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Methyltrioxorhenium acts as a catalyst (5 10 Mol ) for the direct electrophilic trifluoromethylation of various aromatic and heteroaromatic compounds using the hypervalent iodine reagent 1 (trifluoromethyl) 12 benziodoxol 3(1H) one (1). The products are formed in up to 77 yield. Mixtures of regioisomers are obtained in the case of substituted and heteroaromatic substrates. The reaction typically carried out in chloroform solvent at 70 degrees C shows a significant induction period. Monitoring by EPR shows the involvement of radical species. A small kinetic deuterium isotope effect of 1.3 is observed for benzene.

We have prepared a series of new rhenium complexes containing chiral ferrocenyldiphosphane ligands of the Josiphos family, starting from commercially available rhenium sources. These new ReV oxido and nitrido complexes, several of which have been characterized by X-ray crystallography, are air- and moisture-stable and are active catalysts in the asymmetric transfer hydrogenation of ketones using 2-propanol as the hydrogen source in the presence of substoichiometric amounts of triethylamine (TEA). The reaction proceeds cleanly with good to excellent yields (50–99 %) but with moderate enantioselectivity (up to 58 % ee). A mechanism not involving hydridic species is proposed.

The paramagnetic Re(III) complex [ReCl3(Pigiphos)] (1) ((R)-(S)-Pigiphos = bis{(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyl}cyclohexylphosphine) is accessible from [ReCl3(NCMe)(PPh3)2] and the ligand Pigiphos. 1 reacts with an excess of NaBH4, affording the polyhydride complex [ReH5(Pigiphos)] (2), which was shown to be a classic polyhydride (NMR T1(min) = 158 ms). This complex reacts readily with both Bronsted acids and hydride scavengers to give the corresponding cationic tetrahydride species, which was shown to be active in the catalytic hydrogenation of dimethyl itaconate.

New polynuclear zinc complexes containing tridentate Schiff base ligands were successfully synthesized and fully characterized. The solid-state structure of the complexes was determined using single crystal X-ray diffraction. The complexes display a tetranuclear cubane-like core structure [Zn4O4] and sowed good catalytic activity towards the ring-opening polymerization (ROP) of rac-lactide (rac-LA) and ɛ-caprolactone (ɛ-CL) under solvent-free conditions. The polylactic acid (PLA) obtained from rac-LA showed isotactic enrichment, as proved by homonuclear decoupled 1H NMR analysis. These complexes also showed good activity and superior control towards the ROP of rac-LA and ɛ-CL in the presence of benzyl alcohol as a co-initiator. Furthermore, Kinetic studies demonstrated that the ROP of rac-LA and ɛ-CL has a first order dependence on both monomer (rac-LA and ɛ-CL) and catalyst concentration. This article is protected by copyright. All rights reserved.

The provision of energy has been listed in the “Top Ten of global concerns” as the single most important issue to be faced to improve quality of life and ultimately to stop, or at least to mitigate, the environmental impact of human activities on the planet. [1] One way in which chemistry can be used to provide more sustainable and benign energy technologies is through the development of artificial photosynthesis systems, which allow for the conversion of the energy of sunlight into useful chemical energy by water splitting. [2] The resulting molecular hydrogen constitutes in principle a clean, renewable, and carbon-free energy source. [3]

Este texto presenta la implementación del proyecto de Prácticas Evaluativas y Pruebas “Saber” en laInstitución Educativa San Judas Tadeo del municipio de Bello (Antioquia). En el proyecto se proponeun modelo de intervención a partir de la experiencia con docentes y estudiantes sobre lineamientos ytécnicas para la elaboración de preguntas tipo prueba “Saber”. La sistematización de esta experienciaaporta a la producción de conocimiento sobre las prácticas evaluativas, a través de su reconstrucciónordenada, coherente y jerarquizada, con el fin de involucrar a docentes y estudiantes en la elaboraciónde preguntas como estrategia didáctica, para el incremento de aciertos en los resultados en las pruebas“Saber”.

In this chapter, two industrial processes of gas-phase, hydrocarbon catalytic oxidation are examined: (a) the oxychlorination of ethylene to 1,2-dichloroethane; and (b) the oxidation of n-butane to maleic anhydride. In the former case, the use of ethane as an alternative reactant has been studied, still without success, whereas in the latter case the alkane has replaced the corresponding C4 alkenes because of the better selectivity achieved. Recent developments are discussed for the two reactions, especially in terms of catalysts’ chemical-–physical and reactivity properties.