Quantitative Evaluation of Lewis Acidity of Metal Ions with Different Ligands and Counterions in Relation to the Promoting Effects of Lewis Acids on Electron Transfer Reduction of Oxygen

Ohkubo, Kei; Menon, Saija C.; Orita, Akihiro; Otera, Junzo; Fukuzumi, Shunichi

doi:10.1021/jo034258u

Cited by 92 publications

(87 citation statements)

References 51 publications

(54 reference statements)

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“…The calculated OO distance decreases in the order of O 2 .− (1.343 Å) >O 2 .− Li + (1.309 Å) > O 2 .− Mg 2+ (1.297 Å) > O 2 .− Sc 3+ (1.211 Å) as the Δ E value increases 50. The Δ E value can be used as a quantitative measure of the Lewis acidity of not only metal cations with different counter anions but also neutral Lewis acids, such as organotin compounds 56. 57 In the case of Sc 3+ , the Lewis acidity decreases in the order of Sc(OTf) 3 >(TTP)ScCl (TPP 2− =dianion of tetraphenylporphyrin)>(HMPA) 3 Sc(OTf) 3 .…”

Section: Binding Of Redox‐inactive Metal Ions To O2−mentioning

confidence: 99%

Lewis Acid Coupled Electron Transfer of Metal–Oxygen Intermediates

Fukuzumi

Ohkubo

Lee

et al. 2015

Chemistry A European J

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Redox-inactive metal ions and Brønsted acids that function as Lewis acids play pivotal roles in modulating the redox reactivity of metal-oxygen intermediates, such as metal-oxo and metal-peroxo complexes. The mechanisms of the oxidative CH bond cleavage of toluene derivatives, sulfoxidation of thioanisole derivatives, and epoxidation of styrene derivatives by mononuclear nonheme iron(IV)-oxo complexes in the presence of triflic acid (HOTf) and Sc(OTf)3 have been unified as rate-determining electron transfer coupled with binding of Lewis acids (HOTf and Sc(OTf)3 ) by iron(III)-oxo complexes. All logarithms of the observed second-order rate constants of Lewis acid-promoted oxidative CH bond cleavage, sulfoxidation, and epoxidation reactions of iron(IV)-oxo complexes exhibit remarkably unified correlations with the driving forces of proton-coupled electron transfer (PCET) and metal ion-coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes were taken into account. The binding of HOTf and Sc(OTf)3 to the metal-oxo moiety has been confirmed for Mn(IV) -oxo complexes. The enhancement of the electron-transfer reactivity of metal-oxo complexes by binding of Lewis acids increases with increasing the Lewis acidity of redox-inactive metal ions. Metal ions can also bind to mononuclear nonheme iron(III)-peroxo complexes, resulting in acceleration of the electron-transfer reduction but deceleration of the electron-transfer oxidation. Such a control on the reactivity of metal-oxygen intermediates by binding of Lewis acids provides valuable insight into the role of Ca(2+) in the oxidation of water to dioxygen by the oxygen-evolving complex in photosystem II.

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Section: Binding Of Redox‐inactive Metal Ions To O2−mentioning

confidence: 99%

Lewis Acid Coupled Electron Transfer of Metal–Oxygen Intermediates

Fukuzumi

Ohkubo

Lee

et al. 2015

Chemistry A European J

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136

121

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“…Such strong binding of O 2 •− to a Lewis acidic Cu(II) center lowers the free energy of the entire process, making Cu(II)-superoxide formation possible. MCET from one-electron reductants to oxygen is related to the Lewis acidity of metal ions [45,46]. Charges and ion radii are important factors to determine the Lewis acidity of metal ions.…”

Section: Kinetics and Thermodynamics Of Formation Of Cu-o2 Complexesmentioning

confidence: 99%

“…Scandium ion, which has the smallest ion radius among the trivalent metal cations, gives the largest Δ E value (1.00 eV) [45]. The Δ E values are directly correlated with the promoting effects of metal ions in electron-transfer reactions [45,46]. However, this method can only be applied to diamagnetic metal ions, since paramagnetic metal ion complexes with O 2 •− do not generally give EPR signals because of antiferromagnetic coupling or unfavorable conditions due to the presence of an S = 1 ground state, as in the case of [(TMG) 3 tren]Cu II (O 2 •− )] + ((TMG) 3 tren = tris(2-( N -tetramethylguanidyl)ethyl)-amine [54].…”

