Artículos (Química Inorgánica)

URI permanente para esta colecciónhttps://hdl.handle.net/11441/10919

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In-situ DRIFTS steady-state study of CO2 and CO methanation over Ni-promoted catalysts
(Elsevier, 2023-04-15) González Castaño, Míriam; González Arias, Judith; Bobadilla Baladrón, Luis Francisco; Ruiz-López, E.; Odriozola Gordón, José Antonio; Arellano-García, H.; Química Inorgánica; Ingeniería Química y Ambiental; European Union (UE)
Promoting the performance of catalytic systems by incorporating small amount of alkali has been proved effective for several reactions whilst controversial outcomes are reported for the synthetic natural gas production. This work studies a series of Ni catalysts for CO2 and CO methanation reactions. In-situ DRIFTS spectroscopy evidenced similar reaction intermediates for all evaluated systems and it is proposed a reaction mechanism based on: i) formate decomposition and ii) hydrogenation of lineal carbonyl species to methane. Compared to bare Ni, the enhanced CO2 methanation rates attained by NiFe/Al and NiFeK/Al systems are associated to promoted formates decomposition into lineal carbonyl species. Also for CO methanation, the differences in the catalysts’ performances were associated to the relative concentration of lineal carbonyl species. Under CO methanation conditions and opposing the CO2 methanation results where the incorporation of K delivered promoted catalytic behaviours, worsened CO methanation rates were discerned for the NiFeK/Al system.
3D-printed structured catalysts for CO2 methanation reaction: Advancing of gyroid-based geometries
(Elsevier, 2022-04-15) González Castaño, Míriam; Baena-Moreno, Francisco M.; Navarro de Miguel, Juan Carlos; Miah, Kamal U.M.; Arroyo Torralvo, Fátima; Ossenbrink, Ralf; Odriozola Gordón, José Antonio; Benzinger, Walther; Hensel, Andreas; Wenka, Achim; Arellano-García, Harvey; Química Inorgánica; Ingeniería Química y Ambiental; Universidad de Sevilla
This work investigates the CO2 methanation rate of structured catalysts by tuning the geometry of 3D-printed metal Fluid Guiding Elements (FGEs) structures based on periodically variable pseudo-gyroid geometries. The enhanced performance showed by the structured catalytic systems is mostly associated with the capability of the FGEs substrate geometries for efficient heat usages. Thus, variations on the channels diameter resulted in ca. 25% greater CO2 conversions values at intermediate temperature ranges. The highest void fraction evidenced in the best performing catalyst (3D-1) favored the radial heat transfer and resulted in significantly enhanced catalytic activity, achieving close to equilibrium (75%) conversions at 400 °C and 120 mL/min. For the 3D-1 catalyst, a mathematical model based on an experimental design was developed thus enabling the estimation of its behavior as a function of temperature, spatial velocity, hydrogen to carbon dioxide (H2/CO2) ratio, and inlet CO2 concentration. Its optimal operating conditions were established under 3 different scenarios: 1) no restrictions, 2) minimum H2:CO2 ratios, and 3) minimum temperatures and H2/CO2 ratio. For instance, for the lattest scenario, the best CO2 methanation conditions require operating at 431 °C, 200 mL/min, H2/CO2 = 3 M ratio, and inlet CO2 concentration = 10 %.
Ni/YMnO3 perovskite catalyst for CO2 methanation
(Elsevier, 2021-06) González Castaño, Míriam; Navarro de Miguel, Juan Carlos; Penkova, Anna Dimitrova; Centeno, M. A.; Odriozola Gordón, José Antonio; Arellano-García, H.; Química Inorgánica
This work proposes an innovative Ni catalyst supported over YMnO3 perovskite as a promising catalytic system for CO2 methanation reaction. Under reductive conditions, the attendance of Mn redox couples within the layered perovskite structure promotes the constitution of sub-stoichiometric YMnO3-x units which, by means of the flexible YMnO3-x reorganization capacity, results in boosted anionic mobility's. The competitive turnover frequencies (20.1 and 17.0 s−1 at 400 °C under dry- and steamed- CO2 methanation conditions) displayed by Ni/YMnO3 system were related to the synergism between strongly interacting Ni particles with partially reduced YMnO3-x perovskites. The optimal Ni dispersions, for which no relevant signs of sintering issues were discerned, combined to effective role of oxygen vacancies towards the dissociative activation of CO2 molecules enabled highly active and stable catalytic behaviours with no evidence of cooking phenomena. On evaluating the water presence within CO2 methanation feedstock's, the deprived catalytic behaviour was fundamentally associated to depleted oxygen vacancies concentrations and promoted WGS side reactions.
