Diphenylmethane Oxidation Catalyzed by Mononuclear Mn(III) Complexes

Catalytic property of a series of manganese(III) complexes with tetradentate phenol‐ and pyridinebased ligands on the oxidation of the C‐H bond of diphenylmethane in the presence of hydrogen peroxide as an oxidant at ambient conditions were investigated. In this process, diphenylmethane was oxidized to the corresponding keton and alcohol. The catalytic selectivity of the complexes was evaluated.     

Bromo-substituted Mn(II) and Mn(III)-tetraarylporphyrins: synthesis and properties

Abstract

Mono-, tetra-, and octa-bromo substituted Mn(II)- and Mn(III)-tetraarylporphyrins were synthesized by reactions of manganese(II) chloride with corresponding porphyrin ligands or their Cd(II)-complexes in DMF. With the use of the metal exchange reaction, the time of the Mn-porphyrins formation is significantly reduced with increase in yield of final products in comparison with the complexation reaction. Mn(III)-tetraarylporphyrins reduce to the Mn(II)-porphyrins in DMF in the presence of NaOH and in pure DMF. The obtained compounds were identified using UV–vis and ¹H NMR spectroscopy, mass-spectrometry, and elemental analysis.     

The Spectrophotometry Determination of Mn(III) in the Presence of Mn(IV)

Abstract

The spectra of complex of Mn(III) and Mn(IV) with pyrophosphoric acid are investigated. The molar absorption coefficient of the complex of Mn(III) with pyrophosphoric acid is 80.6/Mcm at 510nm which is close to that of Mn(IV), 110/Mcm, however, the molar absorption coefficient of the complex of Mn(HI) with pyrophosphoric acid is only 4.98/Mcm at 398nm which is much less than that of Mn(IV), 390/Mcm. Based on this absorbance difference between Mn(III) and Mn(IV) at wavelength 398nm and 510nm, a procedure of determination of Mn(III) in the presence of Mn(IV) has been developed.     

Triazine based Mn (II) and Mn (II)/Ln (III) complexes: Synthesis,characterization and catecholase activities

In the current work, two triazine‐based multidentate ligands (H₂L¹ and H₂L²) and their homo‐dinuclear Mn (II), mononuclear Ln (III) and hetero‐dinuclear Mn (II)/Ln (III) (Where Ln: Eu or La) complexes were synthesized and characterized by spectroscopic and analytical methods. Single crystals of a homo‐dinuclear Mn (II) complex {[Mn (HL¹)(CH₃OH)](ClO₄·CH₃OH}₂ ( 1 ) were obtained and the molecular structure was determined by X‐ray diffraction method. In the structure of the complex, each Mn (II) ion is seven‐coordinate and one of the phenolic oxygen bridges two Mn (II) centre forming a dimeric structure. The UV–Vis. and photoluminescence properties of synthesized ligands and their metal complexes were investigated in DMF solution and the compounds showed emission bands in the UV–Vis. region. The catecholase enzyme‐like activity of the complexes were studied for 3,5‐DTBC → 3,5‐DTBQ conversion in the presence of air oxygen. Homo‐dinuclear Mn (II) complexes ( 1 and 4 ) were found to efficiently catalyse 3,5‐DTBC → 3,5‐DTBQ conversion with the turnover numbers of 37.25 and 35.78 h^?1 (k_cat), respectively. Mononuclear Eu (III) and La (III) complexes did not show catecholase activity.     

具有扩展的双链结构的Mn(III)酰腙配合物的合成和晶体结构

合成了含有水杨醛缩(4-甲氧基)苯氧乙酰腙(以下简写为 H2L)的锰配合物[Mn(L)(acac)-(EtOH)]?H2O (MnC23H29 N2O8, Mr = 516.42)。配合物晶体属三斜晶系, 空间群为 P1, 晶胞参数为:a = 7.6942(3), b = 11.2422(4), c = 14.9230(6) ?, α = 95.656(2), β = 104.848(2), γ = 95.642(2)°, V =1231.37(8) ?3, Z = 2, Dc = 1.393 g/cm3, μ = 0.585 mm–1, F(000) = 540。对于 4374 (I > 2σ(I)) 个可观察点, R = 0.0439, wR = 0.1150。在配合物中, 中心 Mn(III)离子具有扭曲的 NO5八面体配位构型。晶体通过分子内与分子间的氢键作用形成平行排列的无限双链结构。     

