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Introducing HAT mediator boosted the oxidation activity of toluene to benzaldehyde on the Pd loaded BiVO 4 photocatalyst under blue-to-green light irradiation, along with good selectivity. [Display omitted] • N -hydroxy compounds were applied to toluene oxidation using Pd-loaded BiVO 4 photocatalyst. • Introduction of N -hydroxyphthalimide boosted the activity up to ca. 28 times. • Excellent efficiency (apparent quantum yield = 10.8% at 420 nm and 5.4% at 520 nm) was realized. • The use of nanoparticulate Pd-loaded BiVO 4 was also effective to improve the photocatalytic activity. • Addition of N -hydroxyphthalimide also resulted in good selectivity (>99 %) of benzaldehyde production. Selective organic conversion using semiconductor photocatalysts has been focused on the viewpoint of sustainable synthesis processes. Especially, C-H activation is one of the most attractive reactions. We recently reported photo-oxidation of toluene to benzaldehyde over visible-light responsible Pd-loaded BiVO 4 (Pd/BiVO 4) photocatalyst. However, it remains challenging due to its low efficiency. Herein, we introduce a novel strategy to apply a cyclic nitroxide compound as an efficient redox mediator along with Pd/BiVO 4 for toluene oxidation. Including N -hydroxyphthalimide (NHPI) could significantly expedite the activity of benzaldehyde production up to ca. 28 times compared to without NHPI under blue-to-green light irradiation. The sustainable conditions realized a conversion in high efficiency (apparent quantum yield = 10.8 and 5.4 %@420 and 520 nm, respectively) and with excellent selectivity (>99 %). The excellent efficiency was realized by the synergistic effect between the presence of NHPI and the use of nanoparticulate Pd/BiVO 4 with a relatively large surface area. [ABSTRACT FROM AUTHOR]

A dicopper(II) complex, stabilized by the bis(tpa) ligand 1,2-bis[2-[bis(2-pyridylmethyl)aminomethyl]-6-pyridyl]ethane (6-hpa), [Cu2(μ-OH)(6-hpa)]3+, was synthesized and structurally characterized. This complex catalyzed selective hydroxylation of benzene to phenol using H2O2, thus attaining large turnover numbers (TONs) and high H2O2 efficiency. The TON after 40 hours for the phenol production exceeded 12000 in MeCN at 50 °C under N2, the highest value reported for benzene hydroxylation with H2O2 catalyzed by homogeneous complexes. At 22 % benzene conversion, phenol (95.2 %) and p-benzoquinone (4.8 %) were produced. The mechanism of H2O2 activation and benzene hydroxylation is proposed. [ABSTRACT FROM AUTHOR]

Recently, it was shown that μ-oxo-μ-peroxodiiron(III) is converted to high-spin μ-oxodioxodiiron(IV) through O−O bond scission. Herein, the formation and high reactivity of the anti-dioxo form of high-spin μ-oxodioxodiiron(IV) as the active oxidant are demonstrated on the basis of resonance Raman and electronic-absorption spectral changes, detailed kinetic studies, DFT calculations, activation parameters, kinetic isotope effects (KIE), and catalytic oxidation of alkanes. Decay of μ-oxodioxodiiron(IV) was greatly accelerated on addition of substrate. The reactivity order of substrates is toluene8]toluene is 95 at −30 °C, which the largest in diiron systems reported so far. The present diiron complex efficiently catalyzes the oxidation of various alkanes with H2O2. [ABSTRACT FROM AUTHOR]

We have reported previously that an iron(III) complex supported by an anionic pentadentate monoamido ligand, dpaqH (dpaqH=2-[bis(pyridin-2-ylmethyl)]amino- N-quinolin-8-yl-acetamido), promotes selective CH hydroxylation with H2O2 with high regioselectivity. Herein, we report on the preparation of FeIII-dpaq derivatives that have a series of substituent groups at the 5-position of a quinoline moiety in the parent ligand dpaqH (dpaqR, R: OMe, H, Cl, and NO2), and examine them with respect to their catalytic activity in CH hydroxylation with H2O2. As the substituent group becomes more electron-withdrawing, both the selectivity and the turnover number increase, but the selectivity of epoxidation shows the opposite trend. [ABSTRACT FROM AUTHOR]

Abstract: Fe(II)–tris(2-pyridylmethyl)amine complexes, Fe(II)–tpa, having different co-existing anions, [Fe(tpa)(MeCN)2](ClO4)2 (1), [Fe(tpa)(MeCN)2](CF3SO3)2 (2) and [Fe(tpa)Cl2] (3), were prepared. Effective magnetic moments (evaluated by the Evans method) revealed that while 1–3 in acetone and 3 in acetonitrile (MeCN) have a high-spin Fe(II) ion at 298K, the Fe(II) ions of 1 and 2 are in the low-spin state in MeCN. The aerobic oxidation of 1–3 was monitored by UV–Vis spectral changes in acetone or MeCN under air at 298K. Only the high-spin Fe(II)–tpa complexes were oxidized with rate constants of k obs =0.1–1.3h−1, while 1 and 2 were stable in MeCN. The aerobic oxidation of 1 or 2 in acetone was greatly accelerated in the presence of pure, peroxide-free cyclohexene (1000equiv.) and yielded a large amount of oxidized products; 2-cyclohexe-1-ol (A) and 2-cyclohexene-1-one (K) (A+K: 23940% yield based on Fe; A/K=0.3), and cyclohexene oxide (810%). Besides cyclohexene, aerobic oxidation of norbornene, cyclooctene, ethylbenzene, and cumene proceeded in the presence of 1 in acetone at 348K without any reductant. Essential factors in the reaction are high-spin Fe(II) ion and labile coordination sites, both of which are required to generate Fe(II)-superoxo species as active species for the H-atom abstraction of hydrocarbons. [Copyright &y& Elsevier]

