Manganese(III) porphyrin supported on multi-wall carbon nanotubes: A highly efficient and reusable biomimetic catalyst for epoxidation of alkenes with sodium periodate

In this paper, the biomimetic epoxidation of alkenes catalyzed by tetrakis(p-aminophenyl)porphyrinatomanganese(III) chloride, [Mn(TNH₂PP)Cl], supported on functionalized multi-wall carbon nanotubes, MWCNT, is reported. The catalyst, [Mn(TNH₂PP)Cl-MWCNT], was used as an efficient and heterogeneous catalyst for epoxidation of alkenes with NaIO₄ at room temperature, in the presence of imidazole as an axial ligand. This new heterogenized catalyst was characterized by elemental analysis, FT IR spectroscopy, diffuse reflectance UV–Vis spectrophotometry, scanning electron microscopy and transmission electron microscopy. The biggest advantage of Mn(TNH₂PP)Cl-MWCNT is its high reusability in the oxidation reactions, in which the catalyst was reused several times without significant loss of its catalytic activity.     

[Mn(TPPS)] immobilized on ionic liquid-modified silica as a heterogeneous and reusable catalyst for epoxidation of alkenes with NaIO<Subscript>4</Subscript> under ultrasonic irradiation

Effective epoxidation of alkenes using sodium periodate was accomplished with Manganese (III) tetrakis(p-sulfonatophenyl)porphyrin, [C₄₄H₂₆N₄O₁₂S₄Na₄], supported on ionic liquids-modified silica, Im-SiO₂, under ultrasonic irradiation conditions is reported. This heterogeneous catalyst, [Mn(TPPS)@SiO₂-Im] was characterized by elemental analysis, scanning electron microscopy (SEM), FT-IR and UV–Vis spectroscopic methods. The synthesized hybrid catalyst was applied for efficient epoxidation of various alkenes with sodium periodate in acetonitrile under ultrasonic irradiation conditions. This solid catalyst can be easily recovered by simple filtration and reused several time without apparent loss of its catalytic activity.     

Epoxidation of alkenes with NaIO<Subscript>4</Subscript> catalyzed by an efficient and reusable natural polymer-supported ruthenium(III) salophen catalyst

In the present study, preparation, characterization, and catalytic activity of Ru(salophen)Cl supported on chitosan were investigated. The prepared heterogeneous catalyst was characterized by diffuse reflectance UV–vis and FT-IR spectroscopic techniques, scanning electron microscopy, and neutron activation analysis. In this catalytic system, the effects of different solvents were studied in the epoxidation of cis-cyclooctene and CH₃CN/H₂O was found to be a better solvent. Also, the effects of oxygen donors such as NaIO₄, H₂O₂, H₂O₂/urea(UHP), tert-BuOOH, NaClO, and Bu₄NIO₄ were studied in the epoxidation of cis-cyclooctene and NaIO₄ was selected as an oxidant. The catalytic activity of this new heterogeneous catalyst in the epoxidation of cyclic and linear alkenes using NaIO₄ as an oxidant in CH₃CN/H₂O at room temperature was studied. The obtained results led us to conclude that [Ru(salophen)Cl@ chitosan] is an efficient catalyst for the epoxidation of alkenes with NaIO₄. The catalyst can be readily recovered simply by filtration and reused several times without any significant loss in its catalytic activity.     

Ni (II) schiff base complex immobilized on graphene oxide nano-sheets catalyzed epoxidation of alkenes

Ni (II) schiff base complex was synthesized by the reaction of nickel acetate tetrahydrate with N, N’-Bis(2,4-di-hydroxybenzaldehyde)-1,2-cyclohexanediamine and supported on modified grapheme oxide nano-sheets using 3-chloropropyltrimethoxysilane as a reactive surface modifier. The heterogeneous nano-catalyst was characterized by Fourier transform infrared spectra, X-ray diffraction, thermogravimetric analysis, transmission electron microscopy, nitrogen adsorption–desorption isotherms and atomic absorption spectroscopy. This catalyst was used for the epoxidation of alkenes using tert-butyl hydroperoxide as oxidant, giving excellent conversions and selectivity. The catalyst showed great reusability and selectivity without significant loss of activity in the epoxidation reactions.     

