Catalysts for selective aerobic oxidation under ambient conditions

Boring, Eric; Geletii, Yurii V.; Hill, Craig L.

doi:10.1007/0-306-47816-1_5

Cited by 10 publications

(6 citation statements)

References 57 publications

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“…Selective oxidation reactions are utilized for transformations of small molecules in applications ranging from benchtop-scale laboratory synthesis, to pharmaceuticals production, to the manufacture of petroleum products. − Molecular oxygen is the ideal inexpensive and environmentally benign oxidant, and there are now many examples of selective and powerful transition metal catalysts for aerobic partial oxidations of organic substrates. − Although many of these synthetic systems are well understood, the chemical features that engender selective O 2 reduction are often not easily transferrable to other classes of oxidation catalysts. Therefore, the development of general methods for activation of O 2 presages systematic development of new catalytic cycles for aerobic oxidations of small organic molecules.…”

Section: Introductionmentioning

confidence: 99%

Redox-Active Ligands Facilitate Bimetallic O₂Homolysis at Five-Coordinate Oxorhenium(V) Centers

et al. 2010

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Five-coordinate oxorhenium(V) anions with redox-active catecholate and amidophenolate ligands are shown to effect clean bimetallic cleavage of O(2) to give dioxorhenium(VII) products. A structural homologue with redox-inert oxalate ligands does not react with O(2). Redox-active ligands lower the kinetic barrier to bimetallic O(2) homolysis at five-coordinate oxorhenium(V) by facilitating formation and stabilization of intermediate O(2) adducts. O(2) activation occurs by two sequential Re-O bond forming reactions, which generate mononuclear eta(1)-superoxo species, and then binuclear trans-mu-1,2-peroxo-bridged complexes. Formation of both Re-O bonds requires trapping of a triplet radical dioxygen species by a cis-[Re(V)(O)(cat)(2)](-) anion. In each reaction the dioxygen fragment is reduced by 1e(-), so generation of each new Re-O bond requires that an oxometal fragment is oxidized by 1e(-). Complexes containing a redox-active ligand access a lower energy reaction pathway for the 1e(-) Re-O bond forming reaction because the metal fragment can be oxidized without a change in formal rhenium oxidation state. It is also likely that redox-active ligands facilitate O(2) homolysis by lowering the barrier to the formally spin-forbidden reactions of triplet dioxygen with the closed shell oxorhenium(V) anions. By orthogonalizing 1e(-) and 2e(-) redox at oxorhenium(V), the redox-active ligand allows high-valent rhenium to utilize a mechanism for O(2) activation that is atypical of oxorhenium(V) but more typical for oxygenase enzymes and models based on 3d transition metal ions: O(2) cleavage occurs by a net 2e(-) process through a series of 1e(-) steps. The implications for design of new multielectron catalysts for oxygenase-type O(2) activation, as well as the microscopic reverse reaction, O-O bond formation from coupling of two M=O fragments for catalytic water oxidation, are discussed.

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Section: Introductionmentioning

confidence: 99%

Redox-Active Ligands Facilitate Bimetallic O₂Homolysis at Five-Coordinate Oxorhenium(V) Centers

et al. 2010

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“…The relative efficacy by which a sulfide molecule is oxidized by one versus the other pathways appears to be dependent on the nature of the transition metal catalyst, solvent and temperature. Despite mechanistic studies of porphyrin catalysts being very limited, high-valent metalloporphyrin-oxo intermediates were considered as main active oxygen-containing intermediates [108,[110][111][112]. Our data do not contradict this hypothesis because the oxidation is more rapid in the presence of the Mn(III) complex, as was shown in the "hot filtration test."…”