以氯醌酸二价阴离子为桥联配体的Fe(Ⅲ)-Fe(Ⅲ)和Mn(Ⅱ)-Mn(Ⅱ)双核配合物的合成与磁性

基于铁和锰的双核配合物在生物氧化还原过程中的重要作用及在化学的氧化还原过程中可能做为催化剂的应用前景,本文合成了两个新的以氯醌酸二价阴离子为桥联配体的Fe(Ⅲ)双核和Mn(Ⅱ)双核配合物:[Fe_2(phen)_4(μ-CA)](ClO_4)_4·2H_2O(1)和[Mn_2(phen)_4(μ-CA)](ClO_4)_2·3H_2O(2)(phen=1,10菲咯啉;CA=氯醌酸二价阴离子)。经元素分析、IR、电子光谱及磁性等测定,对两配合物进行了表征。     

Mn(III)-catalyzed oxidation of sulfides to sulfoxides with hydrogen peroxide

Sulfides were selectively oxidized to the corresponding sulfoxides in good yields with hydrogen peroxide using a manganese(III) Schiff-base complex as a catalyst in glacial acetic acid as solvent under mild conditions.     

An Efficient Aerobic Oxidation for p-Xylene to p-Toluic Acid using Azacrown Ether-tethered Mn(III) Schiff Base Complexes as Catalysts

The oxidation of p-xylene to p-toluic acid with air at 110°C under normal atmospheric pressure occurs efficiently in the presence of crown Mn(III) Schiff base complexes [Formula: See Text] (n=1-4). Significant conversion levels (up to 75%) and selectivity (up to 92-96%) are obtained; the effect of the azacrown ether pendants in Mn(III) Schiff base complexes on the oxidation of p-xylene are also investigated by comparison with the crown-free analogues [Formula: See Text] Moreover, addition of alkali metal ions accelerates the rate of conversion of p-xylene to p-toluic acid.     

A Review of Manganese(III) (Oxyhydr)Oxides Use in Advanced Oxidation Processes

The key role of trivalent manganese (Mn(III)) species in promoting sulfate radical-based advanced oxidation processes (SR-AOPs) has recently attracted increasing attention. This review provides a comprehensive summary of Mn(III) (oxyhydr)oxide-based catalysts used to activate peroxymonosulfate (PMS) and peroxydisulfate (PDS) in water. The crystal structures of different Mn(III) (oxyhydr)oxides (such as α-Mn₂O₃, γ-MnOOH, and Mn₃O₄) are first introduced. Then the impact of the catalyst structure and composition on the activation mechanisms are discussed, as well as the effects of solution pH and inorganic ions. In the Mn(III) (oxyhydr)oxide activated SR-AOPs systems, the activation mechanisms of PMS and PDS are different. For example, both radical (such as sulfate and hydroxyl radical) and non-radical (singlet oxygen) were generated by Mn(III) (oxyhydr)oxide activated PMS. In comparison, the activation of PDS by α-Mn₂O₃ and γ-MnOOH preferred to form the singlet oxygen and catalyst surface activated complex to remove the organic pollutants. Finally, research gaps are discussed to suggest future directions in context of applying radical-based advanced oxidation in wastewater treatment processes.     

Advanced Synthesis of Dihydrofurans: Effect of Formic Acid on the Mn(III)-Based Oxidation

The Mn(III)-based oxidation of a tertiary alkylamine, such as nitrilotris(ethane-2,1-diyl) tris(3-oxobutanoate) (1) with 1,1-diphenylethene (2a), effectively proceeded in an acetic acid–formic acid mixed solvent to give nitrilotris(ethane-2,1-diyl) tris(2-methyl-5,5-diphenyl-4,5-dihydrofuran-3-carboxylate) (3). Other typical Mn(III)-based reactions of various β-diketo esters 4a–e, 2,4-pentanedione (6a), malonic acid (6b), and diethyl malonate (6c) with 1,1-diarylthenes 2a–d were also investigated in a similar acetic acid–formic acid mixed solvent and the reaction rate was accelerated and the product yield increased.     

离子液体中Mn（Salen）催化仲醇的氧化反应研究

以PhI(OAc)2为氧化剂,考察了1,3-二烷基咪唑硫酸酯系列离子液体中Mn(Salen)催化仲醇氧化的反应. 结果表明, 在MMISM-CH2Cl2(1:4,v:v)混合溶剂中, 反应条件为n((-苯乙醇): n(醋酸碘苯): n(催化剂1c)=50: 70: 1时, (-苯乙醇的转化率可以达到97.8%, 产物苯乙酮的选择性为100%, 远高于在纯CH2Cl2中的结果, 也要好于[bmim]BF4和[bmim]PF6对该反应的促进作用. 此外, BMISM及BEISE对催化剂1c有较好的稳定作用,催化剂可以重复使用.     

