A comparative homocoupling reaction of aryl halides using monomeric orthopalladated complex of 4‐methoxybenzoylmethylenetri‐ phenylphosphorane under conventional and microwave irradiation conditions

The activity of [Pd(C₆H₄CH₂NH₂‐κ²‐C‐N)PPh₃MOBPPY]OTf complex, A (MOBPPY = 4‐methoxybenzoylmethylenetriphenylphosphoraneylide) was investigated in the homocoupling reaction of a vast range of aryl halides under both conventional and microwave irradiation conditions and their results were compared. The complex was active and showed high efficiency in the formation of new C‐C bonds. The yields were excellent using a catalytic amount of [Pd(C₆H₄CH₂NH₂‐κ²‐C‐N)PPh₃MOBPPY]OTf complex in N, N‐dimethylformamide at 120 °C. In comparison to conventional heating conditions, the reactions under microwave irradiation gave higher yields in shorter reaction times. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis,spectroscopic and structural characterization of orthopalladated complexes with 4-phenylbenzoylmethylene triphenyl phosphorane ylide

The orthometalated complex [Pd(μ-Cl)(C₆H₅C₆H₄C(O)CHPPh₂C₆H₄-κ²-C,C)]₂ (1) was prepared by refluxing in MeOH/CH₂Cl₂ equimolecular amounts of Pd(OAc)₂ and (Ph)₃PCHCOC₆H₄-Ph-4 (=PhBPPY) followed by addition of excess NaCl. Complex 1 reacts with 4-picoline to give the mononuclear derivative [Pd(PhC₆H₄COCHPPh₂C₆H₄)(4-picoline)] (2) whose crystal structure has been determined by X-ray diffraction. The precursor complex (1) could not be isolated in a pure form, but it can be used as a starting material for the synthesis of derivatives of mononuclear cyclo-palladated complexes. Orthometallation and ylide C-coordination in complexes 3–5 were characterized by elemental analysis as well as various spectroscopic techniques.     

Investigation of nanostructural,thermal and magnetic properties of yttrium iron garnet synthesized by mechanochemical method

This paper focuses on the magnetic, structural and thermal properties of mechanically alloyed Y₂O₃/α-Fe₂O₃ mixed powders and investigates the effects of the mechanical milling and heat treatment on the synthesis of yttrium iron garnet from the primary materials. The morphological and structural studies were carried out by scanning electron microscope and X-ray diffraction, respectively. The thermal activities were measured by differential thermal analysis. The magnetic properties were studied by vibrating sample magnetometer. The results showed that high-energy milling does not lead to the garnet formation and even does not decrease the temperature of the garnet formation. Furthermore, the orthoferrite phase can be achieved slightly during the milling process (up to 96 h) and completely by the heat treatment at lower temperatures (850 °C).     

A green protocol for the N-formylation of amines using molybdate sulfuric acid as a reusable solid catalyst

A novel and efficient method for the N-formylation of amines via the reaction of orthoformates and amines is developed. The reactions are mediated by a catalytic amount of molybdate sulfuric acid as a heterogeneous solid acid.     

Palladium‐catalyzed cyanation reaction of aryl halides using K4[Fe(CN)6] as non‐toxic source of cyanide under microwave irradiation

An efficient method for preparation of aryl nitriles—using [Pd{C₆H₂(CH₂CH₂ NH₂)‐(OMe)₂,3,4} (µ‐Br)]₂ complex as an efficient catalyst and K₄[Fe(CN)₆] as a green cyanide source—from aryl bromides, aryl iodides and aryl chlorides under microwave irradiation has been reported. This complex has been demonstrated to be an active and efficient catalyst for this reaction. Using a catalytic amount of this synthesized palladium complex in DMF at 130 °C led to production of the cyanoarenes in excellent yields in short reaction times. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and Characterization of Iron Oxide Nanoparticles by Solid State Chemical Reaction Method

The iron oxide nanoparticles were synthesized by solid state chemical reaction method. The synthesized powders were characterized by XRD, SEM, EDAX and TG-DTA techniques. An average grain size of 10–20 nm for Maghemite and 80–85 nm for Hematite was calculated using XRD line broadening and SEM. The effect of different parameters such as annealing temperature, milling time, Fe⁺³:Fe⁺² concentration ratio have been investigated on the particle size and phase formation. Heat treatment of the produced powders in which Fe⁺³:Fe⁺² ratio equal to 2:1, resulted in tetragonal (Maghemite) and rombohedral (Hematite) structures at 300 and 600 °C, respectively. It was found that by changing Fe⁺³:Fe⁺² ratios from 2:1 to 1:2, hematite phase and from 2:1 to 1:1, Maghemite phase were formed at 300 °C. In addition with increasing milling time, the iron oxide particle size decreases, but there was no changing in the kind of phase.     

