SYNTHESIS OF BIFUNCTIONAL MANGANESE COMPLEXES AND THEIR APPLICATION IN TRANSFER HYDROGENATION OF NITRILES

A series of bifunctional Mn(0), Mn(I), and Mn(II) complexes bearing polydentate ligands with secondary amino functionality were prepared, characterized, and tested as pre-catalysts in transfer hydrogenation of nitriles to amines using ammonia borane as a reducing agent in the presence of 5 mol% of Mn(I) or Mn(II) pre-catalysts, aromatic and aliphatic substrates were converted to either primary or secondary amines 24 h at 80 ⁰C. Primary amine products were isolated as their hydrochloride salts, obtained by the treatment of the reaction mixtures with HCl. Transfer hydrogenation reactions were found to be highly sensitive to the choice of solvent (benzene vs. isopropanol) and the nature of the catalyst used. The superior catalytic activity in transfer hydrogenation of nitriles to primary amines was demonstrated for Mn(I) complexes bearing tridentate PNHN of bidentate PNH ligands. Moreover, high turnovers of nitriles to primary amines have been also demonstrated for the readily accessible phosphine-free NNHO Mn(II) complex. Catalytic reduction reactions were proposed to proceed via a metal-ligand cooperative mechanism and do not require the use of pressurized hydrogen gas and base additives for catalyst activation

Adsorption arsenite from aqueous solutions by Cu/CuO loaded composite track-etched membranes

Nanoscale structures of copper and its oxides are widely used in heterogeneous catalysis and demonstrate improved properties compared to bulk analogues [1]. Previously, we demonstrated the high potential of composite track-etched membranes with copper microtubules (MTs) as effective catalysts for pnitrophenol hydrogenation and the Mannich reaction [2]. In addition, efficient sorption of ions of heavy metals, such as As, Pb, Cd, Ni, etc. is a promising application of CuO NPs [3]. The composites with the internal pore diameter of 280 nm and the copper microtubules wall thickness of 75 nm were obtained by chemical template synthesis in nano-channels of track-etched PET membranes. Upon the analysis of the data on the phase composition and degree of crystallinity of microtubules before and after annealing, it was found that the complete conversion of copper to copper(II) oxide is possible only at temperatures of 140 °C and higher, and 100% tenorite phase is formed after 10 hours of annealing at 140°C. The composites annealed at 140 °C were also tested in terms of their arsenic (III) ions sorption capacities in the flow mode. For the unannealed sample, the effect of flow-rate on sorption activity was studied and the optimal value of 10 mL/min was established. It was shown that the sorption capacity of composite membranes increases by 48.7% compared to the initial sample at 10 h of annealing and then decreases by 24% with an increase in the annealing time (24 h). Successfully combining mechanical strength, the possibility of repeated use, low cost and ease of production, such Cu/CuO/PET membrane composites can be considered as promising materials for sorption of arsenic ions from aqueous solutions