Yulia H. Budnikova

Highly reactive σ-organonickel complexes in electrocatalytic processes

Abstract The electrochemical reduction of nickel complexes with 2,2′-bipyridine in the presence of ortho -substituted organic halides or white phosphorus yields the highly reactive σ-organonickel complexes. These complexes selectively react with organic halides forming cross-coupling products. The mechanism of these processes was investigated using the method of cyclic voltammetry and preparative electrolysis. The key intermediates of electrochemical functioning of white phosphorus in conditions of metallocomplex catalysis were detected.

New Functional Cyclic Aminomethylphosphine Ligands for the Construction of Catalysts for Electrochemical Hydrogen Transformations

Eight-membered cyclic functional bisphosphines, namely 1,5-di-aryl-3,7-di(2-pyridyl)-1,5-diaza-3,7-diphosphacyclooctanes (aryl=2-pyridyl, m-tolyl, p-tolyl, diphenylmethyl, benzyl, (R)-(+)-(α-methyl)benzyl), with 2-pyridyl substituents on the phosphorus atoms have been synthesized by condensation of 2-pyridylphosphine, formaldehyde, and the corresponding primary amine. The structures of some of these bisphosphines have been investigated by X-ray crystallography. The bisphosphines readily form neutral P,P-chelate complexes [(κ(2)-P,P-L)MCl2], cationic bis-P,P-chelate complexes [(κ(2)-P,P-L)2 M](2+), or a five-coordinate complex [(κ(2)-P,P-L)2 NiBr]Br. The electrochemical behavior of two of the nickel complexes, and their catalytic activities in electrochemical hydrogen evolution and hydrogen oxidation, including the fuel-cell test, have been studied.

Electrochemical properties of diphosphonate-bridged palladacycles and their reactivity in arene phosphonation

A series of diphosphonate-bridged dipalladacycles [(phpy)Pd(EtO)2P(O)]2, [(bhq)Pd(EtO)2P(O)]2, [(phpz)Pd(EtO)2P(O)]2 (phpy=2-phenylpyridine, bhq=benzo[h]quinoline, phpz=1-phenylpyrazole), which are known to be involved in catalytic C–H phosphonation reactions, was prepared and characterized by NMR spectroscopy and cyclic voltammetry in acetonitrile solutions and in carbon paste electrode. Diphosphonate dipalladacycles are oxidized irreversibly at more positive potentials as distinguished from related acetate palladacycles. Electrochemical preparative oxidations carried out under mild conditions without any specially added oxidants quantitatively afforded corresponding arylphosphonates. For complete conversion of dipalladacycles into arylphosphonates, four electrons per each palladium atom are required, that probably indicates a mechanism involving Pd(IV)/Pd(II) redox couple.

One-stage synthesis of FcP(O)(OC2H5)2 from ferrocene and α-hydroxyethylphosphonate

A new approach is proposed for ferrocene phosphorylation using α-hydroxylalkylphosphonate as a “masked” phosphorylating agent, by electrochemical reduction of a ferrocene and (Me)2C(OH)P(O)(OC2H5)2 mixture at −50 °C. The method makes it possible to obtain the product of diethyl ferrocenyl phosphonate with a high yield (87–89%) and 100% conversion of the initial phosphonate in one stage. It is evidenced with experiments that ferrocene reduction is carried out with preservation of the iron charge in the ferrocene fragment and with the formation of a cyclopentadienyl ligand radical anion at −3.3 V ref. Ag/AgCl (at −50 °C).

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.

Nickel Complexes Based on Thiophosphorylated Calix[4]Resorcinols as Effective Catalysts for Hydrogen Evolution

Nickel complexes of thiophosphorylated calix[4]resorcinols showed high catalytic activity for hydrogen evolution from acidic solutions and stability in the electro-assisted catalysis at the surface of both glassy carbon and Hg-pool electrodes. The conformation of the macrocyclic ligand determines the dimensionality and shape of the catalytically active species generated on the electrode.

Electrochemical oxidative phosphonation of azoles

GRAPHICAL ABSTRACT ABSTRACT Metal-catalyzed electrochemical oxidative phosphonation of hetaryl-azoles (benzoxazoles, benzothiazole and others) with dialkyl-H-phosphonate was developed. Joint electrochemical oxidation of azoles and dialkyl-H-phosphonate mixtures in the presence of catalytic quantities of salts of transition metals at room temperature affords the desired 2-substituted azoles. Palladium, nickel and silver salts were tested as catalysts.

The role of Ni(0) complexes in electrochemical phosphorylation of organic halides part 1. Factors determining catalytic activity

Abstract The catalytic efficiency of Ni(0) complexes in coupling reactions of organic and organoelemental halides is shown to be determined by the degree of charge transfer, the value of the electrochemical gap, and the availability or absence of competitive redox reactions.

Eco-efficient electrocatalytic C–P bond formation

Abstract The development of practical, efficient and atom-economical methods of formation of carbon-phosphorus bonds remains a topic of considerable interest for the current synthetic organic chemistry and electrochemistry. This review summarizes selected topics from the recent publications with particular emphasis on phosphine and phosphine oxides formation from white phosphorus, chlorophosphines in electrocatalytic processes using aryl, hetaryl or perfluoroalkyl halides as reagents. This review includes selected highlights concerning recent progress in modification of catalytic systems for aromatic C–H bonds phosphonation involving metal-catalyzed ligand directed or metal-induced oxidative processes. Furthermore, a part of this review is devoted to phosphorylation of olefins with white phosphorus under reductive conditions in water-organic media. Finally, we have also documented recent advances in ferrocene C–H activation and phosphorylation.

Electrochemical pathway to CH/PH functionalization of diphenylphosphine oxide

GRAPHICAL ABSTRACT ABSTRACT Electrochemical oxidative CH/PH functionalization reaction between diphenylphosphine oxide and diphenylacetylene has been performed. The yield of target cyclisation product was obtained with 76% yield after 4F of electricity was passed through the reaction mixture at 1.0 V (vs. Ag/AgCl).