The O 2 -reaction chemistry of 1:1 mixtures of (F 8 )Fe II (1; F 8 = tetrakis(2,6-diflurorophenyl)porphyrinate) and [(L Me 2 N )Cu I ] + (2; L Me 2 N = N , N -bis{2-[2-( N ′, N ′-4-dimethylamino)pyridyl]ethyl}methylamine) is described, to model aspects of the chemistry occurring in cytochrome c oxidase. Spectroscopic investigations, along with stopped-flow kinetics, reveal that low-temperature oxygenation of 1/2 leads to rapid formation of a heme-superoxo species (F 8 )Fe III -(O \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{2}^{-}}}\end{equation*}\end{document} ) (3), whether or not 2 is present. Complex 3 subsequently reacts with 2 to form [(F 8 )Fe III –(O \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} \begin{equation*}{\mathrm{_{2}^{2-}}}\end{equation*}\end{document} )–Cu II (L Me 2 N )] + (4), which thermally converts to [(F 8 )Fe III –(O)–Cu II (L Me 2 N )] + (5), which has an unusually bent (Fe–O–Cu) bond moiety. Tridentate chelation, compared with tetradentate, is shown to dramatically lower the ν(O–O) values observed in 4 and give rise to the novel structural features in 5.
Steady state and laser flash photolysis studies of the heme/non-heme μ-oxo diiron complex [(6L)FeIIIOFeIIICl]+ (1) have been undertaken. The anaerobic photolysis of benzene solutions of 1 did not result in the buildup of any photoproduct. However, the addition of excess triphenylphosphine resulted in the quantitative photoreduction of 1 to [(6L)FeII···FeIICl]+ (2), with concomitant production by oxo-transfer of 1 equiv of triphenylphosphine oxide. Under aerobic conditions and excess triphenylphosphine, the reaction produces multiple turnovers (∼28) before the diiron complex is degraded. The anaerobic photolysis of tetrahydrofuran (THF) or toluene solutions of 1 likewise results in the buildup of 2. The oxidation products from these reactions included γ-butyrolactone (∼15%) for the reaction in THF and benzaldehyde (∼23%) from the reaction in toluene. In either case, the O-atom which is incorporated into the carbonyl product is derived from dioxygen present under workup or under aerobic photolysis conditions. Transient absorption measurements of low-temperature THF solutions of 1 revealed the presence of an (P)FeII-like {P = tetraaryl porphyrinate dianion} species suggesting that the reactive species is a formal (heme)FeII/FeIVO(non-heme) pair. The non-heme FeIVO is thus most likely responsible for CH bond cleavage and subsequent radical chemistry. The photolysis of 1 in chlorobenzene or 1,2-dichlorobenzene resulted in C−Cl cleavage reactions and the formation of {[(6L)FeIIICl···FeIIICl]2O}2+ (3), with chloride ligands that are derived from solvent dehalogenation chemistry. The resulting organic products are biphenyl trichlorides or biphenyl monochlorides, derived from dichlorobenzene and chlorobenzene, respectively. Similarly, product 3 is obtained by the photolysis of benzene−benzyl chloride solutions of 1; the organic product is benzaldehyde (∼70%). A brief discussion of the dehalogenation chemistry, along with relevant environmental perspectives, is included.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Single wavelength excitation (λex = 355 or 532 nm) of low-temperature stabilized (198 K) synthetic heme−dioxygen and heme−dioxygen/M complexes, where M = copper or iron in a non-heme environment, results in the dissociation of dioxygen as indicated by the generation of the ferrous heme (Soret band, 427 nm) and the bleaching of the ferric-superoxide (FeIII(O2-)) 410-nm Soret band in the transient absorption difference spectrum. Dioxygen rebinds to the four heme complexes studied with comparable rate constants (∼6−9 × 105 M-1 s-1). However, the quantum yield for complete dissociation of O2 from our simplest heme−O2 complex (F8)FeIII(O2-) (φ = 0.60) is higher than the other complexes measured (φ = ∼0.2−0.3) as well as that for oxy-myoglobin (φ = 0.3).
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Reaction of FvW(2)(H)(2)(CO)(6) with 2/8S(8) in THF results in rapid and quantitative formation of FvW(2)(SH)(2)(CO)(6). The crystal structure of this complex is reported and shows that the two tungsten-hydrosulfide groups are on opposite faces of the fulvalene ligand in an anti configuration. Nevertheless, treatment of FvW(2)(SH)(2)(CO)(6) (1) with PhN[double bond]NPh produces FvW(2)(mu-S(2))(CO)(6) (2) and Ph(H)NN(H)Ph. The crystal structure of the bridging disulfide, which cocrystallizes with 1 in a 2:1 ratio, is also described. Exposure of 2 equiv of *CrCp*(CO)(3) to 1 effects similar H atom transfers yielding 2 HCrCp*(CO)(3) and 2. Attempts to obtain crystals of the latter from solutions derived from this reaction mixture furnished a third product, FvW(2)(mu-S)(CO)(6) (3), which was analyzed crystallographically. The enthalpy of sulfur atom insertion into FvW(2)(H)(2)(CO)(6), yielding 1, has been measured by solution calorimetry.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
As a first generation model for the reactive reduced active-site form of bacterial nitric oxide reductase, a heme/non-heme diiron(II) complex [(6L)FeII···FeII−(Cl)]+ (2) {where 6L = partially fluorinated tetraphenylporphyrin with a tethered tetradentate TMPA chelate; TMPA = tris(2-pyridyl)amine} was generated by reduction of the corresponding μ-oxo diferric compound [(6L)FeIII−O−FeIII−Cl]+ (1). Coordination chemistry models for reactions of reduced NOR with O2, CO, and NO were also developed. With O2 and CO, adducts are formed, [(6L)FeIII(O2-)(thf)···FeII−Cl]B(C6F5)4 (2a·O2) {λmax 418 (Soret), 536 nm; νO-O = 1176 cm-1, νFe-O = 574 cm-1 and [(6L)FeII(CO)(thf)FeII−Cl]B(C6F5)4 (2a·CO) {νCO 1969 cm-1}, respectively. Reaction of purified nitric oxide with 2 leads to the dinitrosyl complex [(6L)Fe(NO)Fe(NO)−Cl]B(C6F5)4 (2a·(NO)2) with νNO absorptions at 1798 cm-1 (non-heme Fe−NO) and 1689 cm-1 (heme−NO).