Highly efficient epoxidation of alkenes with sodium periodate catalyzed by reusable polystyrene-bound ruthenium(III) salophen

In this paper, highly efficient epoxidation of alkenes catalyzed by ruthenium(III) salophen chloride, [Ru(salophen)Cl], supported on functionalized chloromethylated polystyrene, PS, is reported. The PS was modified with 1,4-diaminobenzene, 4-aminophenol and 4-aminothiophenol, and [Ru(salophen)Cl] was attached to the supports via axial ligation. The prepared catalysts were used for efficient epoxidation of alkenes with NaIO₄ at room temperature. These new heterogenized catalysts were characterized by elemental analysis, FT-IR spectroscopy, scanning electron microscopy and transmission electron microscopy. The heterogeneous catalysts were reusable in the oxidation reactions and were reused several times.     

Multi-wall carbon nanotube supported tungsten hexacarbonyl: an efficient and reusable catalyst for epoxidation of alkenes with hydrogen peroxide

Highly efficient epoxidation of alkenes with H₂O₂ catalyzed by tungsten hexacarbonyl supported on multi-wall carbon nanotubes (MWCNTs) modified with 1,2-diaminobenzene is reported. The prepared catalyst, [W(CO)₆@DAB-MWCNT], was characterized by elemental analysis, scanning electron microscopy, FT-IR, and diffuse reflectance UV-Vis spectroscopic methods. The prepared catalyst was applied as an efficient catalyst for green epoxidation of alkenes with hydrogen peroxide in CH₃CN. This heterogeneous metal carbonyl catalyst showed high stability and reusability in epoxidation without loss of its catalytic activity.     

MoO<Subscript>2</Subscript>(acac)<Subscript>2</Subscript> supported on MCM-41: An efficient and reusable catalyst for alkene epoxidation with <Emphasis Type="Italic">tert</Emphasis>-BuOOH

A new heterogeneous catalyst prepared by immobilization of MO₂(acac)₂ on Mobil Catalytic Material, MCM-41, is reported. This catalyst, MoO₂(acac)₂-MCM-41, was successfully applied for efficient epoxidation of olefins with tert-BuOOH in 1,2-dichloroethane as solvent. The catalyst was characterized by elemental analysis, FT-IR, UV-Vis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). This catalyst can be reused several times without significant loss of its catalytic activity.     

Reaction of transsilylation of <Emphasis Type="Italic">N</Emphasis>-methyl-<Emphasis Type="Italic">N</Emphasis>-trimethylsilylacetamide with silanes ClCH<Subscript>2</Subscript>SiR<Superscript>1</Superscript>R<Superscript>2</Superscript>Cl

The reaction of N-methyl-N-trimethylsilylacetamide with silanes ClCH₂SiR¹R²Cl (R¹, R² = H, Me; H, Ph; Ph₂) leads to the formation of (O→Si) chelate compounds with pentacoordinate silicon: N-[chloro(methyl)-silyl]methyl-, N-[chloro(phenyl)silyl]methyl-, and N-[chloro(diphenyl)silyl]methyl-N-methylacetamides. From the data of multinuclear NMR spectroscopy, the intermediates of the reaction of N-methyl-N-trimethylsilylacetamide with ClCH₂SiPhHCl and ClCH₂SiPh²Cl are stable in CDCl₃ solution at room temperature during several days and slowly rearrange to the final (O–Si) chelate compounds.     

Multi-wall carbon nanotube supported manganese(III) porphyrin: an efficient and reusable catalyst for oxidation of 2-imidazolines with sodium periodate

The oxidation of 2-substituted imidazolines with sodium periodate catalyzed by tetrakis(p-aminophenyl)-porphyrinatomanganese(III) chloride, [Mn(TNH₂PP)Cl], supported on functionalized multi-wall carbon nanotubes is reported. A wide variety of 2-imidazolines were efficiently converted to their corresponding imidazoles by this catalytic system. When the same reaction was subjected to ultrasonic irradiation, the reaction times were reduced significantly and the product yields were increased. This catalyst could be reused several times without significant loss of activity. The effects of reaction parameters such catalyst amount, choice of solvent, and the effects of ultrasonic irradiation on the catalytic activity have been investigated.     

