RESUMEN
Colloidal and supported manganese nanoparticles were synthesized following an organometallic approach and applied in the catalytic transfer hydrogenation (CTH) of aldehydes and ketones. Reaction parameters for the preparation of colloidal nanoparticles (NPs) were optimized to yield small (2-2.5â nm) and well-dispersed NPs. Manganese NPs were further immobilized on an imidazolium-based supported ionic phase (SILP) and characterized to evaluate NP size, metal loading, and oxidation states. Oxidation of the Mn NPs by the support was observed resulting in an average formal oxidation state of +2.5. The MnOx@SILP material showed promising performance in the CTH of aldehydes and ketones using 2-propanol as a hydrogen donor, outperforming previously reported Mn NPs-based CTH catalysts in terms of metal loading-normalized turnover numbers. Interestingly, MnOx@SILP were found to lose activity upon air exposure, which correlates with an additional increase in the average oxidation state of Mn as revealed by X-ray absorption spectroscopic studies.
RESUMEN
Metal chloride complexes react with tris(trimethylsilyl)phosphine under mild condition to produce metal phosphide (TMP) nanoparticles (NPs), and chlorotrimethylsilane as a byproduct. The formation of Si-Cl bonds that are stronger than the starting M-Cl bonds acts as a driving force for the reaction. The potential of this strategy is illustrated through the preparation of ruthenium phosphide NPs using [RuCl2 (cymene)] and tris(trimethylsilyl)phosphine at 35 °C. Characterization with a combination of techniques including electron microscopy (EM), X-ray absorption spectroscopy (XAS), and solid-state nuclear magnetic resonance (NMR) spectroscopy, evidences the formation of small (diameter of 1.3 nm) and amorphous NPs with an overall Ru50 P50 composition. Interestingly, these NPs can be easily immobilized on functional support materials, which is of great interest for potential applications in catalysis and electrocatalysis. Mo50 P50 and Co50 P50 NPs can also be synthesized following the same strategy. This approach is simple and versatile and paves the way toward the preparation of a wide range of transition metal phosphide nanoparticles under mild reaction conditions.
RESUMEN
One catalyst, two reaction set-ups, three monomers and unlimited macromolecular microstructural designs: The iron guanidine complex [FeCl2 (TMG5NMe2 asme)] (1) polymerizes lactide faster than the industrially used Sn(Oct)2 and shows high activity towards glycolide and ϵ-caprolactone. Its distinguished features enable the synthesis of both block and random-like copolymers in the melt by a simple change of the polymerization set-up. Sequential addition of monomers yields highly ordered block copolymers including the symmetrical PLA-b-PGA-b-PCL-b-PGA-b-PLA pentablock copolymers, while polymerizations of monomer mixtures feature enhanced transesterifications and pave the way to di- and terpolymers with highly dispersed repeating unit distributions. A robust catalyst active under industrially applicable conditions and producing copolymers with desired microstructures is a major step towards biocompatible polymers with tailor-made properties as alternatives for traditional plastics on the way towards a sustainable, circular material flow.
RESUMEN
A series of phosphonium-based supported ionic liquid phases (SILPs) was prepared for the immobilization of Rh nanoparticles (Rh@SILP). The influence of systematic variations in the structure of the ionic liquid-type molecular modifiers (anion, P-alkyl chain length) on the formation and catalytic properties of Rh nanoparticles (NPs) was investigated. Both the nature of the anion and the length of the P-alkyl chain were found to have a strong impact on the morphology of the NPs, ranging from small (1.2-1.7 nm) and well-dispersed NPs to the formation of large NPs (9.9-16.5 nm) and/or aggregates. The catalytic properties of the resulting Rh@SILP materials were explored using the hydrogenation of benzylideneacetone and biomass-derived furfuralacetone as model reactions. The changes in ring and C=O hydrogenation activity as a function of the SILP structure and the Rh NPs size allowed for the selective synthesis of products with distinct molecular functionalities.