Basic nanospace was synthesized by the homogeneous modification of FSM-16 with 3-(triethoxysilyl)pyridine, which is a rigid substrate without an alkyl chain as linker. Aldol condensation of butanal gave the corresponding dimer in high yields over 3-(triethoxysilyl)pyridine-modified FSM-16. A copper-pyridine complex was immobilized within the interior of FSM-16 using the modified pyridyl group as a ligand and the oxidative coupling polymerization of 2,5-dimethylphenol proceeded with high regio-selectivity. Graphical Abstract: Basic nanospace was synthesized by the homogeneous modification of FSM-16 with 3-(triethoxysilyl)pyridine, which is a rigid substrate without an alkyl chain as linker. Aldol condensation of n-butyraldehyde gave the corresponding dimer in high yields over 3-(triethoxysilyl)pyridine-modified FSM-16. A copper-pyridine complex was immobilized within the interior of FSM-16 using a modified pyridyl group as the ligand and the oxidative polymerization of 2,5-dimethylphenol proceeded with high regio-selectivity.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Kinetic study was carried out for photo-oxidation of NH3 (photo-SCO: 4NH3 +3O2 →2N2 +6H2O) to elucidate the mechanisms of the photo-SCO over anatase and rutile TiO2. The reaction orders of the reactant gases reveal that the photo-SCO activity depends only on the concentration of O2 with either anatase or rutile TiO2. Steady-state kinetics suggests that the rate-determining step is the formation of nitrosoamide species from surface NO species and NH2 radical. The surface NO species may play an important role in the high activity of the photo-SCO. O3 anion radical, which is a strong oxidant, was detected only over anatase TiO2 and the concentration of surface NO species would be increased by O3 anion radical. This may be the reason why anatase TiO2 shows higher activity than rutile TiO2. The photo-SCO activity is enhanced as the reaction temperature increased. 100% NH3 conversion and 94% N2 selectivity were achieved at GHSV=50,000h−1 at 435K. This enhancement of the activity at higher reaction temperature is caused by (1) the increase in the surface NO species and (2) the improvement of reactivity between surface NO and NH2 radical. The SCO activity is moderately high even at low temperature: the Arrhenius activation energy is only 24.4kJmol−1. [Copyright &y& Elsevier]

A 3,5-di-tert-butyl-1,2-semiquinonato (DTBSQ) adduct of Mn(II) was prepared by a reaction between MnII(TPA)Cl2 (TPA = tris(pyridin-2-ylmethyl)amine) and DTBSQ anion and was isolated as a tetraphenylborate salt. The X-ray crystal structure revealed that the complex is formulated as a manganese(II)-semiquinonate complex [MnII(TPA)(DTBSQ)]+ (1). The electronic spectra in solution also indicated the semiquinonate coordination to Mn. The exposure of 1 in acetonitrile to dioxygen afforded 3,5-di-tert-butyl-1,2-benzoquione and a bis(mu;-oxo)dimanganese(III,III) complex [MnIII2(mu;-oxo)2(TPA)2]2+ (2). The reaction of 2 with 3,5-di-tert-butylcatechol (DTBCH2) quantitatively afforded two equivalents of 1 under anaerobic conditions. The highly efficient catalytic oxidation of DTBCH2 with dioxygen was achieved by combining the above two reactions, that is, by constructing a catalytic cycle involving both manganese complexes 1 and 2. It was revealed that dioxygen is reduced to water but not to hydrogen peroxide in the catalytic cycle. [ABSTRACT FROM AUTHOR]

• Semiconductor photocatalysts, BiVO 4 , selectively oxidize toluene to benzaldehyde under visible-light irradiation. • The oxidation activity depended on the type and amounts of co-catalyst loaded. • Pd(0.1 wt%) loaded BiVO 4 photocatalyst showed the highest performance. • Pd/BiVO 4 particles were reusable for the photo-oxidation of toluene. • The reaction proceeded under light irradiation up to 520 nm, which corresponds to green-light. Selective synthesis of organic chemicals such as oxidation of toluene to benzaldehyde using sunlight is necessary for its sustainable and environment-friendly applications. The photocatalytic reaction using semiconductor photocatalysts is a promising approach for sunlight-induced organic synthesis due to its significant advantages of operation under mild conditions, stability, and recyclicity. TiO 2 is one of the most widely studied photocatalysts; however, the low selectivity for partial oxidation due to the complete decomposition to CO 2 and lack of utilization of visible-light hampers its practical application. Here, we successfully demonstrated selective oxidation of toluene to benzaldehyde using a Pd-loaded BiVO 4 photocatalyst under visible light irradiation. Furthermore, we confirmed that the reaction proceeds even under light irradiation up to 520 nm; this is the first report using blue-to-green light-responsive semiconductor photocatalyst for converting toluene to benzaldehyde. Achieving efficient organic synthesis under visible light using semiconductor photocatalyst is an important step toward solar-to-chemical conversion. [ABSTRACT FROM AUTHOR]

C−H Activation The formation and high reactivity of the anti‐dioxo form of high‐spin μ‐oxodioxodiiron(IV) as the active oxidant are demonstrated on the basis of resonance Raman and electronic‐absorption spectral changes, detailed kinetic studies, DFT calculations, activation parameters, kinetic isotope effects (KIE), and catalytic oxidation of alkanes. These results provide insight into the high reactivity of the active species Q of soluble methane monooxygenases and the development of efficient alkane oxidation catalysts. For more details, see the Full Paper by M. Kodera et al. on page 5924 ff. [ABSTRACT FROM AUTHOR]