115775-87-6Relevant articles and documents
Mechanistic insights into hydride-transfer and electron-transfer reactions by a manganese(IV)-oxo porphyrin complex
Fukuzumi, Shunichi,Fujioka, Naofumi,Kotani, Hiroaki,Ohkubo, Kei,Lee, Yong-Min,Nam, Wonwoo
, p. 17127 - 17134 (2009)
Hydride transfer from dihydronicotinamide adenine dinucleotide (NADH) analogs to a manganese(IV)-oxo porphyrin complex, (TMP)MnIV(O) [TMP = 5,10,15,20-tetrakis(2,4,6-trimethylphenyl) porphyrin], occurs via disproportionation of (TMP)MnIV(O) to [(TMP)MnIII] + and [(TMP)MnV(O)]+ that acts as the actual hydride acceptor. In contrast, electron transfer from ferrocene derivatives to (TMP)MnIV(O) occurs directly to afford ferricenium ions and (TMP)MnIII(OH) products. The disproportionation rate constant of (TMP)MnIV(O) was determined by the dependence of the observed second-order rate constants on concentrations of NADH analogs to be (8.0 ± 0.6) × 106 M-1 s-1 in acetonitrile at 298 K. The disproportionation rate constant of (TMP)Mn IV(O) in hydride-transfer reactions increases linearly with increasing acid concentration, whereas the rate constant of electron transfer from ferrocene to (TMP)MnIV(O) remains constant irrespective of the acid concentration. The rate constants of electron transfer from a series of ferrocene derivatives to (TMP)MnIV(O) were evaluated in light of the Marcus theory of electron transfer to determine the reorganization energy of electron transfer by the (TMP)MnIV(O) complex.
The Kinetics for the Reaction of Hypochlorite with a Manganese(III) Porphyrin and Subsequent Epoxidation of Alkenes in a Homogeneous Solution
Lee, Robert W.,Nakagaki, Paul C.,Bruice, Thomas C.
, p. 1368 - 1372 (1989)
The reaction of (5,10,15,20-tetrakis(2,4,6-trimethylphenyl)porphinato)manganese(II) chloride with hypochlorite has been investigated.The reactions were studied in a wet-dichloromethane solution prepared by mixing, on the stopped-flow bench, solutions (A) containing (Me12TPP)Mn(III)(Cl) + 4'-imidazol-1-ylacetophenone (NAcPhIm) + alkene and those (B) containing ClO(1-) + benzyldimethyltetradecylammonium chloride (PTC).The time courses of the reactions were followed by conventional stopped-flow and rapid-scan stopped-flow spectrophotometry bymonitoring the disappearance of (Me12TPP)Mn(III)(Cl) (λmax=480 nm, ε=1.05*1E5 M-1 cm-1) and the appearance of (Me12TPP)Mn(IV)(O) and (Me12TPP)Mn(V)(O).Simulations of the kinetic results were carried out according to the reactions of Scheme I by the fitting of the time course for (Me12TPP)Mn(III)(Cl) disappearance and the yields of epoxide products.The rate constant for ClO(1-) + (Me12TPP)Mn(III)(Cl) --> Cl(1-) + (Me12TPP)Mn(V)(O) was determined as k1=(3.8+/-1.8)*1E5 M-1 s-1.The rate constant for the comproportionation reaction of (Me12TPP)Mn(III)(Cl) + (Me12TPP)Mn(V)(O) --> 2(Me12TPP)Mn(IV)(X) is k2=2*1E8 M-1 s-1.The rate constant for the epoxidation (k3) of norbornene was determined as (2.3+/-0.5)*1E3 M-1 s-1 while the rate constants for the epoxidation of cis-cyclooctene and cyclohexene were determined as (6.2+/-1.1)*1E2 M-1 s-1 and 1.0*1E2 M-1 s-1, respectively.The N-substituted imidazole (NAcPhIm) does not ligate to (Me12TPP)Mn(III)(Cl) when present in 580-fold excess over manganese(III) porphyrin, and its presence, up to this concentration, does not alter the second-order rate constant forreaction of ClO(1-) with the latter.The rate constant for epoxidation is also not altered by the presence of NAcPhIm, but the yields of epoxides exhibit a moderate increase.The PTC serves as a counterion to the ClO(1-) moiety and an increase in its concentration (or an impurity in this reagent) results in it behaving as a substrate for oxidation by (Me12TPP)Mn(V)(O).
