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The density functional theory (DFT) method was used to investigate the mechanism of N-arylation of nitrogen heterocycles with aryl halides catalyzed by CoCl 2 ·6H 2 O in the presence of different chelating ligands. Cobalt complexes of N, Nˊ -dimethylethenediamine ligand were selected as model catalytic system. Calculations were carried out for single electron transfer, oxidative addition/reductive elimination, iodine atom transfer and σ-bond metathesis mechanism for different possible intermediate cobalt complexes in the reaction solution. According to calculation results, the single electron transfer mechanism has the lowest activation energy (23.3 kcal/mol) for the C-N coupling reaction. Iodine atom transfer mechanism shows 25.6 kcal/mol activation energy for the reaction. Activation energy for oxidative addition/reductive elimination (49.2 kcal/mol) and σ-bond metathesis mechanism (45.5 kcal/mol) is very high under the given experimental conditions. [ABSTRACT FROM AUTHOR]

The density functional theory (DFT) method was used to investigate the mechanism of ligand-free copper-catalyzed arylation of nitrogen heterocycles from benzenediazonium acetate. Two possible mechanisms, single electron transfer and oxidative addition/reductive elimination reaction mechanism were investigated for two possible Cu(I) complexes in the reaction solution. Complex 1 has an acetate and a pyrazole ligand coordinated to Cu(I), and complex 2 has two pyrazole ligands coordinated to Cu(I). Both Cu(I) complexes have sufficiently low activation energy barriers for oxidative addition/reductive elimination reactions. Activation energy barrier for single electron transfer reaction is significantly higher than oxidative addition/reductive elimination reaction. [ABSTRACT FROM AUTHOR]

The effect of ZrO 2 crystalline phases on Pd/ZrO 2 for catalytic combustion of toluene was investigated. It was found that Pd/t-ZrO 2 showed superior activity when the toluene concentration was lower than 2000 ppm, while Pd/m-ZrO 2 performed better with toluene concentration higher than 3000 ppm. Kinetic studies showed that the reaction order of toluene on Pd/t-ZrO 2 and Pd/m-ZrO 2 is 0 and 2, respectively. The catalytic activity was controlled by combined effect of PdO activity and quantity, which was correlated with the interaction between palladium and zirconia. The t-ZrO 2 increased PdO species activity, while m-ZrO 2 could enhance the amount of PdO. DFT results showed that the p-band center of the O of PdO on t-ZrO 2 was higher, suggesting that PdO was more active. In situ -DRIFTS revealed that the reaction pathway of catalytic oxidation of toluene on Pd/ZrO 2 was as follows: toluene was oxidized stepwise to benzyl alcohol, benzaldehyde, benzoic acid, CO 2 and H 2 O. [Display omitted] • Effect of Pd/ZrO 2 with different ZrO 2 crystal types for toluene combustion. • Catalytic activity was controlled by the comprehensive effect between PdO activity and PdO quantity. • The reaction order of toluene on Pd/t-ZrO 2 and Pd/m-ZrO 2 is 0 and 2, respectively. • Desorption energies of O atoms in O-Pd/m-ZrO 2 and O-P/t-ZrO 2. • The reaction pathway of catalytic combustion of toluene on Pd/ZrO 2 catalysts. [ABSTRACT FROM AUTHOR]