Cu supported Fe-SiO2 nanocomposites for reverse water gas shift reaction
(Elsevier, 2021-04) González Castaño, Míriam; Navarro de Miguel, Juan Carlos; Sinha, F.; Ghomsi Wabo, S.; Keplel, O.; Arellano García, H.; Química Inorgánica
This work analyses the catalytic activity displayed by Cu/SiO2, Cu-Fe/SiO2 and Cu/FSN (Fe-SiO2 nanocomposite) catalysts for the Reverse Water Gas Shift reaction. Compared to Cu/SiO2 catalyst, the presence of Fe resulted on higher CO’s selectivity and boosted resistances against the constitution of the deactivation carbonaceous species. Regarding the catalytic performance however, the extent of improvement attained through incorporation Fe species strongly relied on the catalysts’ configuration. At 30 L/gh and H2:CO2 ratios = 3, the performance of the catalysts’ series increased according to the sequence: Cu/SiO2 < Cu-Fe/SiO2 << Cu/FSN. The remarkable catalytic enhancements provided by Fe-SiO2 nanocomposites under different RWGS reaction atmospheres were associated to enhanced catalyst surface basicity’s and stronger Cu-support interactions. The catalytic promotion achieved by Fe-SiO2 nanocomposites argue an optimistic prospective for nanocomposite catalysts within future CO2-valorising technologies.
Monodentate, n-heterocyclic carbene-type coordination of 2,2'-bipyridine and 1,10-phenanthroline to iridium
(Wiley, 2008-05-16) Conejero, Salvador; Lara Muñoz, Patricia; Paneque, Margarita; Petronilho, Ana; Poveda, Manuel L.; Serrano, Oracio; Vattier Lagarrigue, María Florencia; Álvarez, Eleuterio; Maya Díaz, Celia María; Salazar, Verónica; Carmona Guzmán, Ernesto; Química Inorgánica
Mild Oxidation of C-C Bonds of Benzoiridacycles
(ACS, 2010-05-28) Padilla, Rosa; Salazar, Verónica; Paneque, Margarita; Alvarado-Rodríguez, José G.; Tamariz, Joaquín; Pacheco-Cuvas, Héctor; Vattier Lagarrigue, María Florencia; Química Inorgánica
We describe herein the formation of two metallacyclic derivatives, 4b and 5b, which contain a coordinated ketone functionality (from an α-keto ester metallacyclic substituent). An iridafuran, 6, that results from the reaction of TpMe2Ir(Ph)2(N2) (TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate) with di-tert-butyl acetylenedicarboxylate (DTAD) and oxygen is also reported. Our results reveal that the reactions proceed through iridacycle intermediates (detected by NMR) resulting formally from the coupling of one (in the case of 6) or two (for 4b and 5b) molecules of DTAD, with the metal unit “TpMe2Ir(C6H4)” derived from the iridium precursor. These intermediates experience very mild and selective oxidation by air to incorporate one (4b and 5b) or three (6) oxygen atoms in the final oxidation products.
Unveiling the potential of CaO-modified ZnO adsorbents for CO2 capture
(Elsevier, 2025-08-15) Goksu, Ali; Carrasco Ruiz, Sergio; Ramírez Reina, Tomás; Duyar, Melis Seher; Química Inorgánica; University of Surrey, United Kingdom; Engineering and Physical Sciences Research Council (EPSRC)
Intermediate-high temperature adsorbents are of interest as they can be used in process intensification and integrated CO2 capture and conversion processes to couple gas separation with a chemical reaction. Herein we develop CaO-modified ZnO as a new intermediate-high temperature CO2 adsorbent and show that the extent of CaO doping allows tuning of the CO2 adsorption/desorption temperature as well as capture capacity. Five different adsorbents were synthesized with Ca loadings of 0 %, 1 %, 5 %, 10 %, and 15 % by weight on ZnO and tested via fixed bed reactor experiments and TGA-DSC. The highest adsorption capacity was found to be 0.73 mmol/gcat for 5 %Ca/ZnO. The desorption temperatures for CO2 was found to also be influenced by Ca loading. Adsorbents were characterised by XRD, SEM, TGA, BET and ICP-MS, to understand their structure it was determined that CaO deposits on ZnO pores as separate domains. Herein we develop CaO-modified ZnO as a novel intermediate-high temperature CO₂ adsorbent, demonstrating tuneable adsorption/desorption characteristics through CaO dispersion on a ZnO scaffold.