[PZnMo2W9O39]5− immobilized on ionic liquid-modified silica as a heterogeneous catalyst for epoxidation of olefins with hydrogen peroxide

The epoxidation of alkenes with hydrogen peroxide catalyzed by [PZnMo₂W₉O₃₉]^5-, ZnPOM, supported on ionic liquid-modified silica, Im-SiO₂, is reported. The immobilized catalyst, [ZnPOM@Im-SiO₂] was characterized by elemental analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), FT-IR and UV–Vis spectroscopic methods. This new synthesized hybrid catalyst was applied for efficient epoxidation of various olefins with aqueous H₂O₂ in acetonitrile under reflux conditions. This solid catalyst can be easily recovered by simple filtration and reused several times without significant loss of its catalytic activity.     

Synthesis,structure and electrochemical properties of some thiosemicarbazone complexes of iridium

Reaction of thiosemicarbazones of salicylaldehyde and 2-hydroxyacetophenone (H₂L¹ and H₂L²) with [Ir(PPh₃)₃Cl] affords complexes of type [Ir(PPh₃)₂(L)(H)] (L = L¹ or L²) in ethanol. A similar reaction carried out in toluene affords the [Ir(PPh₃)₂(L)(H)] complexes along with complexes of type [Ir(PPh₃)₂(L)Cl], where a chloride is coordinated to iridium instead of the hydride. The structure of the [Ir(PPh₃)₂(L²)(H)] and [Ir(PPh₃)₂(L²)Cl] complexes has been determined by X-ray crystallography. Crystal data for [Ir(PPh₃)₂(L²)(H)]: space group, P2₁/c; crystal system, monoclinic; a=12.110(2) Å, b=17.983(4) Å, c=18.437(4) Å, β=103.42(3)°, Z=4; R ₁=0.0591, wR ₂=0.1107. Crystal data for [Ir(PPh₃)₂(L²)Cl]: space group, P2₁/c; crystal system, monoclinic; a=17.9374(11) Å, b=19.2570(10) Å, c=24.9135(16) Å, β=108.145(5)°, Z=4; R ₁=0.0463, wR ₂=0.0901. In all the complexes the thiosemicarbazones are coordinated to the metal center as dianionic tridentate O, N, S-donors and the two triphenylphosphines are trans. The complexes are diamagnetic (low-spin d? ⁶, S=0) and show intense MLCT transitions in the visible region. Cyclic voltammetry on all the [Ir(PPh₃)₂(L)(H)] and [Ir(PPh₃)₂(L)Cl] complexes shows a quasi-reversible Ir(III)–Ir(IV) oxidation within 0.55–0.78 V vs. SCE followed by an irreversible oxidation of the thiosemicarbazone within 0.91–1.27 V vs. SCE. An irreversible reduction of the thiosemicarbazone is also observed within ?1.10 to ?1.23 V vs. SCE.     

Molybdenum hexacarbonyl supported on amine modified multi‐wall carbon nanotubes: an efficient and highly reusable catalyst for epoxidation of alkenes with tert‐butylhydroperoxide

In the present work, highly efficient epoxidation of alkenes catalyzed by Mo(CO)₆ supported on multi‐wall carbon nanotubes modified by 2‐aminopyrazine, APyz‐MWCNTs, is reported. The prepared catalyst was characterized by elemental analysis, scanning electron microscopy, FT IR and diffuses reflectance UV–vis spectroscopic methods. This new heterogenized catalysts, [Mo(CO)₆@APyz‐MWCNT], was used as a highly efficient catalyst for epoxidation of alkenes with tert‐BuOOH. This robust catalyst was reused several times without loss of its catalytic activity. Copyright © 2010 John Wiley & Sons, Ltd.     

