Andrés Suárez

Nitrous oxide (N ₂ O) is a significant contributor to climate change owing to its dual role as greenhouse gas and ozone-depleting molecule. Herein, the catalytic reduction of N ₂ O to N ₂ using methanol (MeOH) as a terminal reductant was investigated employing a series of Ru complexes supported by proton-responsive picoline- and lutidine-derived pincer ligands incorporating N-heterocyclic carbene donors (CNC and CNN). Among the complexes examined, a Ru catalyst featuring a picoline-derived CNN ligand incorporating a secondary amine functionality displayed the highest activity, achieving turnover numbers (TONs) up to 417 after 72 h, in the reduction of N ₂ O to N ₂ . Under catalytic conditions, the formation of metal nanoparticles from this catalytic precursor was observed. These nanoparticles were independently synthesized and found to be catalytically active in the reduction of N ₂ O with MeOH. Finally, control experiments further demonstrated that both homogeneous and nanoparticle species contribute to the overall catalytic process, participating in the methanol reforming and N ₂ O reduction steps.

A manganese( i ) complex featuring a CNN pincer ligand incorporating two acidic sites serves as catalyst for ester hydrogenation.

Reaction of ligand N -phenyl-2,2-bis(3,5-dimethylpyrazol-1-yl)thioacetamide (pbptamH) with MCl ₂ (M = Pd, Pt) in acetonitrile results in the formation of cationic complexes 1a-b with the general formula [(pbptamH) ₂ M]Cl ₂ .

Los diodos orgánicos emisores de luz (OLED) son una tecnología de vanguardia utilizada en pantallas de celulares inteligentes, televisores, computadoras portátiles y otros dispositivos. A diferencia de las pantallas LCD, los OLED emiten luz de forma independiente en cada píxel, lo que permite negros más profundos, colores más vibrantes y una mayor eficiencia energética. Desde su creación en 1987 por Kodak, los OLED han evolucionado a través de tres generaciones clave: Fluorescentes (baja eficiencia), fosforescentes (utilizan metales pesados para mayor eficiencia) y fluorescencia térmicamente activada retardada (TADF, libre de metales y amigable con el medio ambiente). Cada generación ha mejorado la eficiencia cuántica externa (EQE) y la precisión del color, aunque persisten desafíos como la estabilidad de los emisores azules. Avances recientes, como la hiperfluorescencia, sugieren el surgimiento de una cuarta generación. Los OLED ejemplifican la sinergia entre la química y la ingeniería, ofreciendo un rendimiento de la pantalla superior, al mismo tiempo que abordan preocupaciones sobre la sostenibilidad.

El proceso Wacker-Smidt plantea la síntesis del acetaldehído el cual es ampliamente estudiado en síntesis orgánica debido a sus propiedades, usos industriales y síntesis de sustancias químicas que son empleadas en perfumería, tintes y sabores sintéticos principalmente. El proceso ocurre mediante el uso de sales de paladio (II) y cobre (II) como catalizadores en medio acuoso, siendo uno de los más importantes a escala industrial por su catálisis con metales de transición, empleando un proceso organometálico para la recuperación del metal.

A manganese(I) complex featuring a picoline-derived CNN pincer ligand with two acidic sites ‒the methylene linker and a secondary amino group‒ has been synthesized. In the presence of an alkoxide base, this complex catalyzes the hydrogenation of esters to the corresponding alcohols under relatively mild conditions (1.0 mol% Mn, 10 mol% KOR, 20 bar H2, 110 oC). Stoichiometric reactions of the Mn(I) precursor with an excess of strong base (3 equiv of KHMDS or KOtBu) yield a manganate(I) species (Mn-CNN**) via the deprotonation of both acidic sites of the pincer ligand. X-ray photoelectron spectroscopy (XPS) evinces that the Mn-CNN** complex features a Mn center coordinated by a dianionic CNN** ligand. Finally, detailed DFT calculations were carried out on the two key steps of the catalytic cycle ‒H2 activation and hydride transfer to the ester substrate‒ considering neutral and anionic manganese species. The results indicate that ester hydrogenation proceeds via a Mn(I)-mediated anionic–dianionic manifold, where ligand deprotonation facilitates both H2 cleavage and hydride transfer.

H/D exchange in N-heterocycles with D ₂ gas was investigated using ultrasmall Ru/Co nanoparticles stabilized by NHC ligands. Catalytic performance is governed by both nanoparticle composition and substrate nature.

Air-stable ruthenium­(II) complexes based on a picoline-derived CNC pincer ligand, [RuH­(CNC)­(CO)L]X (L = PPh₃, X = Br; L = CO, X = BF₄), were found to catalyze under basic conditions the oxidation with N₂O of a series of alcohols to carboxylates. Both [RuH­(CNC)­(CO)L]X complexes react readily with strong bases (tBuOK or KHMDS), giving rise to a Ru­(II) complex containing a deprotonated CNC* ligand (when L = PPh₃) or a Ru(0)-CNC derivative (for L = CO). Furthermore, the mechanism of the catalytic reaction has been elucidated through density functional theory (DFT) calculations. The catalytic cycle has been shown to proceed through an outer-sphere mechanism comprising four key transformations, which involve Ru­(II) intermediates based on the deprotonated CNC* ligand: (i) alkoxide dehydrogenation to yield a Ru­(II) hydride complex and an aldehyde molecule, (ii) N₂O insertion into the ruthenium–hydride bond to yield a hydroxy ruthenium species and N₂, (iii) nucleophilic attack of the hydroxo ligand in the Ru–OH complex to the intermediate aldehyde, and (iv) dehydrogenation of the formed alcoholate to regenerate the catalytically active Ru­(II) hydride and produce the carboxylate product.

Nickel nanoparticles (Ni·MIC) stabilized with mesoionic 1,2,3-triazolylidene (MIC) ligands were prepared via decomposition of the [Ni(COD)₂] (COD = 1,5-cyclooctadiene) complex with H₂ (3 bar) in the presence of 0.2 or 0.5 equiv of ligand. The obtained monodisperse and small-sized (3.2-3.8 nm) nanoparticles were characterized by high-resolution transmission electron microscopy (TEM, HRTEM) and inductively coupled plasma (ICP) analysis. Further analysis of the nickel nanoparticles by X-ray photoelectron spectroscopy (XPS) demonstrated the coordination of the MIC ligands to the metal surface. Finally, the Ni·MIC nanoparticles were applied in the isotopic H/D exchange in hydrides of group 14 elements (Si, Ge, Sn) using D₂ gas under relatively mild conditions (1.0-1.8 mol % Ni, 1 bar D₂, 55 °C). High and chemoselective deuterium incorporation at the E-H (E = Si, Ge, Sn) bond in these derivatives was observed.

Picoline-derived Ni–CNP hydride complexes activate N₂O upon base activation, and catalyse the reduction of N₂O with pinacolborane.