ/mol; ΔS° = -105 ± 23 J/(K mol); k1 = (5.57 ± 0.04) × 103 M-1 s-1 (183 K); ΔH? = 38.6 ± 0.2 Jd/mol; ΔS? = 42 ± 1 J/(K mol); (ii) THF: ΔH° = -37.5 ± 0.4 kJ/mol; ΔS° = -109 ± 2 J/(K mol)}. The (F8TPP)FeII (1)/O2 reaction was also examined at reduced temperatures in noncoordinating solvents (toluene, CH2Cl2), where UV-visible and 2H and 19F NMR spectroscopies also revealed the presence of a reversibly formed adduct, formulated as the peroxo-bridged dinuclear complex [(F8TPP)FeIII]2-(O22-) (3) [CH2Cl2: UV-visible, 414 (Soret), 535 nm; 2H NMR, δpyrrole 17.5 ppm]. Dioxygen-uptake spectrophotometric titrations revealed a stoichiometry of 2 (F8TPP)FeII (1) per O2 upon full formation of 3. Addition of a nitrogenous base, 4-(dimethylamino)pyridine, to a cold solution of 3 in dichloromethane gave rapid formation of the iron(IV)-oxo ferryl species (DMAP)(F8TPP)FeIV=O (4), based upon UV-visible [417 (Soret), 541 nm] and 2H NMR (δpyrrole = 3.5 ppm) spectroscopic characterization. These detailed investigations into the O2-adducts and ferryl species formed from (F8TPP)FeII (1) may be potentially important for a full understanding of our ongoing heme-copper oxidase model studies, which employ 1 or similar tethered (i.e., covalently attached Cu-chelate) porphyrin analogues in heme/Cu heterobinuclear systems.