Structure effect of modified biochar in Ru/C catalysts for sugar mixture hydrogenation
(Elsevier, 2022-08) Santos, J. L.; Sanz-Moral, L.M.; Aho, A.; Ivanova, Svetlana; Murzin, D. Yu; Centeno, M. A.; Química Inorgánica; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Consejería de Transformación Económica, Industria, Conocimiento y Universidades
This study deals with the production and activation of biochars and their use as supports for a series of ruthenium catalysts for hydrogenation of l-arabinose/d-galactose sugar mixture. The synthesized biochars differ in physicochemical properties and surface chemistry influencing ruthenium metal uptake and dispersion and as a consequence its catalytic behaviour. Selectivity exceeding 95% was observed for both hexitols. The catalytic performance of the prepared Ru supported catalysts is also compared to the already known Ru/activated carbon commercial catalyst.
TiO2-modified bentonite as a cost-effective support for nickel-based catalysts in dry reforming of methane
(Springer, 2025-07-30) Boudiaf, Meriem; Holgado, Juan P.; Halliche, Djamila; Caballero Martínez, Alfonso; Química Inorgánica; Junta de Andalucía; Ministerio de Ciencia e Innovación (MICIN). España
The potential of TiO2-modified bentonite as a cost-effective support for nickel-based catalysts in the dry reforming of methane (DRM) is highlighted. The comparison of a nickel catalyst supported on natural bentonite and one prepared on TiO2-modified bentonite revealed a significantly different behavior between the two catalysts under diluted and concentrated DRM reaction conditions. The unmodified bentonite catalyst, 15Ni/Na-Bent, exhibits high activity under diluted conditions (20CH4:20CO2:60He) but deactivates quickly under concentrated DRM conditions (40CH4:40CO2:20He). On the other hand, 15Ni/TiO2-Bent is less active at diluted conditions but demonstrates superior stability and activity in concentrated conditions. In situ XPS analysis of the O 1s, Al 2p, Si 2p, and Ti 2p regions of the calcined, reduced, and post-DRM samples revealed that TiO2 stabilizes the clay structure and prevents nickel reoxidation. The formation of TiO2-x species after reduction creates oxygen vacancies that trap oxidizing species in the reaction medium, thus limiting nickel reoxidation and reducing carbon deposition on the surface. Moreover, these TiO2-x species migrate to the nickel surface, forming a thin protective layer that partially encapsulates the nickel, improving metal–support interactions and providing resistance against sintering and reoxidation. In addition to XPS spectroscopy, which provided insights into the nature of the metal–support interactions in the 15Ni/Na-Bent and 15Ni/TiO2-Bent catalysts, the materials were also characterized using XRF, XRD, SEM, BET, TPR-H2, and Raman spectroscopy. These techniques offered complementary structural, textural, and morphological information, leading to a more comprehensive understanding of the catalysts’ physicoch emical properties.
Regioselective Syntheses of Bis(indazolyl)methane Isomers: Controlling Kinetics and Thermodynamics via Tunable Non-Innocent Amines
(American Chemical Society, 2025-11-13) Álvarez Sánchez, María; Gómez, Margarita; Santos Hurtado, Carina; Ngoune, Jean; Álvarez, Eleuterio; Galindo del Pozo, Agustín; Pettinari, Claudio; Química Inorgánica; Ministerio de Economía y Competitividad (MINECO). España; Ministerio de Ciencia, Innovación y Universidades (MICIU). España
The selective synthesis of regioisomers from ambident N-heterocycles remains a challenge in organic chemistry. We report a general and modular method for the regioselective syntheses of bis(indazolyl)methane isomers, in which the outcome is controlled by the nature of the base. Specifically, we employed structurally diverse amines as noninnocent bases, whose steric and electronic properties─particularly their pKaH and ability to act as methylene carriers or activators─play a decisive role in directing product distribution. By fine-tuning the amine structure, we achieved selective access to symmetrical and unsymmetrical isomers under mild, one-step conditions, without intermediate isolation. The use of amines over conventional inorganic bases was essential to enable both chemo- and regioselective control, while minimizing overactivation or competing pathways. Experimental findings were supported by DFT calculations that rationalize the observed selectivity through differential activation energies and intermediate stabilities. The methodology accommodates both classical methylenating agents (e.g., CH2Br2) and in situ generated ammonium-based donors. All compounds were fully characterized, and key products were confirmed by single-crystal X-ray diffraction (SCXRD). This strategy highlights the utility of noninnocent amines as tunable reagents for regioselective transformations of ambident nucleophiles, with broad potential applications in ligand design, supramolecular chemistry, and heterocyclic synthesis.