1-甲基-2-咪唑醛肟锰(III)配合物的合成、晶体结构及电化学性质研究

采用溶剂扩散法获得了锰(III)的两个单核配合物 [Mn(Miao)2(H2O)2]ClO4(1)和[Mn(Miao)2(DMF)2]ClO4(2)（HMiao = 1-甲基-2-咪唑醛肟,DMF = N,N-二甲基甲酰胺）的晶体。X-射线衍射单晶结构表明：两种配合物均属三斜晶系,空间群Pī,锰与配位原子形成稳定的八面体结构。采用Gaussian03W程序计算了HMiao配体的电荷密度,理论计算与实际配位形式完全吻合。通过循环伏安法测定了两种锰配合物在DMF 溶液中的电化学性质。     

Mechanistic aspects of uncatalyzed and ruthenium(III) catalyzed oxidation of dl-ornithine by copper(III) periodate complex in aqueous alkaline medium: A comparative kinetic study

The oxidation of dl-ornithine monohydrochloride (OMH) by diperiodatocuprate(III) (DPC) has been investigated both in the absence and presence of ruthenium(III) catalyst in aqueous alkaline medium at a constant ionic strength of 0.20 mol dm⁻³ spectrophotometrically. The stiochiometry was same in both the cases, i.e., [OMH]/[DPC] = 1:4. In both the catalyzed and uncatalyzed reactions, the order of the reaction with respect to [DPC] was unity while the order with respect to [OMH] was < 1 over the concentration range studied. The rate increased with an increase in [OH⁻] and decreased with an increase in [IO₄⁻] in both cases. The order with respect to [Ru(III)] was unity. The reaction rates revealed that Ru(III) catalyzed reaction was about eight-fold faster than the uncatalyzed reaction. The oxidation products were identified by spectral analysis. Suitable mechanisms were proposed. The reaction constants involved in the different steps of the reaction mechanisms were calculated for both cases. The catalytic constant (K_C) was also calculated for catalyzed reaction at different temperatures. The activation parameters with respect to slow step of the mechanism and also the thermodynamic quantities were determined. Kinetic experiments suggest that [Cu(H₂IO₆)(H₂O)₂] is the reactive copper(III) species and [Ru(H₂O)₅OH]²⁺ is the reactive Ru(III) species.     

Oxidation of ketones by cerium(IV) in presence of iridium(III) chloride

Kinetic data, in iridium(III) chloride catalyzed oxidation of ethyl methyl ketone (EMK) and methyl propyl ketone (MPK) by cerium(IV) perchlorate in aqueous perchloric acid medium, suggest the formation of complex C₁ between cerium(IV) and organic substrate in the first equilibrium step, which in turn gives rise to another complex C₂ with the catalyst. This second complex in the rate-determining step gives rise to the intermediate products. Interestingly IrCl_3, which is considered to be a sluggish catalyst in alkaline media, was found to surpass the catalytic efficiency of even osmium and ruthenium in acidic media. Rate decreases in the beginning at low acid concentrations, but after reaching to a minimum it becomes directly proportional to acid concentrations. Probably on increasing the acid concentrations hydrolyzed species of ceric perchlorate gradually converts into the un-hydrolyzed species, which then accelerates the rate at higher [H⁺], resulting in the observed peculiar effect of hydrogen ions on the rate. Initial concentrations of cerium(IV) and acid determine the extent of reduction of cerium(IV) by water. Order of the reaction shows direct proportionality with respect to the oxidant and ketones at their low concentrations, but tends to become zeroth order at their higher concentrations. Rate of the reaction shows direct proportionality with respect to [IrCl₃] while change in ionic strength of the medium does not affect the reaction velocity. Parameters such as the energy of activation, free energy of activation and entropy data suggest that methyl propyl ketone forms the activated complex more easily compared to ethyl methyl ketone.     

Synthesis of diols using the hypervalent iodine(III) reagent, phenyliodine(III) bis(trifluoroacetate)

1,2- and 1,3-Bis(trifluoroacetoxy) alcohols are easily obtained from the one-pot reaction of alkenes with phenyliodine(III) bis(trifluoroacetate) (PIFA) in the absence of any additive or catalyst. The products were converted into the corresponding diols by ammonolysis. The use of bicyclic alkenes has shown that rearranged 1,3-diacetoxy alcohols are mostly formed as the major products.     