Enthalpy-Entropy Compensation Effect in Oxidation Reactions by Manganese(IV)-Oxo Porphyrins and Nonheme Iron(IV)-Oxo Models
Guo, Mian,Zhang, Jisheng,Zhang, Lina,Lee, Yong-Min,Fukuzumi, Shunichi,Nam, Wonwoo
, p. 18559 - 18570 (2021/11/22)
"Enthalpy-Entropy Compensation Effect"(EECE) is ubiquitous in chemical reactions; however, such an EECE has been rarely explored in biomimetic oxidation reactions. In this study, six manganese(IV)-oxo complexes bearing electron-rich and -deficient porphyrins are synthesized and investigated in various oxidation reactions, such as hydrogen atom transfer (HAT), oxygen atom transfer (OAT), and electron-transfer (ET) reactions. First, all of the six Mn(IV)-oxo porphyrins are highly reactive in the HAT, OAT, and ET reactions. Interestingly, we have observed a reversed reactivity in the HAT and OAT reactions by the electron-rich and -deficient Mn(IV)-oxo porphyrins, depending on reaction temperatures, but not in the ET reactions; the electron-rich Mn(IV)-oxo porphyrins are more reactive than the electron-deficient Mn(IV)-oxo porphyrins at high temperature (e.g., 0 °C), whereas at low temperature (e.g., -60 °C), the electron-deficient Mn(IV)-oxo porphyrins are more reactive than the electron-rich Mn(IV)-oxo porphyrins. Such a reversed reactivity between the electron-rich and -deficient Mn(IV)-oxo porphyrins depending on reaction temperatures is rationalized with EECE; that is, the lower is the activation enthalpy, the more negative is the activation entropy, and vice versa. Interestingly, a unified linear correlation between the activation enthalpies and the activation entropies is observed in the HAT and OAT reactions of the Mn(IV)-oxo porphyrins. Moreover, from the previously reported HAT reactions of nonheme Fe(IV)-oxo complexes, a linear correlation between the activation enthalpies and the activation entropies is also observed. To the best of our knowledge, we report the first detailed mechanistic study of EECE in the oxidation reactions by synthetic high-valent metal-oxo complexes.
Formation and kinetic studies of manganese(IV)-oxo porphyrins: Oxygen atom transfer mechanism of sulfide oxidations
Klaine, Seth,Bratcher, Fox,Winchester, Charles M.,Zhang, Rui
, (2020/01/08)
Visible light irradiation of photo-labile porphyrin-manganese(III) chlorates or bromates (2) produced manganese(IV)-oxo porphyrins [MnIV(Por)(O)] (Por = porphyrin) (3) in three porphyrin ligands. The same oxo species 3 were also formed by chemical oxidation of the corresponding manganese(III) precursors (1) with iodobenzene diacetate, i.e. PhI(OAc)2. The systems under study include 5,10,15,20-tetra(pentafluorophenyl)porphyrin?manganese(IV)-oxo (3a), 5,10,15,20-tetra(2,6-difluorophenyl)porphyrin?manganese(IV)-oxo (3b), and 5,10,15,20-tetramesitylporphyrin?manganese(IV)-oxo (3c). As expected, complexes 3 reacted with thioanisoles to produce the corresponding sulfoxides and over-oxidized sulfones. The kinetics of oxygen atom transfer (OAT) reactions of these generated 3 with aryl sulfides were studied in CH3CN solutions. Second-order rate constants for sulfide oxidation reactions are comparable to those of alkene epoxidations and activated C[sbnd]H bond oxidations by the same oxo species 3. For a given substrate, the reactivity order for the manganese(IV)-oxo species was 3a > 3b > 3c, consistent with expectations on the basis of the electron-withdrawing capacity of the porphyrin macrocycles. Free-energy Hammett analyses gave near-linear correlations with σ values, indicating no significant positive charge developed at the sulfur during the oxidation process. The mechanistic results strongly suggest [MnIV(Por)(O)] reacts as a direct OAT agent towards sulfide substrates through a manganese(II) intermediate that was detected in this work. However, an alternative pathway that involves a disproportionation of 3 to form a higher oxidized manganese(V)-oxo species may be significant when less reactive substrates are present. The competition product studies with the Hammett correlation plot confirmed that the observed manganese(IV)-oxo species is not the true oxidant for the sulfide oxidations catalyzed by manganese(III) porphyrins with PhI(OAc)2.