Refractive Index and Strain Modulation Tailor the Afterglow of Nanocomposite Films
(American Chemical Society, 2025-10-23) Castaing, Victor; Romero, Manuel; Drion, Théophile; Fernández Carrión, Alberto José; Lozano, Gabriel; Míguez, Hernán; Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España; European Union (UE); Ministerio de Ciencia, Innovación y Universidades (MICIU). España
Tailoring the unique delayed and long-lasting luminescence of persistent phosphors is crucial for their application in anticounterfeiting, data storage, imaging displays, and AC-driven lighting. We introduce a novel strategy to achieve this by modifying the refractive index of persistent phosphor transparent coatings. Specifically, we developed ZnGa2O4:Cr3+/SiO2 nanocomposite films with tunable refractive indices from 1.45 to 1.7. This tunability allowed us to precisely control the Cr3+ radiative decay rate, resulting in a substantial 1.7-fold increase in both luminescence and afterglow brightness. Furthermore, our approach uniquely influences the intrinsic charging rate of the phosphor, a mechanism attributed to the strain induced on the ZnGa2O4:Cr3+ nanocrystals by the presence of SiO2. This work demonstrates an unprecedent ability to manipulate the afterglow kinetics without altering the material composition, opening new avenues for designing and optimizing persistent luminescence materials
Insights into the physicochemical properties of Sugar Scum as a sustainable biosorbent derived from sugar refinery waste for efficient cationic dye removal
(Springer Nature, 2024) Atmani, F.; Kaci, M. M.; Yeddou-Mezenner, N.; Soukeur, A.; Akkari, I.; Navío Santos, José Antonio; Química Inorgánica
The objective of this study was to determine the ability of sugar scum (SS), an industrial waste, as a novel biosorbent for the removal of Basic Blue 41 (BB 41) from aqueous solutions. The biosorbent was characterized by SEM/EDS, BET, FTIR, and pHpzc measurements, respectively. To reach a maximum adsorption capacity of 26.45 mg.g–1, impacting operational factors such as pH, biosorbent dose, contact duration, starting dye concentration, and temperature were adjusted, when the removal efficiency reached 84% during 60 min at pH 10, 1.5 g.L–1 of biosorbent and Co = 10 mg.L–1. The experimental data were modeled by various isotherm models, whereas the best fit was found for Freundlich with a high correlation coefficient (R2 = 0.991). Other kinetic models including pseudo-first, pseudo-second order, and intra-particle diffusion models were tested to fit the kinetic data. The biosorption of BB 41 onto SS was spontaneous (∆G° < 0) and exothermic (∆H° < 0), while the biosoprtion mechanism of BB41 over SS was proposed with repeated reuse showing that SS could be regenerated after four successive runs. Furthermore, this study revealed that sugar scum is an underutilized bioresource in Algeria, with the potential to provide low-cost environmental removal of additional contaminants in the wastewater treatment domain.
Influence of vanadium species on the catalytic oxidation of glucose for formic acid production
(Elsevier, 2024-11-01) Álvarez-Hernández, Débora; Ivanova, Svetlana; Penkova, Anna Dimitrova; Centeno, Miguel Ángel; Química Inorgánica; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Agencia Estatal de Investigación. España
VOx/TiO2 catalysts with various theorical monolayer values have been prepared and used to study, for the first time, the effect of vanadium loading in the selective oxidation of glucose to formic acid. Monomeric or isolated vanadia species dominate at low loadings, evolving into polymeric chains at higher concentrations, while crystalline V2O5 is observed at loadings over the theoretical monolayer value. Their characterization by XRD, BET, ICP, DRIFTS, Raman, UV–vis, H2-TPR and NH3-TPD reveal distinct physicochemical characteristics influenced by the formed vanadia species, impacting sample acidity, reducibility, and catalytic activity. All catalysts exhibit significant activity, forming formic acid as the main product in the liquid phase and reaching a peak formic acid yield of 42 %. Post-reaction analysis reveals that the leaching-prone crystalline V2O5 compromises catalyst stability while isolated vanadia species demonstrate superior catalytic activity and leaching resistance. The findings of this study provide a strong basis for the development of a heterogeneous vanadia catalyst with improved interaction with the support.
