Efficient C–H bond activations via O<sub>2</sub>cleavage by a dianionic cobalt(<scp>ii</scp>) complex

Nguyen, Andy I.; Hadt, Ryan G.; Solomon, Edward I.; Tilley, T. Don

doi:10.1039/c4sc00108g

Cited by 60 publications

(54 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Mass spectrometry shows an ion signal at m/z 1215.48, which corresponds to [[Mn III (salen)] 2 (OH)] + ( Figure S6). Elemental analysis shows a composition of [Mn III (salen)] 2 - 2 complex, indicating that a monomeric manganese center in the starting complex is crucial for the present reaction.…”

Section: ■ Resultsmentioning

confidence: 97%

“…Characterization of 18 2 were measured with excitation at 532 nm ( Figure 3), which is a lowest-energy tail of the visible absorption of [Mn IV (salen)] 2 (μ-O) 2 . The intense band at 636 cm −1 for [Mn IV (salen)] 2 (μ-O) 2 shifts to 611 cm −1 when Na 18 OH and 18 O 2 are used.…”

Section: ■ Resultsmentioning

confidence: 99%

“…Indeed, the monomeric Mn IV (salen)(Cl) 2 complex bearing the manganese(IV) center 59 The other control experiment to note is the addition of quinones, which altered the yield of [Mn IV (salen)] 2 (μ-O) 2 depending on the redox potential of quinones (Table 2). In the case of chloranil with highest oxidizing ability among three quinones tested, the [Mn IV (salen)] 2 (μ-O) 2 …”

Section: Inorganic Chemistrymentioning

confidence: 99%

“…The critical role of a reducing species is strongly suggested by the reactions in the presence of quinones with increasing oxidizing ability, which decrease the yield of [Mn IV (salen)] 2 (μ-O) 2 •− seems unlikely, because the cathodic reduction peak potential of Mn III (salen)(Cl) (−1.148 V vs Fc/ Fc + ) is less negative than that of O 2 (−1.622 V vs Fc/Fc + ; Figure S16). Subsequently, the Mn II (salen) complex immediately reacts with O 2 to give [Mn IV (salen)] 2 (μ-O) 2 , in which the bridging oxygen atoms are derived from O 2 (eq 4).…”

Section: Inorganic Chemistrymentioning

confidence: 99%

“…The toluene solution of Mn III (salen)(Cl) was added via a gastight syringe to the 2.0 M Na 18 OH in H 2 18 O under Ar. The organic and aqueous layers were vigorously mixed.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

See 4 more Smart Citations

Reverse Catalase Reaction: Dioxygen Activation via Two-Electron Transfer from Hydroxide to Dioxygen Mediated By a Manganese(III) Salen Complex

Kurahashi

2015

Inorg. Chem.

View full text Add to dashboard Cite

Although atmospheric dioxygen is regarded as the most ideal oxidant, O2 activation for use in oxygenation reactions intrinsically requires a costly sacrificial reductant. The present study investigated the use of aqueous alkaline solution for O2 activation. A manganese(III) salen complex, Mn(III)(salen)(Cl), in toluene reacts with aqueous KOH solution under aerobic conditions, which yields a di-μ-oxo dimanganese(IV) salen complex, [Mn(IV)(salen)]2(μ-O)2. The (18)O isotope experiments show that (18)O2 is indeed activated to give [Mn(IV)(salen)]2(μ-(18)O)2 via a peroxide intermediate. Interestingly, the (18)OH(-) ion in H2(18)O was also incorporated to yield [Mn(IV)(salen)]2(μ-(18)O)2, which implies that a peroxide species is also generated from (18)OH(-). The addition of benzyl alcohol as a stoichiometric reductant selectively inhibits the (18)O incorporation from (18)OH(-), indicating that the reaction of Mn(III)(salen)(Cl) with OH(-) supplies the electrons for O2 reduction. The conversion of both O2 and OH(-) to a peroxide species is exactly the reverse of a catalase-like reaction, which has a great potential as the most efficient O2 activation. Mechanistic investigations revealed that the reaction of Mn(III)(salen)(Cl) with OH(-) generates a transient species with strong reducing ability, which effects the reduction of O2 by means of a manganese(II) intermediate.

show abstract

Section: ■ Resultsmentioning

confidence: 97%

Section: ■ Resultsmentioning

confidence: 99%

Section: Inorganic Chemistrymentioning

confidence: 99%

Section: Inorganic Chemistrymentioning

confidence: 99%

“…The toluene solution of Mn III (salen)(Cl) was added via a gastight syringe to the 2.0 M Na 18 OH in H 2 18 O under Ar. The organic and aqueous layers were vigorously mixed.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

See 3 more Smart Citations

Reverse Catalase Reaction: Dioxygen Activation via Two-Electron Transfer from Hydroxide to Dioxygen Mediated By a Manganese(III) Salen Complex

Kurahashi

2015

Inorg. Chem.