Catalytic effects of cationic nanoparticle (CTABr/NaX/H<Subscript>2</Subscript>O,X = Cl,Br) for the piperidinolysis of phenyl salicylate ions

The expression of pseudo-second-order rate constants (k _X) for cationic nanoparticle (CN) [CTABr/NaX/H₂O, X = Br, Cl, CTABr = cetyltrimethylammonium bromide] catalyzed piperidinolysis-ionized phenyl salicylate (PSa^–), at constant [CTABr]_T, 0.1 M piperidine (Pip), and 35°C, were calculated from the relationship: k _obs = (k ₀ + k _X[NaX])/(1 + K ^X/S[NaX]), in which k ₀, k _X, and K ^X/S are constant kinetic parameters and k _obs represents the pseudo-first-order rate constant for Pip reaction with phenyl salicylate ion in the presence of CN. The source of the large catalytic effect of CN catalyst was shown to be due to the transfer of PSa^– from pseudo-phase of the CNs to the bulk aqueous phase through X^–/PSa^– ion exchange at the surface of the CNs.     

Simultaneously improving the tensile and impact properties of isotactic polypropylene with the cooperation of <Emphasis Type="Italic">co</Emphasis>-PP and <Emphasis Type="Italic">β</Emphasis>-nucleating agent through pressure vibration injection molding

In this article, crystalline morphology and molecular orientation of isotactic polypropylene (iPP), random copolymerized polypropylene (co-PP) and β-nucleating agent (β-NA) composites prepared by pressure vibration injection molding (PVIM) have been investigated via polarized light microscopy, scanning electron microscopy, wide-angle X-ray diffraction and differential scanning calorimetry. Results demonstrated that the interaction between co-PP and iPP molecular chains was beneficial for the mechanical improvement and the introduction of β-NA further improved the toughness of iPP. In addition, after applying the pressure vibration injection molding (PVIM) technology, the shear layer thickness increased remarkably and the tensile strength improved consequently. Thus, the strength and toughness of iPP/co-PP/β-NA composites prepared by PVIM were simultaneously improved compared to those of the pure iPP prepared by conventional injection molding (CIM): the impact toughness was increased by five times and tensile strength was increased by 9 MPa. This work provided a new method to further enhance the properties of iPP/co-PP composites through dynamic processing strategy.     

Crystal structure of [Ir(NH<Subscript>3</Subscript>)<Subscript>5</Subscript>Cl]<Subscript>2</Subscript>[OsCl<Subscript>6</Subscript>]Cl<Subscript>2</Subscript>. Crystal-chemical analysis of the iridium-osmium system

The [Ir(NH₃)₅Cl]₂[OsCl₆]Cl₂ binary complex salt has been prepared, and its structure was investigated by single crystal X-ray diffraction. Crystal data: a = 11.1901(13) Å, b = 7.9138(13) Å, c = 13.4384(18) Å; β = 99.640(3)°, V = 1190.0(2), space group C2/m, Z = 2, FW = 1099.47, d _x = 3.068 g/cm³. Thermolysis products of [Ir(NH₃)₅Cl]₂[OsCl₆]Cl₂, [Ir(NH₃)₅Cl][OsBr₆], (NH₄)₂[OsCl₆]_x[IrCl₆]_1?x , and K₂[OsCl₆]_x[IrCl₆]_1?x were studied by X-ray phase analysis; the unit cell parameters were refined, and the dependence of volume per atom (V/Z) on the composition of the Ir Os_1?x solid solution has been plotted.     

Graphene oxide‐bound electron‐deficient tin(IV) porphyrin: a highly efficient and selective catalyst for trimethylsilylation of alcohols and phenols with hexamethyldisilazane

The catalytic activity of graphene oxide‐bound tetrakis(p ‐aminophenyl)porphyrinatotin(IV) trifluoromethanesulfonate, [Sn^IV(TNH₂PP)(OTf)₂], in the trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) is reported. The prepared catalyst was characterized using inductively coupled plasma analysis, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared and diffuse reflectance UV–visible spectroscopies. This heterogeneous catalyst was used for selective trimethylsilylation of various alcohols and phenols with HMDS in short reaction times and high yields. Also, the catalyst is of high reusability and stability, in that it was recovered several times without loss of its initial activity. The chemoselectivity of this catalytic system in the silylation of primary alcohols in the presence of secondary and tertiary alcohols and also phenols was investigated.     