Tautomerisation of 2-Substituted Pyridines to N-Heterocyclic Carbene Ligands Induced by the 16 e- Unsaturated [TpMe2IrIII(C6H5)2] Moiety
(Wiley, 2012-04-10) Conejero Iglesias, Salvador; López Serrano, Joaquín; Paneque Sosa, Margarita; Petronilho, Ana; Poveda, Manuel L.; Vattier Lagarrigue, María Florencia; Álvarez González, Eleuterio; Carmona Guzmán, Ernesto; Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía
The complex [Tp Me2Ir(C 6H 5) 2(N 2)] reacts with several 2-substituted pyridines to generate N-heterocyclic carbenes resulting from a formal 1,2-hydrogen shift from C 6 to N. In this paper we provide a detailed report of the scope and the mechanistic aspects (both experimental and theoretical) of the tautomerisation of 2-substituted pyridines.
Metallacyclic Pyridylidene Structures from Reactions of Terminal Pyridylidenes with Alkenes and Acetylene
(Wiley, 2010-04-28) Álvarez González, Eleuterio; Hernández, Yohar A.; López Serrano, Joaquín; Maya Díaz, Celia María; Paneque Sosa, Margarita; Petronilho, Ana; Poveda, Manuel L.; Salazar, Verónica; Vattier Lagarrigue, María Florencia; Carmona Guzmán, Ernesto; Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía; Portuguese FCT; Consejo Nacional de Ciencia y Tecnología (CONACYT). México
(Chemical Equotion Present). Iridium pyridyl species are key intermediates in the title reactions. Thermal elimination of benzene from complexes 1 (R = Me, Ph) creates a vacant coordination site accessible to unsaturated hydrocarbons. Subsequent intramolecular nucleophilic attack by the pyridyl nitrogen atom to the alkene or vinylidene leads to iridacyclic pyridylidene structures (see scheme).
Dicoordinate Au(I)−Ethylene Complexes as Hydroamination Catalysts
(American Chemical Society, 2022-03-23) Navarro, Miquel; González Alférez, Macarena; Sousa, Morgane de; Miranda Pizarro, Juan; Campos, Jesús; Química Inorgánica; European Research Council (ERC); Ministerio de Ciencia e Innovación (MICIN). España
A series of gold(I)–ethylene π-complexes containing a family of bulky phosphine ligands has been prepared. The use of these sterically congested ligands is crucial to stabilize the gold(I)–ethylene bond and prevent decomposition, boosting up their catalytic performance in the highly underexplored hydroamination of ethylene. The precatalysts bearing the most sterically demanding phosphines showed the best results reaching full conversion to the hydroaminated products under notably mild conditions (1 bar of ethylene pressure at 60 °C). Kinetic analysis together with density functional theory calculations revealed that the assistance of a second molecule of the nucleophile as a proton shuttle is preferred even when using an extremely congested cavity-shaped Au(I) complex. In addition, we have measured a strong primary kinetic isotopic effect that is consistent with the involvement of X–H bond-breaking events in the protodeauration turnover-limiting step.
Multiple C-B Bond Cleavage Reactions at [BArF 4]- Anions Mediated by Terphenyl Phosphine Gold Catalysts
(American Chemical Society, 2025-01-13) Miranda Pizarro, Juan; Navarro, Miquel; Campos, Jesús; Química Inorgánica; Ministerio de Ciencia e Innovación (MICIN). España; Junta de Andalucía
Fluorinated borates have been widely used as innocent and weakly coordinating counteranions. Among those, [BArF4]− ([B(C6H3-3,5-(CF3)2)4]−) occupies a prominent position due to the robustness of its B–C carbon bonds. Herein, we investigate C–B bond cleavage in the [BArF4]− anion mediated by cationic gold fragments of type [Au(PMe2Ar′)]+, where Ar′ stands for bulky terphenyl (C6H3-2,6-Ar2) substituents. In addition, we have exploited the stoichiometric B–C bond cleavage to construct a catalytic cycle for the synthesis of boranes under acidic conditions.
