Mixed metal oxide catalysts for the selective oxidation of ethylbenzene to acetophenone

MgAl and MgMAl oxides(M = Co,Ni and Cu) with a Mg:M:Al molar ratio = 4:1:1 were synthesized from the calcination of their corresponding layered double hydroxide(LDHs) precursors.Their catalytic activities were examined for the oxidation of ethylbenzene using tert-butylhydroperoxide(TBHP) as an oxidant.The oxidized product was mainly acetophenone.The catalytic activities were in the order of MgCuAl>MgNiAl～NiAl～MgCoAl～CoAl>CuAl>MgAl oxides.Reusability studies show that the catalysts are stable under the re...     

Synthesis, spectral and X-ray structural studies of Ni(II) complexes of N′-acylhydrazine carbodithioic acid esters containing ethylenediamine or o-phenanthroline as coligands

The new complexes [Ni(Hbstbh)₂(en)] (1) and [Ni(Hpchce)(o-phen)₂]Cl·CH₃OH·H₂O (2) with N′-benzoyl hydrazine carbodithioic acid benzyl ester (H₂bstbh) and [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid ethyl ester (H₂pchce) have been synthesized, containing ethylenediamine (en) or o-phenanthroline (o-phen) as coligands. The ligands and their complexes have been characterized by elemental analyses, IR, magnetic susceptibility and single crystal X-ray data. [Ni(Hbstbh)₂(en)] (1) and [Ni(Hpchce)(o-phen)₂]Cl·CH₃OH·H₂O (2) crystallized in the monoclinic and triclinic systems, space group C2/c and P-1, respectively. The (N, O) donor sites of the bidentate ligands chelate the Ni(II) center and form a five-membered CN₂ONi ring. The resulting complexes are paramagnetic and have a distorted octahedral geometry.     

Controlled synthesis of monodispersed AgGaS2 3D nanoflowers and the shape evolution from nanoflowers to colloids

Monodispersed AgGaS₂ three-dimensional (3D) nanoflowers have been successfully synthesized in a “soft-chemical” system with the mixture of 1-octyl alcohol and cyclohexane as reaction medium and oleylamine as surfactant. The crystal phase, morphology and chemical composition of the as-prepared products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution TEM (HTEM), respectively. Results reveal that the as-synthesized AgGaS₂ nanoflowers are in tetragonal structure with 3D flower-like shape. Controlled experiments demonstrated that the shape transformation of AgGaS₂ nanocrystals from 3D nanoflowers (50 nm) to nanoparticles (10-20 nm) could be readily realized by tuning the reaction parameters, e.g., the ratio of octanol to cyclohexane, the length of carbon chain of fatty alcohol, the concentration of oleylamine, etc. The UV-vis and PL spectra of the obtained AgGaS₂ nanoflowers and colloids were researched. In addition, the photoelectron energy conversion (SPV) of AgGaS₂ nanoflowers was further researched by the surface photovoltage spectra.     

A seven membered chelate ring complex of Mn(II) derived from bis(5-phenyl-2H-1,2,4-triazole)-3-yl-disulfane and cleavage of the S-S bond in a Co(II) complex: Synthesis, spectral and structural characterization

The reaction of Mn(OAc)₂·4H₂O with bis(5-phenyl-2H-1,2,4-triazole)-3-yl-disulfane (H₂ptds·2H₂O) (1) yielded new complex [Mn(ptds)(o-phen)₂] (2). It is observed that under similar conditions the reaction of Co(OAc)₂ with H₂ptds·2H₂O (1) leads to thermolysis of the S-S bond of the disulfane to yield [Co(pts)(o-phen)₂]·H₂O·0.5C₂H₅OH, with the newly generated organic ligand 5-phenyl-2H-1,2,4-triazole-3-sulfinate, (pts)²⁻. The ligand H₂ptds·2H₂O (1), [Mn(ptds)(o-phen)₂] (2) and [Co(pts)(o-phen)₂]·H₂O·0.5C₂H₅OH (3) crystallized into monoclinic, trigonal and triclinic crystal systems, respectively. The triazole ring nitrogen of the bidentate ligand chelates the Mn(II) center forming a seven membered chelate ring, while N, O donor sites of the resulting triazole sulfinate bond Co(II) to form a five membered chelate. The resulting complexes are paramagnetic and have a distorted octahedral geometry.     

The determination of the stability constants of mixed ligand complexes of adenine and amino acids with Ni(II) by potentiometric titration method

A potentiometric titration technique has been used to determine the stability constants for the various complexes of Ni(II) with adenine (A) as primary ligand and selected amino acids (L) as secondary ligands. Ternary complexes of amino acids are formed in a stepwise mechanism, whereby (A) binds to Ni(II), followed by interaction with ligand (L), whereas thiol-containing ligands form ternary complexes through a simultaneous mechanism. The formation constants of the complexes were determined at 25 °C and ionic strength 0.1 M NaNO₃. The relative stabilities of the ternary complexes are compared with those of the corresponding binary complexes in terms of Δlog K values. The concentration distribution of the complexes are evaluated.     

