Investigation of the solvent free isomerisation of cis-Mo(CO)4L2 [L = PPh2Et, PPh3, PPh2Me, and P(m-tolyl)3] by diffuse reflectance infrared Fourier transform

Thermal analysis of cis-Mo(CO)4L2 [L= PPh2Et, PPh3, PPh2Me and P(m-tolyl)3] revealed that they undergo cis to trans isomerisation under solventless conditions. For L = PPh3 and P(m-tolyl)3, the reaction occurred in the solid state. For L = PPh2Et and PPh2Me the reaction occurred in the melt and was followed by trans isomer solidification. The rate of the solid state isomerisation of cis-Mo(CO)4 (PPh3)2 was investigated by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and the results showed that the reaction was first order. A thermomicroscopic investigation of cis-Mo(CO)4[P(m-tolyl)3]2 revealed that the isomerisation was surface-initiated.KEY WORDS: Solventless reactions, Molybdenum, Isomerisation, Thermal analysis Bull. Chem. Soc. Ethiop. 2011, 25(2), 209-220

Synthesis and X-ray studies of ruthenium(II) complexes containing hydrazine and benzyl isocyanide ligands

The reaction of the polymeric species [{RuCl2(COD)}x] (1; x > 2; COD = cyclo-octa-1,5-diene) and hydrazine hydrate in methanol under reflux gave a pale pink solution from which the salt [Ru(COD)(N2H4)4][BPh4]2.CH3OH (2) was isolated on addition of NaBPh4. Treatment of 2 in refluxing acetone in the presence of the ligand benzyl isocyanide give a complex of stoichiometry [Ru(NH2N=CMe2)2(PhCH2NC)4][BPh4]2 (3) on the substitution of the labile COD ligand. The two compounds have been characterized by elemental analyses, IR and NMR measurements and single-crystal X-ray diffraction studies. The ruthenium in both compounds has a distorted octahedral coordination geometry. KEY WORDS: Cycloocta-1,5-diene, Hydrazine hydrate, Isocyanide, Ruthenium Bull. Chem. Soc. Ethiop. 2013, 27(3), 405-411.DOI: http://dx.doi.org/10.4314/bcse.v27i3.

<b>Investigation of the solvent free isomerisation of <i>cis</i>-Mo(CO)₄L₂ [L = PPh₂Et, PPh₃, PPh₂Me, and P(<i>m</i>-tolyl)₃] by diffuse reflectance infrared Fourier transform spectroscopy and thermal methods</b>

Thermal analysis of <i>cis</i>-Mo(CO)₄L₂ [L= PPh₂Et, PPh₃, PPh₂Me and P(<i>m</i>-tolyl)₃] revealed that they undergo <i>cis</i> to <i>trans</i> isomerisation under solventless conditions. For L = PPh₃ and P(<i>m</i>-tolyl)₃, the reaction occurred in the solid state. For L = PPh₂Et and PPh₂Me the reaction occurred in the melt and was followed by <i>trans</i> isomer solidification. The rate of the solid state isomerisation of <i>cis</i>-Mo(CO)₄ (PPh₃)₂ was investigated by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and the results showed that the reaction was first order. A thermomicroscopic investigation of <i>cis</i>-Mo(CO)4[P(<i>m</i>-tolyl)₃]₂ revealed that the isomerisation was surface-initiated

Microwave radiation in the modification of iron Fischer-Tropsch catalysts

Potassium-promoted unsupported iron Fischer–Tropsch catalysts have been subjected to microwave radiation treatment as part of the catalyst preparation process. The treatment is applied after the catalysts have been dried and calcined. Solid-state modifications occur which result in changes in the manner and quantity of carbon monoxide adsorbed on the surface as detected by temperature programmed surface reaction (TPSR) with hydrogen. Methane is the essential product of the TPSR runs. The response to microwave treatment is an increase in the methane production at all potassium levels, but the magnitude of the increase is potassium-loading dependent and peaks at a potassium loading of 0.7 wt%. Microwave-induced changes in TPSR characteristics appear to result from selective heating occurring almost immediately on exposure of the catalysts to radiation. Longer duration of microwave exposure does not appear to result in further changes