Synthesis of TiO<Subscript>2</Subscript> nano powder by the sol-gel method and its use as a photocatalyst

In this work the titanium dioxide powder was prepared by the optimized and simple Sol-Gel method and then characterized. The gelling pH was set to values of 3 (TiO₂-A), 7 (TiO₂-N) and 9 (TiO₂-B) to observe the effect on the properties of the material. In these three cases nanoparticulated materials were obtained with particle sizes between 10nm and 20nm. The larger surface areas were obtained at pH 3, which is several times larger than the others. Furthermore, with the gelling condition pH 3, it was possible to synthesize pure anatase phase titania. Some preliminary results on the test of the photocatalytic activity of the synthesized materials in the reduction of nitric oxide are presented. Based on these results the nanoparticle TiO2, which was prepared in acidic pH 3 with the pure anatase phase and the lowest particle size has the highest reactivity for the photocatalytic reduction of nitric oxide.     

Electrocatalytic Reduction of Dioxygen on the Surface of Glassy Carbon Electrodes Modified with Cobalt Porphyrin Complexes

The preparation and electrocatalytic behavior of glassy carbon electrodes modified with three different cobalt porphyrin complexes were investigated. The electrocatalytic ability of the modified electrodes for the reduction of dioxygen to hydrogen peroxide and water in air‐saturated aqueous solutions was examined by cyclic voltammetry and chronoamperometry techniques. The porphyrin‐adsorbed glassy carbon electrodes possess excellent electrocatalytic abilities for dioxygen reduction with overpotential about 0.5 V lower than that at a plain glassy carbon electrode. The experimental parameters were optimized and the mechanism of the catalytic process was discussed. The possible effects of the electron‐donating properties of groups in the meso‐position of the porphyrin ring were investigated.     

Impact of Coffee Bean Roasting on the Content of Pyridines Determined by Analysis of Volatile Organic Compounds

The aim of the study was to analyze the process of roasting coffee beans in a convection–conduction roaster (CC) without a heat exchanger and a convection–conduction–radiation roaster (CCR) with a heat exchanger for determination of the aroma profile. The aroma profile was analyzed using the SPME/GC-MS technique, and an Agrinose electronic nose was used to determine the aroma profile intensity. Arabica coffee beans from five regions of the world, namely, Peru, Costa Rica, Ethiopia, Guatemala, and Brazil, were the research material. The chemometric analyses revealed the dominance of azines, alcohols, aldehydes, hydrazides, and acids in the coffee aroma profile. Their share distinguished the aroma profiles depending on the country of origin of the coffee beans. The high content of pyridine from the azine group was characteristic for the coffee roasting process in the convection–conduction roaster without a heat exchanger, which was shown by the PCA analysis. The increased content of pyridine resulted from the appearance of coal tar, especially in the CC roaster. Pyridine has an unpleasant and bitter plant-like odor, and its excess is detrimental to the human organism. The dominant and elevated content of pyridine is a defect of the coffee roasting process in the CC roaster compared to the process carried out in the CCR machine. The results obtained with the Agrinose showed that the CC roasting method had a significant effect on the sensor responses. The effect of coal tar on the coffee beans resulted in an undesirable aroma profile characterized by increased amounts of aromatic volatile compounds and higher responses of Agrinose sensors.     

Orthopalladation of phosphorus ylides in endo position with bidentate ligands

The ortho-metallated complexes [Pd₂{κ²(C,C)-C₆H₄(PPh₂CHC(O)C₆H₅R}₂(μ-Cl)₂] (R = Ph (1a), NO₂ (1b), Br (1c)) were prepared by refluxing equimolar mixtures of Ph₃PCHC(O)C₆H₅R, (R = Ph, NO₂, Br) and Pd(OAc)₂ in MeOH, followed by an excess of NaCl. The dinuclear complexes (1a-1c) react with silver trifluoromethylsulfonate and bidentate ligands [L = bipy (2,2′-bipyridine), phen (phenanthroline), dppe (bis(diphenylphosphino)ethane), dppp (bis(diphenylphosphino)propane)] giving the mononuclear stabilized orthopalladated complexes in endo position [Pd{κ²(C,C)-C₆H₄(PPh₂CHC(O)R}L](OTf) [R = Ph, L = phen (2a), bipy (3a), dppe (4a), dppp (5a); R = NO₂, L = phen (2b), bipy (3b), dppe (4b), dppp (5b); R = Br, L = phen (2c), bipy (3c), dppe (4c), dppp (5c); OTf = trifluoromethylsulfonate anion]. Orthometalation and ylidic C-coordination are demonstrated by an X-ray diffraction study of 2c and 3c. In the structures, the palladium atom shows a slightly distorted square-planar coordination geometry.