Seven-, eight-, and ten-coordinated cerium(III) with highly connective pyridine-2,4,6-tricarboxylate,oxalate, and glycine ligands

Two new 3-D Ce(III) coordination polymers, [Ce_1.3(PTA)₂(Oxa)₂(Gly)(H₂O)₂]·(Gly)4H₂O (1) and [Ce_2.6(PTA)₄(Oxa)₂(H₂O)₁₀]·(MeOH)7H₂O (2) (PTA?=?2,4,6-pyridinetricarboxylate, oxa?=?oxalate and Gly?=?glycine), were synthesized. The oxalate in 1 and 2, generated in situ from the cleavage and chemical rearrangement of PTAH₃, assembled into mixed-ligand networks to generate 3-D frameworks. Single crystal analysis reveals that in both complexes, Ce(III) shows coordination numbers of 7 and 10 in 1 and 8 and 10 in 2. PTA adopts four kinds of coordination modes. These complexes were further characterized using elemental analysis, FTIR spectroscopy and thermogravimetric analysis.     

Structural,infrared spectral and thermogravimetric analysis of a hydrogen-bonded assembly of cobalt(II) and nickel(II) mixed complex cations with hexamethylenetetraamine and aqua ligands: {[M(hmt)2(H2O)4][M(H2O)6]}(SO4)2·6H2O

The synthesized cobalt(II) and nickel(II) complexes {[M(hmt)₂(H₂O)₄][M(H₂O)₆]}(SO₄)₂·6H₂O [M?=?Co(II) (1) and Ni(II) (2), hmt?=?hexamethylenetetraamine] share the same general formula and chemical name {[bis(hexamethylenetetraamine)tetraaquametal(II)][hexaaquametal(II)]} disulfate hexahydrate. Complexes 1 and 2 have been characterized by elemental analysis, infrared spectroscopy, thermal analysis and magnetic moment determination. Each complex has two different cationic complexes co-crystallizing with the sulfate anions. The crystal structure of 1has been determined. Both complex cations in 1 have distorted octahedral geometry and they are linked to the sulfate anions through the coordinated and lattice water molecules. Each sulfate anion is hydrogen bonded to ten water molecules; two of its oxygen atoms have two hydrogen bonds each while the other two oxygen atoms have three hydrogen bonds each. The three uncoordinated nitrogen atoms of hmt in each [Co(hmt)₂(H₂O)₄]²⁺ cation are hydrogen bonded to water molecules of adjacent [Co(H₂O)₆]²⁺ cations. The thermal decomposition of 1 has been investigated further by analyzing the FTIR spectra of the residues formed from each decomposition step, and the data have contributed to establishing the thermal decomposition pathway of both 1and 2.     

Synthesis,crystal structure and fluorescence of a two-dimensional coordination polymer with 1-(pyrazin-2-yl)pyridine-2(1H)-one and thiocyanate as mixed bridge ligands

A two-dimensional sheet coordination polymer, [Cd(μ-C₉H₇N₃O)(μ-NCS)₂] _n , (C₉H₇N₃O=1-(pyrazin-2-yl)pyridin-2(1H)-one), has been synthesized with 1-(pyrazin-2-yl)pyridin-2(1H)-one and thiocyanate anion as bridging ligands, and its crystal structure determined by X-ray crystallography. The crystal belongs to monoclinic system with space group P2₁ /c, and its relevant crystal parameters are: a?=?7.5392(16) Å, b?=?18.343(4) Å, c?=?10.155(2) Å, β?=?106.362(3)°, Z?=?4, V?=?1347.4(5) ų, C₁₁H₇CdN₅OS₂, D _Calcd?=?1.980, R?=?0.0516. The crystal structure reveals that both 1-(pyrazin-2-yl)pyridin-2(1H)-one and thiocyanate anion connect adjacent Cd(II) ions resulting in a two-dimensional sheet structure in the bc plane. There are weak π–π stacking interactions between adjacent pyridine rings. The coordination polymer has weaker fluorescent emission in the solid state than 1-(pyrazin-2-yl)pyridin-2(1H)-one compound, attributed to the π–π stacking interaction and the coordination effect.     

Synthesis and characterization of N,N-diethylnicotinamide-acetylsalicylato complexes of Co(II), Ni(II), Cu(II), and Zn(II)

N,N-diethylnicotinamide-acetylsalicylato complexes of Co(II), Ni(II), Cu(II), and Zn(II) were synthesized and investigated by elemental analysis, magnetic susceptibility, solid state UV–Vis, direct injection probe mass spectra, FTIR spectra and thermoanalytic TG-DTG methods. The complexes contain two waters, two acetylsalicylate (asa) and two N,N-diethylnicotinamide (dena) ligands per formula unit. The acetylsalicylate and N,N-diethylnicotinamide are monodentate through acidic oxygen and nitrogen of pyridine ring. Decomposition of each complex starts with dehydration then decomposition of N,N-diethylnicotinamide and acetylsalicylate, respectively. The thermal dehydration of the complexes takes place in one or two steps. The decomposition mechanism and thermal stability of the investigated complexes are interpreted in terms of their structures. The final decomposition products are found to be metal oxides.