Kinetics of (Porphyrin)manganese(<scp>III</scp>)‐Catalyzed Olefin Epoxidation with a Soluble Iodosylbenzene Derivative

Collman, James P.; Zeng, Li; Wang, Hong J. H.; Lei, Aiwen; Brauman, John I.

doi:10.1002/ejoc.200600079

Cited by 44 publications

(29 citation statements)

References 61 publications

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“…However, even for the H system the transition-state energy of TSA C H T U N G T R E N N U N G (4-5) is very close to that of TSA C H T U N G T R E N N U N G (2-3), and entropic effects disfavor TSA C H T U N G T R E N N U N G (4-5) with respect to TSA C H T U N G T R E N N U N G (2-3), because two species have been added to the system (ROOH and ethylene) in TSA C H T U N G T R E N N U N G (4-5) and only one (ROOH) in TSA C H T U N G T R E N N U N G (2-3) (see Supporting Information). From the experimental point of view, all previous kinetic studies yield results consistent with the rate-determining step being oxygen transfer to the olefin, [50][51][52] including a recent study on a cyclopentadienyl-substituted Mo VI catalyst, [CpMoO 2 -…”

supporting

confidence: 57%

A Computational Study of the Olefin Epoxidation Mechanism Catalyzed by Cyclopentadienyloxidomolybdenum(VI) Complexes

Comas‐Vives

Lledós

Poli

2010

Chemistry A European J

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A DFT analysis of the epoxidation of C(2)H(4) by H(2)O(2) and MeOOH (as models of tert-butylhydroperoxide, TBHP) catalyzed by [Cp*MoO(2)Cl] (1) in CHCl(3) and by [Cp*MoO(2)(H(2)O)](+) in water is presented (Cp*=pentamethylcyclopentadienyl). The calculations were performed both in the gas phase and in solution with the use of the conductor-like polarizable continuum model (CPCM). A low-energy pathway has been identified, which starts with the activation of ROOH (R=H or Me) to form a hydro/alkylperoxido derivative, [Cp*MoO(OH)(OOR)Cl] or [Cp*MoO(OH)(OOR)](+) with barriers of 24.9 (26.5) and 28.7 (29.2) kcal mol(-1) for H(2)O(2) (MeOOH), respectively, in solution. The latter barrier, however, is reduced to only 1.0 (1.6) kcal mol(-1) when one additional water molecule is explicitly included in the calculations. The hydro/alkylperoxido ligand in these intermediates is eta(2)-coordinated, with a significant interaction between the Mo center and the O(beta) atom. The subsequent step is a nucleophilic attack of the ethylene molecule on the activated O(alpha) atom, requiring 13.9 (17.8) and 16.1 (17.7) kcal mol(-1) in solution, respectively. The corresponding transformation, catalyzed by the peroxido complex [Cp*MoO(O(2))Cl] in CHCl(3), requires higher barriers for both steps (ROOH activation: 34.3 (35.2) kcal mol(-1); O atom transfer: 28.5 (30.3) kcal mol(-1)), which is attributed to both greater steric crowding and to the greater electron density on the metal atom.

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supporting

confidence: 57%

A Computational Study of the Olefin Epoxidation Mechanism Catalyzed by Cyclopentadienyloxidomolybdenum(VI) Complexes

Comas‐Vives

Lledós

Poli

2010

Chemistry A European J

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“…1b, compound 1) by introducing an intramolecular I-O bond to avoid the formation of polymeric structure. Later, Collman et al 51 used this kind of iodosylarene in kinetic investigations of olefin epoxidation, using manganese(III) porphyrin as the catalyst. Therefore, the soluble iodosylarene derivative enables us to observe intermediates by ultraviolet-vis spectroscopy and obtain kinetic data.…”

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confidence: 99%

Spectroscopic observation of iodosylarene metalloporphyrin adducts and manganese(V)-oxo porphyrin species in a cytochrome P450 analogue

Guo

Dong

et al. 2012

Nat Commun

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Different metalloporphyrin model compounds have been synthesized to study the mechanisms of cytochrome P450s with various terminal oxidants, and numerous intermediates have been reported. However, the detailed mechanism of the oxygen atom transfer from iodosylarene to the substrates remains unclear. Here we report the direct ultraviolet-visible spectroscopic observation of the soluble iodosylarene-manganese porphyrin adduct following catalytic oxidation using 2,4,6-tri-tert-butylphenol as the reductant. When the reductant is changed to cisstilbene, the rate-determining step also changes. Both the iodosylarene-manganese porphyrin adduct and [(porphyrin)Mn(V) ¼ O] species may be simultaneously observed. In the absence of reductant, the adduct of iodosylarene with sterically hindered [Mn(meso-tetrakis(2,6-dichlorophenyl)porphinato)Cl] is immediately formed, and smoothly converted into a highvalent [(porpyrinato)Mn ¼ O]. Electrospray ionization mass spectrometry analysis of the reaction further confirms the transformation between these species. This study provides an insight into the mechanism of oxygen transfer within the haem-containing enzymatic systems.

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“…6,15,28,39,50,51 After the reaction, the silicas were washed with a Et 2 NCS 2 Na solution to remove any advantageously bonded copper catalyst, then rinsed with sodium acetate solution to remove excess Et 2 NCS 2 Na.…”

Section: Resultsmentioning

confidence: 99%

Discrete Complexes Immobilized onto Click-SBA-15 Silica: Controllable Loadings and the Impact of Surface Coverage on Catalysis

2012

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Azidopropyl functionalized mesoporous silica SBA-15 were prepared with variable azide loadings of 0.03 – 0.7 mmol g−1 (ca. 2 – 50% of maximal surface coverage) through a direct synthesis, co-condensation approach. These materials are functionalized selectively with ethynylated organic moieties through the copper-catalyzed azide alkyne cycloaddition (CuAAC) or “click” reaction. Specific loading within a material can be regulated by either the azide loading or limiting the alkyne reagent relative to the azide loading. The immobilization of ferrocene, pyrene, tris(pyridylmethyl)amine (TPA), and iron porphyrin (FeTPP) demonstrates the robust nature and reproducibility of this two step synthetic attachment strategy. Loading-sensitive pyrene fluorescence correlates with a theoretically random. surface distribution, rather than a uniform one; full site-isolation of tethered moieties ca. 15 Å in length. occurs at loadings less than 0.02 mmol g−1. The effect of surface loading on reactivity is observed in oxygenation of SBA-15-[CuI(TPA)]. SBA-15-[MnII(TPA)]-catalyzed epoxidation exhibits a systematic dependence on surface loading. A comparison of homogeneous, site-isolated and site-dense complexes provides insight into catalyst speciation and ligand activity.

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Kinetics of (Porphyrin)manganese(III)‐Catalyzed Olefin Epoxidation with a Soluble Iodosylbenzene Derivative

Cited by 44 publications

References 61 publications

A Computational Study of the Olefin Epoxidation Mechanism Catalyzed by Cyclopentadienyloxidomolybdenum(VI) Complexes

A Computational Study of the Olefin Epoxidation Mechanism Catalyzed by Cyclopentadienyloxidomolybdenum(VI) Complexes

Spectroscopic observation of iodosylarene metalloporphyrin adducts and manganese(V)-oxo porphyrin species in a cytochrome P450 analogue

Discrete Complexes Immobilized onto Click-SBA-15 Silica: Controllable Loadings and the Impact of Surface Coverage on Catalysis

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