Section: Kinetics and Thermodynamics Of Formation Of Cu-o2 Complexesmentioning

confidence: 99%

Kinetics and thermodynamics of formation and electron-transfer reactions of Cu–O2 and Cu2–O2 complexes

Fukuzumi

Karlin

2013

Coordination Chemistry Reviews

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The kinetics and thermodynamics of formation of Cu(II)-superoxo (Cu-O2) complexes by the reaction of Cu(I) complexes with dioxygen (O2) and the reduction of Cu(II)-superoxo complexes to dinuclear Cu-peroxo complexes are discussed. In the former case, electron transfer from a Cu(I) complex to O2 occurs concomitantly with binding of O2•− to the corresponding Cu(II) species. This is defined as an inner-sphere Cu(II) ion-coupled electron transfer process. Electron transfer from another Cu(I) complex to preformed Cu(II)-superoxo complexes also occurs concomitantly with binding of the the Cu(II)-peroxo species with the Cu(II) species to produce the dinuclear Cu-peroxo (Cu2-O2) complexes. The kinetics and thermodynamics of outer-sphere electron-transfer reduction of Cu2-O2 complexes are also been discussed in light of the Marcus theory of outer-sphere electron transfer.

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“…34 34 or falls between those of Sc(OTf) 3 and Y(OTf) 3 (g zz = 2.0349, DE = 0.85 eV), respectively. 8,34,62 The high Lewis acidity of 3a and 3b is enough to trigger synthetically useful reactions, since the Lewis acids with an DE value larger than 0.88 were presumed to be capable of inducing carbon-carbon bondforming reactions. 45 The Hammett indicator method [63][64][65] was also applied to determine the acidity of the complex 2a-2b and 3a-3b, and it was found that both of these Lewis …”

Section: Characterization Of Air-stable Metallocene Lewis Acidsmentioning

confidence: 99%

A mini-review on air-stable organometallic Lewis acids: synthesis, characterization, and catalytic application in organic synthesis

et al. 2012

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Organometallic Lewis acids play an important role in modern organic synthesis. How to design and synthesize highly efficient and recyclable organometallic Lewis acid catalysts that can be conveniently applied in chemical reactions are key issues for sustainable synthetic processes. In general, stronger acidity means higher catalytic activity for organometallic Lewis acids. However, with the rise in acidity, the compound becomes more susceptible to hydrolysis and cannot be recycled. Simultaneous improvement of the hygroscopic character and Lewis acidity/catalytic activity of organometallic Lewis acids is highly desirable from the standpoint of practical applications. In this mini-review, the history of air-stable organometallic Lewis acids is introduced, with emphasis on our research works on metallocene, organobismuth, and organoantimony Lewis acids to the aspects of synthesis, characterization and catalytic application in carbon-carbon bond (Friedel-Crafts acylation, Mukaiyama aldol reactions; allylation, cyclotrimerization, Mannich reactions, cross-condensation reactions) and carbon-heteroatom bond (acylation, S-S bond cleavage, glycosylation) formation reactions. In terms of stability, storage, versatile ability, high catalytic activity and chemo-/stereoselectivity, the complexes will find broad applications in organic synthesis.

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Quantitative Evaluation of Lewis Acidity of Metal Ions with Different Ligands and Counterions in Relation to the Promoting Effects of Lewis Acids on Electron Transfer Reduction of Oxygen

Cited by 92 publications

References 51 publications

Lewis Acid Coupled Electron Transfer of Metal–Oxygen Intermediates

Lewis Acid Coupled Electron Transfer of Metal–Oxygen Intermediates

Kinetics and thermodynamics of formation and electron-transfer reactions of Cu–O2 and Cu2–O2 complexes

A mini-review on air-stable organometallic Lewis acids: synthesis, characterization, and catalytic application in organic synthesis

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