Rhodium(I) bisaldimine complexes in transfer hydrogenation

The reactions of hydrogen transfer from 2-propanol on acetophenone in the presence of the system [Rh(cod)Cl]₂–L] (L is bisaldimine ligands based on (R,R)-1,2-cyclohexanediimine and pyridine-, quinoline-, and thiophenecarboxaldehyde) were studied. Rhodium(I) complexes with optically active ligand showed a high catalytic activity (up to 345 h^–1) and moderate enantioselectivity [up to 55% ee of (R)-1-phenyethanol]. The structure of rhodium complex with N,N'-(1R,2R)-cyclohexane-1,2-diyl-bis[1-(pyridine-2-yl)methanimine] was determined on the basis of the data of ¹H and ¹³C NMR spectroscopy and quantum chemical calculations.     

Ab initio calculations of complexes of tetrachlorides of Group IVA elements: VIII. Structure of SiCl<Subscript>4</Subscript> complexes with hexamethylphosphoric triamide and dynamics of their formation

Quantum-chemical calculations of the systems SiCl₄←OP[N(CH₃)₂]₃ and SiCl₄←2OP[N(CH₃)₂]₃ with complete optimization of their geometry at various Si←O distances were performed by the RHF/6-31G(d) method. The first system was also calculated by the MP2/6-31G(d) method. The calculations of the systems with the complete geometry optimization resulted in trigonal-bipyramidal and trans-octahedral structures, respectively, having energy minima. When the components of the latter system approach each other, first their mutual polarization occurs, and then it is accompanied by electron density transfer from the H and P atoms of the electron-donor molecules to the Cl atoms of the acceptor. The results of the calculation of the trans-octahedral complex agree with the experimental ³⁵Cl NQR data. The electron density of Cl atoms increases upon complex formation, mainly due to an increase in their p _σ electron density.     

One-dimensional heterobimetallic cyanide-bridged Fe(III)–Mn(II) complex: Synthesis,crystal structure,and magnetic properties

A new cyanide-bridged heterobimetallic Fe(III)–Mn(II) complex {[MnL][FebpdBrb]} [FebpdBrb]_n· 2nH₂O has been synthesized by using pyridinecarboxamide trans-dicyanideiron as the building block. The X-ray diffraction analysis has revealed the one-dimensional infinite structure of the complex consisting of the alternating [Mn(L)]²⁺ and [Fe(bpdBrb)(CN)₂]^– units forming a cyanide-bridged cationic polymeric chain, with [Fe(bpdBrb)(CN)₂]^– as the free anions. The antiferromagnetic coupling between the neighboring Fe(III) and Mn(II) ions through the bridging cyanide group has been revealed. The magnetic coupling constant has been determined as of J =–3.17 cm^–1.     

Comparative macrocycle binding of the anticancer drug phenanthriplatin by cucurbit[<Emphasis Type="Italic">n</Emphasis>]urils, β-cyclodextrin and <Emphasis Type="Italic">para</Emphasis>-sulfonatocalix[4]arene: a <Superscript>1</Superscript>H NMR and molecular modelling study

The potential anticancer drug phenanthriplatin, [cis-(NH₃)₂(phenanthridine)Cl]⁺, forms supramolecular complexes with cucurbit[n]urils (CB[n], n?=?7 or 8), β-cyclodextrin and para-sulfonatocalix[4]arene (sCX[4]) as determined by ¹H NMR spectroscopy and molecular modeling. The results show that cucurbit[7]uril binds over the long arm of the drug, where hydrophobic effects and two hydrogen bonds stabilise binding. For cucurbit[8]uril, two phenanthriplatin molecules can bind simultaneously within the macrocycle’s cavity. Unfortunately, Na⁺ was able to displace the drug from both CB[7] and CB[8] making the macrocycles unsuitable as delivery vehicles for phenanthriplatin. Drug binding to β-cyclodextrin occurs at the portal of the macrocycle with no part of the phenanthriplatin located within the cavity. Phenanthriplatin binding to sCX[4] occurs in a 2-to-1, macrocycle-to-drug, ratio with the formation of a capsule-like complex where each sCX[4] binds over opposing ends of the drug. The results indicate that para-sulfonatocalix[4]arene is the only suitable macrocycle of the four studied for further research into phenanthriplatin drug delivery.