A. V. Rokhin

Hydrogenation catalysts based on polynuclear palladium complexes with organophosphorus ligands

A new procedure is proposed for the preparation of hydrogenation catalysts. This procedure includes the synthesis of cyclic tetranuclear palladium complexes with bridging diphenylphosphide ligands followed by a reaction with Pd(CH3COO)2 in the presence of hydrogen to form nanosized particles. In the test catalysts, the ensembles of palladium atoms (or palladium hydrides) immobilized on supramolecular structures formed by the association of phosphinidene and phosphide complexes of palladium are responsible for the catalytic activity.

Formation, nature of activity, and hydrogenation catalysis by nickel bis(acetylacetonate)-lithium tetrahydroaluminate systems

A new approach to synthesis of nickel catalysts under the action of lithium tetrahydroaluminate was proposed which allows preparation of high-performance nanosized catalytic systems with well-reproducible properties. The major stages of formation and the nature of catalytically active species and inhibitors formed in the Ni(acac)2-LiAlH4 system were determined. The catalytic properties of the nickel nanoclusters were studied in relation to the nature and concentration of the proton-containing compounds. Factors responsible for the promoting action exhibited by these compounds were analyzed.

Nanosized hydrogenation catalyst based on palladium bisacetylacetonate and phosphine: Formation, the origin of activity, and properties

The nature and catalytic properties of a hydrogenation catalyst based on Pd(acac)2 and PH3 are considered. As demonstrated by a variety of physicochemical methods (IR and UV spectroscopy, 31P and 1H NMR, electron microscopy, and X-ray powder diffraction), nanoparticles consisting of various palladium phosphides (Pd6P, Pd4.8P, and Pd5P2) and Pd(0) clusters form under the action of dihydrogen during catalyst preparation. The promoting effect of phosphine at low PH3: Pd(acac)2 ratios is mainly due to the ability of phosphine to increase the extent of dispersion of the catalyst.

Catalysis of dimerization and oligomerization reactions of lower alkenes by systems based on Ni(PPh3)2(C2H4) and Ni(PPh3)nCl (n = 2 or 3)

The catalytic characteristics of the individual complex Ni(PPh3)2(C2H4) and Ni(PPh3)nCl (n = 2 or 3) and those of systems based on these complexes in combination with Brönsted and Lewis acids in ethylene and propylene oligomerization have been determined. A correlation between the BF3 · OEt2 solution storage time and the catalytic properties of the nickel systems has been established for the reactions of the lower alkenes. The observed increase in the turnover frequency and turnover number of the catalyst is due to the increase in the Brörsted acid concentration as a result of irreversible conversions of BF3 · OEt2 caused by its interaction with impurity water in the solvent. The formation of the Ni(PPh3)2(C2H4)-BF3 · OEt2 catalytic system in the presence of a substrate dramatically extends the system’s service life. The interaction of the nickel precursors with boron trifluoride etherate has been investigated using a complex of physical methods, and the main reactions yielding catalytically active species have been revealed.

Formation and properties of nickel catalysts for hydrogenation under the action of lithium Di- and tris(tert-butoxy)hydroaluminates

It was demonstrated that systems based on Ni(II) compounds and the alkoxyhydride derivatives LiAlH(tert-BuO)3 and LiAlH2(tert-BuO)2, in contrast to LiAlH4, exhibit high catalytic activity in the reaction of styrene hydrogenation in the absence of activators. The inhibiting effect of an excess of LiAlH2(tert-BuO)2 was found. The analysis of the composition of reaction mixtures by NMR, EPR, and UV spectroscopy and TEM showed that side reactions of the conversion of aluminum-containing components occurred together with the formation of nickel nanoclusters. The most probable reaction schemes of LiAlH(tert-BuO)3 and LiAlH2(tert-BuO)2 disproportionation were proposed. The nature of the stabilizers of nickel nanoparticles was considered.

Hydrogenation catalysts based on palladium bisacetylacetonate and lithium tetrahydroaluminate: Formation mechanism and reasons for modified effect of water

Mechanism of formation, nature of activity, and properties of species active in hydrogenation catalysis in systems based on Pd(acac)2 and LiAlH4 were studied. The effect consisting in activation of catalytic systems was observed and reasons for the modifying action of water were considered.

Reaction of Palladium Bis(acetylacetonate) with Diphenylphosphine: Spectral Studies

Interaction of palladium bis(acetylacetonate) with diphenylphosphine is studied by NMR, IR, and UV methods. Reaction between reagents taken in equimolar amounts gives binuclear and trinuclear palladium complexes with bridging diphenylphosphide and the chelate acetylacetonate [Pd(Acac)PPh2]2 and [Pd3(Acac)2(PPh2)4] ligands. With excess PPh2H, the trinuclear palladium complex, whose composition is supposed to be [Pd3(PPh2)4(PPh2–PPh2) · C6H6], is isolated and characterized on the basis of the spectral data.

Bioconversion of D-glucose in heavy water: Effect of water isotopomeric composition on deuterium fragment distribution in ethanol

The relative distribution of deuterium between methyl and methylene groups in ethanol at the bioconversion of D-glucose in heavy water was studied.

On the synthesis and structure of resol phenol-formaldehyde resins

Chemical structure of the SFZh-3013 standard resol phenol-formaldehyde resin was studied by the method of quantitative 13C NMR spectroscopy.

Coupled hydrogenation of alkenes and arenes in the presence of catalytic systems based on cobalt Bis(acetylacetonate) and tributylphosphine

The effect of the composition of the catalytic systems based on Co(acac)2 and tertiary phosphines on the activity and efficiency of cobalt catalysts in the coupled hydrogenation of alkenes and arenes is reported. The process occurs in the presence of cobalt catalysts formed under the action of both organoaluminum compounds and tert-butoxy derivatives of complex aluminum hydrides. NMR and IR spectroscopic methods show that the interaction of the components of the catalytic systems yields mono- and/or trihydrido cobalt phosphine complexes, whose composition depends on the nature of the reducing agent and gas atmosphere. The homogeneous character of the process is hypothesized. The most probable schemes are proposed for the reaction mechanism, according to which the kinetic coupling of alkene (alkadiene) and arene hydrogenations is due to the fact that the reaction proceeds through a σ-alkyl or σ-alkenyl cobalt complex with two phosphorus-containing ligands.