scholarly journals Evaluation of Transition Metal Catalysts in Electrochemically Induced Aromatic Phosphonation

Molecules ◽  
2019 ◽  
Vol 24 (9) ◽  
pp. 1823
Author(s):  
Sofia Strekalova ◽  
Mikhail Khrizanforov ◽  
Yulia Budnikova
Keyword(s):  
Transition Metal ◽  
Metal Ion ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Catalytic Systems ◽  
Catalytic Current ◽  
Metal Phosphonates ◽  
Quantitative Characteristics ◽  
Phosphorus Precursor ◽  
Phosphonyl Radical

Voltammetry provides important information on the redox properties of catalysts (transition metal complexes of Ni, Co, Mn, etc.) and their activity in electrocatalytic reactions of aromatic C–H phosphonation in the presence of a phosphorus precursor, for example, dialkyl-H-phosphonate. Based on catalytic current growth of oxidation or reduction of the metal catalysts (CoII, MnII, NiII, MnII/NiII, MnII/CoII, and CoII/NiII), quantitative characteristics of the regeneration of catalysts were determined, for example, for MnII, NiII and MnII/NiII, CoII/NiII pairs. Calculations confirmed the previously made synthetic observations on the synergistic effect of certain metal ions in binary catalytic systems (MnIIbpy/NiIIbpy and NiIIbpy/CoIIbpy); for mixtures, the observed rate constants, or TOF, were 690 s−1 and 721 s−1, respectively, and product yields were higher for monometallic catalytic systems (up to 71% for bimetallic catalytic systems and ~30% for monometallic catalytic systems). In some cases, the appearance of pre-waves after adding H-phosphonates confirmed the preceding chemical reaction. It also confirmed the formation of metal phosphonates in the time scale of voltammetry, oxidizing or reducing at lower potentials than the original (RO)2P(O)H and metal complex, which could be used for fast diagnostics of metal ion and dialkyl-H-phosphonate interactions. Electrochemical transfer of an electron to (from) metal phosphonate generates a phosphonyl radical, which can then react with different arenes to give the products of aromatic C–H phosphonation.

Sulfur-Mediated Reactions through Sulfonium Salts and Ylides

Synlett ◽  
2021 ◽  
Author(s):  
Pingfan Li
Keyword(s):  
Transition Metal ◽  
Rational Design ◽  
Acid Catalysis ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Bronsted Acid ◽  
Proof Of Concept ◽  
Sulfonium Salts ◽  
Brönsted Acid ◽  
Sulfonium Ylides

AbstractThis Account discusses several new reaction methods developed in our group that utilize sulfur-mediated reactions through sulfonium salts and ylides, highlighting the interplay of rational design and serendipity. Our initial goal was to convert aliphatic C–H bonds into C–C bonds site-selectively, and without the use of transition-metal catalysts. While a proof-of-concept has been achieved, this target is far from being ideally realized. The unexpected discovery of an anti-Markovnikov rearrangement and subsequent studies on difunctionalization of alkynes were much more straightforward, and eventually led to the new possibility of asymmetric N–H insertion of sulfonium ylides through Brønsted acid catalysis.1 Introduction2 Allylic/Propargylic C–H Functionalization3 Anti-Markovnikov Rearrangement4 Difunctionalization of Alkynes5 Asymmetric N–H Insertion of Sulfonium Ylides6 Conclusion

scholarly journals Facet-Dependent Reactivity of Ceria Nanoparticles Exemplified by CeO2-Based Transition Metal Catalysts: A Critical Review

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 452
Author(s):  
Michalis Konsolakis ◽  
Maria Lykaki
Keyword(s):  
Transition Metal ◽  
Co Oxidation ◽  
Critical Review ◽  
Rational Design ◽  
Metal Catalysts ◽  
Co2 Hydrogenation ◽  
Transition Metal Catalysts ◽  
Fine Tuning ◽  
Ceria Nanoparticles ◽  
Highly Active

The rational design and fabrication of highly-active and cost-efficient catalytic materials constitutes the main research pillar in catalysis field. In this context, the fine-tuning of size and shape at the nanometer scale can exert an intense impact not only on the inherent reactivity of catalyst’s counterparts but also on their interfacial interactions; it can also opening up new horizons for the development of highly active and robust materials. The present critical review, focusing mainly on our recent advances on the topic, aims to highlight the pivotal role of shape engineering in catalysis, exemplified by noble metal-free, CeO2-based transition metal catalysts (TMs/CeO2). The underlying mechanism of facet-dependent reactivity is initially discussed. The main implications of ceria nanoparticles’ shape engineering (rods, cubes, and polyhedra) in catalysis are next discussed, on the ground of some of the most pertinent heterogeneous reactions, such as CO2 hydrogenation, CO oxidation, and N2O decomposition. It is clearly revealed that shape functionalization can remarkably affect the intrinsic features and in turn the reactivity of ceria nanoparticles. More importantly, by combining ceria nanoparticles (CeO2 NPs) of specific architecture with various transition metals (e.g., Cu, Fe, Co, and Ni) remarkably active multifunctional composites can be obtained due mainly to the synergistic metalceria interactions. From the practical point of view, novel catalyst formulations with similar or even superior reactivity to that of noble metals can be obtained by co-adjusting the shape and composition of mixed oxides, such as Cu/ceria nanorods for CO oxidation and Ni/ceria nanorods for CO2 hydrogenation. The conclusions derived could provide the design principles of earth-abundant metal oxide catalysts for various real-life environmental and energy applications.

scholarly journals The Effect of Iron Impurities on Transition Metal Catalysts for the Oxygen Evolution Reaction in Alkaline Environment: Activity Mediators or Active Sites?

2020 ◽  
Author(s):  
Ioannis Spanos ◽  
Justus Masa ◽  
Aleksandar Zeradjanin ◽  
Robert Schlögl
Keyword(s):  
Transition Metal ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
Active Sites ◽  
Water Electrolysis ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Alkaline Water Electrolysis ◽  
Co Catalysts ◽  
Model Transition

AbstractThere is an ongoing debate on elucidating the actual role of Fe impurities in alkaline water electrolysis, acting either as reactivity mediators or as co-catalysts through synergistic interaction with the main catalyst material. This perspective summarizes the most prominent oxygen evolution reaction (OER) mechanisms mostly for Ni-based oxides as model transition metal catalysts and highlights the effect of Fe incorporation on the catalyst surface in the form of impurities originating from the electrolyte or co-precipitated in the catalyst lattice, in modulating the OER reaction kinetics, mechanism and stability. Graphic Abstract

scholarly journals Early-stage formation of (hydr)oxo bridges in transition-metal catalysts for photosynthetic processes

2021 ◽  
Author(s):  
Shin Nakamura ◽  
Matteo Capone ◽  
Giuseppe Mattioli ◽  
Leonardo Guidoni
Keyword(s):  
Transition Metal ◽  
Aqueous Solutions ◽  
Ab Initio ◽  
Early Stage ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Electrochemical Potential ◽  
Ab Initio Simulations

Water-oxidizing metal-(hydr)oxo catalyst films can be generally deposited and activated by applying a positive electrochemical potential to suitable starting aqueous solutions. Here, we used ab initio simulations based on density...

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