View full text Add to dashboard Cite

show abstract

Recent Developments in Dehydrogenative Organic Transformations Catalyzed by Homogeneous Phosphine‐Free Earth‐Abundant Metal Complexes

et al. 2021

View full text Add to dashboard Cite

Stoichiometric amounts of various oxidants have long been employed for the oxidation of organic compounds. The major drawback of this method is the amount of toxic waste produced, which is in sharp contrast to principles of green chemistry. In catalytic dehydrogenation pathways, hydrogen carrier organic compounds (HCOCs) containing O−H, C−H, and N−H bonds can be transformed to their oxidized forms by removing two hydrogen atoms from the starting materials. Among the homogeneous transition metal‐ligand complexes that have been applied in a catalytic dehydrogenative approach, phosphine ligands have frequently been used. Over the past decades, phosphine‐free ligand systems have since been developed and implemented in various organic reactions to overcome the drawbacks associated with phosphine‐based catalysts. The aim of this review is to summarize the use of non‐phosphinic ligand‐metal complexes in organic transformations proceeding by a dehydrogenative pathway.

show abstract

Spectroscopic Capture and Reactivity of a Low‐Spin Cobalt(IV)‐Oxo Complex Stabilized by Binding Redox‐Inactive Metal Ions

et al. 2014

View full text Add to dashboard Cite

High-valent cobalt-oxo intermediates are proposed as reactive intermediates in a number of cobalt complex-mediated oxidation reactions. Herein we report the spectroscopic capture of low-spin (S = 1/2) Co(IV)-oxo species in the presence of redox-inactive metal ions, such as Sc 3+ , Ce 3+ , Y 3+ , and Zn 2+ and investigation of their reactivity in C-H bond activation and sulfoxidation reactions. Theoretical calculations predict that the binding of Lewis-acidic metal ions to the cobalt-oxo core increases the electrophilicity of the oxygen atom, resulting in the redox tautomerism of a highly unstable [(TAML)Co III -(O • )] 2− species to a more stable [(TAML)Co IV -(O)(M n+ )] core. The present report supports the proposed role of the redox-inactive metal ions in facilitating formation of high-valent metal-oxo cores as a necessary step for oxygen evolution in chemistry and biology. KeywordsCobalt; Oxo ligand; Lewis acid stabilization; Redox tautomerization; Oxygenation High-valent metal-oxo complexes have been implicated as active oxidants in oxygenation and water oxidation reactions by a number of biological and chemical catalysts. 1 Although high-valent terminal metal-oxo complexes of groups 3-8 are ubiquitous, isolation of metaloxo species to the right of group 8 (also known as the "oxo wall" for C4v symmetry) has only been achieved for heavy transition metals like iridium 2 and platinum. 3 For example, high-valent terminal metal-oxo complexes of the lighter analogues like cobalt, nickel, and copper still remain elusive, although they are often invoked as highly reactive transient * Prof. Dr. Wonwoo Nam, Dr. Kallol Ray wwnam@ewha.ac.kr, kallol.ray@chemie.hu-berlin.de.Supporting information for this article, including Experimental section, Tables S1 -S8 and Figures S1 -S17, is available on the WWW under http://dx.doi.org/10.1002/anie.201xxxxxx. Tables S1-S2 and Figures S1-S2). Complex 1 is paramagnetic with S = 1 (μ eff = 3.1 Bohr magnetons) ground state, as expected for a Co(III) ion in the observed square planar geometry. Cyclic voltammetry (CV) of 1 at 25 °C in CH 3 CN reveals a reversible oxidation wave centered at 1.00 V vs saturated calomel electrode (SI, Figure S3); coulometric measurements show that the oxidation corresponds to a 1e -process. The reversibility of this oxidation wave at room temperature suggests that a formal Co(IV) state is thermally and kinetically accessible. HHS Public AccessIn agreement with the electrochemical data, 1 is readily oxidized in the presence of cerium ammonium nitrate (CAN) in acetone at 5 °C to form a metastable blue species (2-Ce) with a half-life (t 1/2 ) of 20 min (SI, Figure S4, inset). The blue color is associated with a band at 600 nm (ε = 7200 M −1 cm −1 ) with a shoulder near 730 nm (SI, Figure S4). We tentatively assign these bands to be ligand to metal charge transfer (LMCT) in origin, which presumably arise from transitions from the amide nitrogens of TAML to the Co(IV) center in 2-Ce; as expected, these bands are significantly blue-shifted in the corre...

show abstract

Efficient C–H bond activations via O₂cleavage by a dianionic cobalt(ii) complex

Cited by 60 publications

References 48 publications

Reverse Catalase Reaction: Dioxygen Activation via Two-Electron Transfer from Hydroxide to Dioxygen Mediated By a Manganese(III) Salen Complex

Reverse Catalase Reaction: Dioxygen Activation via Two-Electron Transfer from Hydroxide to Dioxygen Mediated By a Manganese(III) Salen Complex

Recent Developments in Dehydrogenative Organic Transformations Catalyzed by Homogeneous Phosphine‐Free Earth‐Abundant Metal Complexes

Spectroscopic Capture and Reactivity of a Low‐Spin Cobalt(IV)‐Oxo Complex Stabilized by Binding Redox‐Inactive Metal Ions

Contact Info

Product

Resources

About

Efficient C–H bond activations via O2cleavage by a dianionic cobalt(ii) complex

Cited by 60 publications

References 48 publications

Reverse Catalase Reaction: Dioxygen Activation via Two-Electron Transfer from Hydroxide to Dioxygen Mediated By a Manganese(III) Salen Complex

Reverse Catalase Reaction: Dioxygen Activation via Two-Electron Transfer from Hydroxide to Dioxygen Mediated By a Manganese(III) Salen Complex

Recent Developments in Dehydrogenative Organic Transformations Catalyzed by Homogeneous Phosphine‐Free Earth‐Abundant Metal Complexes

Spectroscopic Capture and Reactivity of a Low‐Spin Cobalt(IV)‐Oxo Complex Stabilized by Binding Redox‐Inactive Metal Ions

Contact Info

Product

Resources

About

Efficient C–H bond activations via O₂cleavage by a dianionic cobalt(ii) complex