Catalyzed hydrothermal carbonization of sewage sludge: structural modification of hydrochar and its derived selective pyrolytic product distribution
(Royal Society Chemistry, 2025) Rizwan, Muhammad; Zhou, Xiaolong; Leghari, Asma; Sarfraz Akram, Muhammad; Zeb, Hassan; Frayad Ali, Muhammad; Kashif Javed, Muhammad; Wang, Mingzhi; Nawaz, Muhammad Asif; Química Inorgánica
The pressing demand for sustainable alternatives to fossil fuels coupled with environmental risks associated with inappropriate sewage sludge (SS) disposal calls for innovative valorization strategies that transform waste into value-added products. This study introduces a novel approach by directly incorporating zeolite catalysts (HZSM-5 and USY) into the hydrothermal carbonization (HTC) of SS, followed by pyrolysis (Py) of the derived hydrochar (HC). Insights into derived HC are explored through comprehensive characterization, such as morphology, crystallinity, functionality, and thermal analysis. HZSM-5 significantly reduced the activation energy of HC from 27 to 5.5 kJ mol−1, while increasing the structural disorder (ID/IG0.73). The selective production of CO and H2 was achieved through temperature-dependent pyrolysis between 500 and 900 °C. HZSM-5 facilitated an increase in CO production to 54.18%, whereas USY boosted CO yield up to 35.6%. The optimal product distribution was achieved by strategically incorporating zeolite catalysts, allowing for precise control of N and O functionality and promoting selective syngas and chemical precursors yield. This innovative catalyst-mediated HTC-Py cascade offers unique control over pyrolytic products by introducing an efficient pathway for transforming problematic SS into green energy carriers, thus bridging the gap between environmental sustainability and feasible industrial utilization.
Catalytic activation of nitrous oxide: boryl versus hydride nickel complexes
(Royal Society Chemistry, 2025) Laglera Gándara, Carlos J.; Mora-Fernández, Elena; Peloso, Riccardo; Ríos Moreno, Pablo; Rodríguez, Amor; Química Inorgánica; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; Agencia Estatal de Investigación. España; Universidad de Oviedo
The selective reduction of nitrous oxide (N2O), a potent greenhouse gas with harmful effects on the ozone layer, remains a significant challenge in small-molecule activation. Herein, we report the efficient deoxygenation of N2O using bis(phosphino)boryl-nickel hydride (3) and bis-boryl nickel complexes (4 and 5) under mild conditions (1–2 bar N2O, 2–5 mol% catalyst loading, and 25 °C). Both catalytic systems exhibit high activity in the presence of boranes and diboranes, achieving complete N2O conversion within 30 minutes using catecholborane as the reductant. Mechanistic investigations, including stoichiometric experiments, kinetic studies, and density functional theory (DFT) calculations support the formation of nickel boroxide intermediates, (RPBP)Ni–OBR2, as key species within the catalytic cycle, while pathways involving nickel hydroxide species, (RPBP)Ni–OH, are disfavored. These results provide valuable mechanistic insights into key aspects of N2O reduction chemistry thereby enabling the rational design of transition-metal catalysts for the activation of small-molecules.
Non-bifunctional Mn catalysts based on phosphine-phosphites for the hydrogenation of carbonyl substrates
(Royal Society of Chemistry, 2025-09-22) Jiménez, Verónica; González, Carmen; López Serrano, Joaquín; Fernández de Córdova, Francisco; Pizzano, Antonio; Química Inorgánica; Ministerio de Ciencia, Innovación y Universidades (MICIU). España; European Union (UE)
A series of Mn(I) complexes bearing phosphine–phosphite ligands (P-OP) of formula [Mn(Br)(P-OP)(CO)3] (1) have been prepared and characterised. These compounds exist in solution as a mixture of fac and mer isomers with fac/mer ratios from 18 : 1 to 2 : 1. The relatively low donor ability of P-OP compared to bis(trialkylphosphines) or bis–NHC ligands, typically found in non-bifunctional Mn catalysts reported to date, is evinced in IR spectra. Compounds 1 provide efficient catalysts for the hydrogenation of carbonyl substrates using KOtBu as a base. Notably, these complexes constitute a set of modularly designed precatalysts and optimisation of the P-OP ligand provided appropriate catalysts for the reduction of a wide variety of aldehydes and ketones under mild reaction conditions (S/C = 250–500, 20 bar H2, RT to 40 °C). A mechanistic study combining spectroscopic and computational results provides support for a catalyst activation process based on the nucleophilic attack of the alkoxide on a coordinated CO in [Mn(OtBu)(P-OP)(CO)3], as well as a non-bifunctional inner-sphere hydrogenation pathway in the representative hydrogenation of benzophenone. The catalytic cycle is also characterised by a rather stable pentacoordinated alkoxide [Mn(k1-O–OCHPh2)(P-OP)(CO)2] which determines the energetic span of the reaction.

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