Non-Noble-Metal Mono and Bimetallic Composites for Efficient Electrocatalysis of Phosphine Oxide and Acetylene C-H/P-H Coupling under Mild Conditions.

The present work describes an efficient reaction of electrochemical phosphorylation of phenylacetylene controlled by the composition of catalytic nanoparticles based on non-noble-metals. The sought-after products are produced via the simple synthetic protocol based on room temperature, atom-economical reactions, and silica nanoparticles (SNs) loaded by one or two d-metal ions as nanocatalysts. The redox and catalytic properties of SNs can be tuned with a range of parameters, such as compositions of the bimetallic systems, their preparation method, and morphology. Monometallic SNs give phosphorylated acetylene with retention of the triple bond, and bimetallic SNs give a bis-phosphorylation product. This is the first example of acetylene and phosphine oxide C-H/P-H coupling with a regenerable and recyclable catalyst.

Recent advances in electrochemical C-H phosphorylation.

The activation of C-H bond, and its direct one-step functionalization, is one of the key synthetic methodologies that provides direct access to a variety of practically significant compounds. Particular attention is focused on modifications obtained at the final stages of the synthesis of complicated molecules, which requires high tolerance to the presence of existing functional groups. Phosphorus is an indispensable element of life, and phosphorus chemistry is now experiencing a renaissance due to new emerging applications in medicinal chemistry, materials chemistry (polymers, flame retardants, organic electronics, and photonics), agricultural chemistry (herbicides, insecticides), catalysis (ligands) and other important areas of science and technology. In this regard, the search for new, more selective, low-waste synthetic routes become relevant. In this context, electrosynthesis has proven to be an eco-efficient and convenient approach in many respects, where the reagents are replaced by electrodes, where the reactants are replaced by electrodes, and the applied potential the applied potential determines their "oxidizing or reducing ability". An electrochemical approach to such processes is being developed rapidly and demonstrates some advantages over traditional classical methods of C-H phosphorylation. The main reasons for success are the exclusion of excess reagents from the reaction system: such as oxidants, reducing agents, and sometimes metal and/or other improvers, which challenge isolation, increase the wastes and reduce the yield due to frequent incompatibility with these functional groups. Ideal conditions include electron as a reactant (regulated by applied potential) and the by-products as hydrogen or hydrocarbon. The review summarizes and analyzes the achievements of electrochemical methods for the preparation of various phosphorus derivatives with carbon-phosphorus bonds, and collects data on the redox properties of the most commonly used phosphorus precursors. Electrochemically induced reactions both with and without catalyst metals, where competitive oxidation of precursors leads to either the activation of C-H bond or to the generation of phosphorus-centered radicals (radical cations) or metal high oxidation states will be examined. The review focuses on publications from the past 5 years.

Nano-architecture of silica nanoparticles as a tool to tune both electrochemical and catalytic behavior of NiII@SiO2.

The present work introduces a facile synthetic route for efficient doping of [NiII(bpy) x ] into silica nanoparticles with various sizes and architectures. Variation of the latter results in different concentrations of the NiII complexes at the interface of the composite nanoparticles. The UV-Vis analysis of the nanoparticles reveals changes in the inner-sphere environment of the NiII complexes when embedded into the nanoparticles, while the inner-sphere of NiII is invariant for the nanoparticles with different architecture. Comparative analysis of the electrochemically generated redox transformations of the NiII complexes embedded in the nanoparticles of various architectures reveals the latter as the main factor controlling the accessibility of NiII complexes to the redox transitions which, in turn, controls the electrochemical behavior of the nanoparticles. The work also highlights an impact of the nanoparticulate architecture in catalytic activity of the NiII complexes within the different nanoparticles in oxidative C-H fluoroalkylation of caffeine. Both low leakage and high concentration of the NiII complexes at the interface of the composite nanoparticles enables fluoroalkylated caffeine to be obtained in high yields under recycling of the nanocatalyst five times at least.

A Ni(iii) complex stabilized by silica nanoparticles as an efficient nanoheterogeneous catalyst for oxidative C-H fluoroalkylation.

We have developed Ni(III)-doped silica nanoparticles ([(bpy)xNi(III)]@SiO2) as a recyclable, low-leaching, and efficient oxidative functionalization nanocatalyst for aromatic C-H bonds. The catalyst is obtained by doping the complex [(bpy)3Ni(II)] on silica nanoparticles along with its subsequent electrooxidation to [(bpy)xNi(III)] without an additional oxidant. The coupling reaction of arenes with perfluoroheptanoic acid occurs with 100% conversion of reactants in a single step at room temperature under nanoheterogeneous conditions. The catalyst content is only 1% with respect to the substrates under electrochemical regeneration conditions. The catalyst can be easily separated from the reaction mixture and reused a minimum of five times. The results emphasize immobilization on the silica support and the electrochemical regeneration of Ni(III) complexes as a facile route for developing an efficient nanocatalyst for oxidative functionalization.

Redox trends in cyclometalated palladium(ii) complexes.

A series of diverse binuclear and mononuclear cyclometalated palladium(ii) complexes of different structure was investigated by electrochemical techniques combined with density functional theory (DFT) calculations. The studies including cyclic and differential pulse voltammetry, X-ray structure analysis and quantum chemical calculations revealed a regularity of the complexes oxidation potential on the metal-metal distance in the complexes: the larger Pd-Pd distance, the higher oxidation potentials. The reduction potentials feature unusually high negative values while no correlation depending on the structure could be observed. These results are in a good agreement with the electron density distribution in the complexes. Additionally, ESR data obtained for the complexes upon oxidation is reported.

Nanoheterogeneous catalysis in electrochemically induced olefin perfluoroalkylation.

Ni-catalyzed electroreductive olefin perfluoroalkylation affords both monomeric and dimeric products depending on the reaction media. Recycling of the catalyst can be achieved by immobilization of a (bpy)NiBr2 complex on silica nanoparticles decorated with anchoring amino-groups. Switching the homogeneous and heterogeneous catalysts is found to be one more factor to control the product ratio. This catalytic technique is both green and atom economical and combines the advantages of nanoheterogeneous catalysis and electrocatalysis.