A family of hexanuclear Mn(III) single-molecule magnets

In an attempt to employ salicylic acid (HOsalH), 2,6-dihydroxy benzoic acid {(HO)₂PhCO₂H}, and naphthalene-1,8-dicarboxylic acid {1,8-naph(CO₂H)₂} in Mn(III) salicylaldoximate chemistry as a means to alter the structural identity of the hexanucluear clusters usually obtained from this reaction system, we have isolated a family of hexanuclear Mn(III) complexes based on salicyladloxime (saoH₂) and 2-hydroxy-1-naphthaldehyde oxime (naphthsaoH₂). Five hexanuclear clusters, [Mn₆O₂(sao)₆(HOsal)₂(EtOH)₄]·EtOH (1·EtOH), [Mn₆O₂(sao)₆{1,8-naph(CO₂Me)(CO₂)}₂(MeOH)₆]·3MeOH (2·3MeOH), [Mn₆O₂(naphthsao)₆{1,8-naph(CO₂Et)(CO₂)}₂(EtOH)₆] (3·2MeOH), [Mn₆O₂(naphthsao)₆(MeCO₂)₂(EtOH)₄]·2H₂O (4·2H₂O), and [Mn₆O₂(naphthsao)₆{(HO)₂PhCO₂}₂(EtOH)₄]·4EtOH (5·4EtOH), have been synthesized and characterized by single-crystal X-ray crystallography. The magnetic properties of 3, 4, and 5 are discussed.     

A bulky oxime for the synthesis of Mn(III) clusters

The reaction between Mn(OAc)₂·4H₂O and Br-saoH₂ (=5-Br-salicylaldoxime) in EtOH in the presence of NMe₄OH led to the formation of the hexanuclear cluster [Mn₆O₂(Br-sao)₆(OAc)₂(H₂O)₂(EtOH)₂]·2.8H₂O·2.2EtOH (1). Switching from Mn(OAc)₂·4H₂O to Mn(ClO₄)₂·6H₂O, the same reaction upon addition of pivH (= trimethyl acetic acid) yielded [Mn₆O₂(Br-sao)₆(piv)₂(H₂O)₂(EtOH)₂]·6EtOH (2 6EtOH), and finally upon changing pivH to NaO₂CPh, we were able to isolate [Mn₆Na₂O₂(Br-sao)₆(O₂CPh)₄(H₂O)₂(EtOH)₄]·6EtOH (3 6EtOH). Clusters 1 and 2 6EtOH describe “typical” [Mn₆/oximate] complexes consisting of two {Mn₃} oxo-centered triangular units bridged by oximate groups, while in 3 6EtOH these triangular motifs are separated by two sodium cations. An investigation into the magnetic properties of all three clusters revealed the presence of dominant antiferromagnetic interactions, leading to ground states of S = 4 and 2 for 1 and 3, respectively. Finally, cluster 2 6EtOH functions as a single-molecule magnet with U_eff = 27.54 K.     

Mn(III)-based reaction of alkenes with quinolinones. Formation of peroxyquinolinones and quinoline-related derivatives

The reactions of 1,1-disubstituted alkenes with 4-hydroxyquinolin-2(1H)-ones under both Mn(III)-catalyzed aerobic oxidation conditions at room temperature and Mn(III)-mediated oxidation conditions at reflux temperature are described. The Mn(III)-catalyzed aerobic oxidation afforded bis(hydroperoxyethyl)quinolinones and azatrioxa[4.4.3]propellanes, while the oxidation with Mn(OAc)₃·2H₂O produced furo[3,2-c]quinolin-4-one analogues. The existence of a substituent at the 3-position of the 4-hydroxyquinolin-2(1H)-ones prevented a double reaction with the alkenes, and (endoperoxy)quinolinones and/or (hydroperoxyethyl)quinolinones were obtained under the Mn(III)-catalyzed aerobic conditions, while furo[3,2-c]quinolinone hemiacetals and vinylquinolinones were selectively produced under the Mn(III)-mediated oxidation conditions depending on the reaction temperature and times. Cyclic assembly of quinolinone-related 1,3-dicarbonyl compounds such as dihydropyridinones, pyranones, and dimedone derivatives was also examined under elevated temperature conditions.     

Mn(III)acetate-mediated additions of active methylene compounds to bicyclic olefins: Synthesis of bicyclic olefin-fused dihydrofurans

Bicyclic alkenes such as benzonorbornadiene, oxabenzonorbornadiene, norbornene, and norbornadiene were reacted with 1,3-cyclohexanedione and ethyl acetoacetate in the presence of Mn(OAc)₃ and Cu(OAc)₂. Except for the reaction of benzonorbornadiene and ethyl acetoacetate, dihydrofuran derivatives were the only products obtained. The formation of naphthalene derivatives was observed together with dihydrofuran in the aforementioned benzonorbornadiene/ethyl acetoacetate reaction. Additionally, the dihydrofuran product from the addition of ethyl acetoacetate to norbornadiene was slowly converted into epoxide derivative with air. The mechanism for the formation of the products is discussed.