Section: Catalytic Reactionsmentioning

confidence: 43%

Hybrid Materials Based on Imidazo[4,5-b]porphyrins for Catalytic Oxidation of Sulfides

et al. 2023

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Heterogenized metalloporphyrin catalysts for oxidation reactions are extensively explored to improve chemical production. In this work, manganese meso-tetraarylporphyrins were immobilized on hydrated mesoporous titanium dioxide (SBET = 705 m2 g−1) through carboxylate or phosphonate anchoring groups separated from the macrocycle by the 2-arylimidazole linker fused across one of the pyrrolic rings of the macrocycle. The element composition of two mesoporous hybrid materials thus obtained were investigated and the integrity of the immobilized complexes was shown by different physicochemical methods. Finally, the catalytic efficiency of the more stable material Mn(TMPIP)/TiO2 with the phosphonate anchor was evaluated in the selective oxidation of sulfides to sulfoxides by molecular oxygen in the presence of isobutyraldehyde (IBA). The heterogenized complex has shown excellent catalytic activity exhibiting a turnover (TON) of ~1100 in a single catalytic run of the sulfoxidation of thioanisole. The catalyst was successfully reused in seven consecutive catalytic cycles.

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“…Air-based catalytic organic oxidations have attracted much attention recently, because they utilize only ambient O 2 , which is less expensive and more abundant than other oxidants and generates few if any deleterious byproducts. − Moreover, aerobic organic oxidation reactions are very attractive for decontamination of a wide variety of toxic compounds in human environments, including TICs ,− and chemical warfare agents (CWAs), , under mild conditions. Therefore, the aerobic catalytic oxidation of formaldehyde to formic acid, CO, and/or CO 2 under ambient conditions is very attractive from multiple vantages …”

Section: Introductionmentioning

confidence: 99%

Aerobic Oxidation of Formaldehyde Catalyzed by Polyvanadotungstates

Guo

Luo

et al. 2014

ACS Catal.

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Three tetra-n-butylammonium (TBA) salts of polyvanadotungstates, [n-Bu4N]6[PW9V3O40] (PW 9 V 3 ), [n-Bu4N]5H2PW8V4O40 (PW 8 V 4 ), and [n-Bu4N]4H5PW6V6O40·20H2O (PW 6 V 6 ), have been synthesized and shown to be effective catalysts for the aerobic oxidation of formaldehyde to formic acid under ambient conditions. These complexes, characterized by elemental analysis, Fourier transform infrared spectroscopy, UV–vis spectroscopy, and thermogravimetric analysis, exhibit a catalytic activity for this reaction comparable to those of other polyoxometalates. Importantly, they are more effective in the presence of water than the metal oxide-supported Pt and/or Au nanoparticles traditionally used as catalysts for formaldehyde oxidation in the gas phase. The polyvanadotungstate-catalyzed oxidation reactions are first-order in formaldehyde, parabolic-order (slow, fast, and slow again) in catalyst, and zero-order in O2. Under optimized conditions, a turnover number of ∼57 has been obtained. These catalysts can be recycled and reused without a significant loss of catalytic activity.

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Catalysts for selective aerobic oxidation under ambient conditions

Cited by 10 publications

References 57 publications

Redox-Active Ligands Facilitate Bimetallic O₂Homolysis at Five-Coordinate Oxorhenium(V) Centers

Redox-Active Ligands Facilitate Bimetallic O₂Homolysis at Five-Coordinate Oxorhenium(V) Centers

Hybrid Materials Based on Imidazo[4,5-b]porphyrins for Catalytic Oxidation of Sulfides

Aerobic Oxidation of Formaldehyde Catalyzed by Polyvanadotungstates

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Catalysts for selective aerobic oxidation under ambient conditions

Cited by 10 publications

References 57 publications

Redox-Active Ligands Facilitate Bimetallic O2Homolysis at Five-Coordinate Oxorhenium(V) Centers

Redox-Active Ligands Facilitate Bimetallic O2Homolysis at Five-Coordinate Oxorhenium(V) Centers

Hybrid Materials Based on Imidazo[4,5-b]porphyrins for Catalytic Oxidation of Sulfides

Aerobic Oxidation of Formaldehyde Catalyzed by Polyvanadotungstates

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Redox-Active Ligands Facilitate Bimetallic O₂Homolysis at Five-Coordinate Oxorhenium(V) Centers

Redox-Active Ligands Facilitate Bimetallic O₂Homolysis at Five-Coordinate Oxorhenium(V) Centers