Synthesis and study of carbon microspheres for use as catalyst support for cobalt

The production of pure carbon spheres was achieved in the absence of a catalyst through the direct pyrolysis of two hydrocarbon sources, acetylene and ethylene. Systematic studies using acetylene as the feedstock indicated that the size distribution of the resulting carbon microspheres can be controlled by pyrolysis temperature, time and feedstock flow rate. The resulting spheres were fully characterised by transmission electron microscopy (TEM) and thermogravimetric analysis. The TEM examination showed that these spheres have a ball-like and chain-like morphology, and the balls have smooth surfaces with a variation in diameter size and distribution determined by the reaction conditions. Carbon microsphere-supported cobalt catalysts were synthesised and have shown good activity in the ethylene hydrogenation reaction

Synthesis and study of carbon microspheres for use as catalyst support for cobalt

The production of pure carbon spheres was achieved in the absence of a catalyst through the direct pyrolysis of two hydrocarbon sources, acetylene and ethylene. Systematic studies using acetylene as the feedstock indicated that the size distribution of the resulting carbon microspheres can be controlled by pyrolysis temperature, time and feedstock flow rate. The resulting spheres were fully characterised by transmission electron microscopy (TEM) and thermogravimetric analysis. The TEM examination showed that these spheres have a ball-like and chain-like morphology, and the balls have smooth surfaces with a variation in diameter size and distribution determined by the reaction conditions. Carbon microsphere-supported cobalt catalysts were synthesised and have shown good activity in the ethylene hydrogenation reaction

Generation of radical species in CVD grown pristine and N-doped solid carbon spheres using H2 and Ar as carrier gases

Solid carbon spheres (CSs, d ≈ 200 nm) were synthesized (yield, <40%) in a vertically oriented chemical vapor deposition (CVD) reactor using acetylene as a carbon source and Ar or H2 as the carrier gas. The CSs synthesized in the presence of H2 exhibited a broader thermal gravimetric derivative curve and a narrower paramagnetic signal than the CSs synthesized in Ar. Post synthesis doping of both types of CSs with nitrogen was achieved by passing acetonitrile at 800 °C for 1 h over the CSs in a CVD reactor. The N-doped CSs (NCSs) synthesized under both H2 and Ar displayed an increase in ID/IG ratios as obtained from Raman spectroscopy and showed an increase in the paramagnetic signal due to the presence of nitrogen induced defects compared to the undoped CSs. The NCSs synthesized in H2 had less graphitic-N (22%) than those produced in Ar (50%). The presence of a higher percentage of pyridinic-N and pyrrolic-N for the NCSs prepared with H2 as carrier gas suggested H2 etching effects on the CSs. Further, the N-doped carbon spheres obtained in the presence of H2 gave a higher N/C ratio (5.0) than in the presence of Ar (3.7). The introduction of edge defects and paramagnetic centers in CSs in the presence of H2 gas without the aid of a metal catalyst opens up a platform for regulating surface and catalytic reactions of CSsEM201

Composites of polyvinyl alcohol and carbon (coils, undoped and nitrogen doped multiwalled carbon nanotubes) as ethanol, methanol and toluene vapor sensors

We investigate the chemical sensing behavior of composites prepared with polyvinyl alcohol and carbon materials (undoped multiwalled carbon nanotubes, nitrogen-doped multiwalled carbon nanotubes and carbon nanocoils). We determine the sensitivity of thin films of these composites for ethanol, methanol and toluene vapor, comparing their conductance and capacitance responses. The composite that exhibits highest sensitivity depends on specific vapor, vapor concentration and measured electrical response, showing that the interactivity of the carbon structure with chemical species depend on structural specificities of the carbon structure and doping. © 2011 American Scientific Publishers. All rights reserved

Synthesis Of C 60-containing Polymers By Ring-opening Metathesis Co-polymerization Of A C 60-cyclopentadiene Cycloadduct And N-(cycloheptyl)-endo-norbornene-5, 6-dicarboximide And Their Application In A Photovoltaic Device

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