Highly Reactive Manganese(IV)-Oxo Porphyrins Showing Temperature-Dependent Reversed Electronic Effect in C-H Bond Activation Reactions
Guo, Mian,Seo, Mi Sook,Lee, Yong-Min,Fukuzumi, Shunichi,Nam, Wonwoo
supporting information, p. 12187 - 12191 (2019/08/20)
We report that Mn(IV)-oxo porphyrin complexes, MnIV(O)(TMP) (1) and MnIV(O)(TDCPP) (2), are capable of activating the C-H bonds of hydrocarbons, including unactivated alkanes such as cyclohexane, via an oxygen non-rebound mechanism. Interestingly, 1 with an electron-rich porphyrin is more reactive than 2 with an electron-deficient porphyrin at a high temperature (e.g., 0 °C). However, at a low temperature (e.g., -40 °C), the reactivity of 1 and 2 is reversed, showing that 2 is more reactive than 1. To the best of our knowledge, the present study reports the first example of highly reactive Mn(IV)-oxo porphyrins and their temperature-dependent reactivity in C-H bond activation reactions.
Facile formation of a meso-meso linked porphyrin dimer catalyzed by a manganese(iv)-oxo porphyrin
Takai, Atsuro,Habermeyer, Benoit,Fukuzumi, Shunichi
scheme or table, p. 6804 - 6806 (2011/08/22)
A manganese(iv)-oxo porphyrin catalyzes C-C bond formation between zinc porphyrins at the meso-position with a two-electron oxidant to afford the meso-meso linked porphyrin dimer efficiently. The meso-meso linked dimer is formed via formation of the porph
Synthesis, Characterization, and Reactivity of Oxomanganese(IV) Porphyrin Complexes
Groves, John T.,Stern, Michael K.
, p. 8628 - 8638 (2007/10/02)
The preparation, isolation, and characterization of two types of oxomanganese(IV) porphyrin complexes are described.The reaction of chloro(5,10,15,20-tetramesitylporphyrinato)manganese(III) IIITPM(Cl), 1> with 1,2 equiv of tetramethylammonium hydroxyde (TMA(OH)) and 1.2 equiv of m-chloroperoxybenzoic acid (m-CPBA) in CH2Cl2 produced a second complex formulated as MnIVTPM(O) (2).The reaction of 1 in CH2Cl2 containing excess tetra-n-butylammonium hydroxide (TBA(OH)) at +1.20 V generated a stable oxomanganese(IV) porphyrin complex, IVTPM(O)(OH)> (3).When the reaction stoichiometry was altered, mixtures of complexes 2 and 3 could be prepared.The aerobic reaction of 1 in CHCl3 containing 6 N NaOH and a phase-transfer catalyst resulted in the formation of a similar complex, MnIVTMP(O)(X) (2a).The addition of excess TBA(OH) to CH2Cl2 solutions of either 2 or 2a resulted in the quantitative formation of 3.The EPR spectra of 2, 2a, and 3 all displayed a strong broad resonance at g ca. 4 and a weak unresolved signal at g ca. 2 consistent with a high-spin (S=3/2) assignment of the MnIV ions.The MnIV=O stretching frequency in 2 was identified at 754 cm-1 by FT-IR spectroscopy.In the case of 3 the MnIV=O stretching frequency was at 712 cm-1.The reaction of 2a with cis-β-methylstyrene under anaerobic conditions produced a mixture of cis- and trans-epoxide in ratio of 0.17.The reaction of 2 with cis-β-methylstyrene under aerobic conditions produced a different cis-epoxide/trans-epoxide ratio and product distribution than those of the identical reaction run under anaerobic conditions.In the presence of H2(18)O, the stereoisomeric epoxides showed a significantly different (18)O content.Further, (18)O was found to reside in the oxidation products when this reaction was carried out in the presence of (18)O2.Mechanisms for the epoxidation of olefins by 2 under anaerobic and aerobic conditions are discussed, which involve atom transfer from both oxomanganese(V) and oxomanganese(IV) species.
