Heterogeneous catalytic condensation of propanal

Russian Chemical Bulletin - The aldol homocondensation of propanal was studied in the presence of a heterogeneous titanium oxide catalyst modified with amino acid (AA) l-norleucine. The effects of...     

The formation of palladium nanocomposite catalysts on the porous silicon used as anodes of fuel cells

Palladium nanoparticles on the porous silicon were synthesized by radiation-chemical reduction in the solution of reversed micelles. The Pd nanoparticles obtained are electron deficient. The porosity, the type of conductivity, the silicon matrix pore geometry, and precursor parameters influence the size, the shape and the charge state of palladium catalysts. The mechanism of H₂ and HCOOH electrooxidation on porous silica in the presence of Pd+/Pd redox pair is proposed.     

Reactivity of palladium(II) complexes supported on carbon toward molecular hydrogen

The reactivity of Pd(II) complexes supported on carbon toward H₂ was studied. For the carboxylate complexes Pd(RCOO)₂ (R = Me, Me₃C, F₃C), it decreases upon decrease in the basicity of the acid RCO₂H. The reactivity of Pd(II) η³-allyl complexes increases with increase in the Mulliken charges on the C atom of the allyl ligand connected to the substituent R. The results are in line with the heterocyclic mechanism of H-H bond activation in the hydrogen molecule and can be used for optimization of the composition of the initial compounds for the preparation of palladium catalysts.     

New catalyst for homocoupling of aryl halides based on nickel complexes with diazabutadiene ligands

Russian Journal of Organic Chemistry -     

New Approaches to the Synthesis of 2,2′: 6′,2″-Terpyridine and Some of Its Derivatives

A new two-step procedure has been developed for the synthesis of 2,2′: 6′,2″-terpyridine and 4′-methylsulfanyl-2,2′: 6′,2″-terpyridine in more than 70% yield on the basis of Potts’ condensation. Efficient methods have been proposed for purification of all condensation products.     

Theoretical modeling of the mechanism of aniline oxidation by singlet O<Subscript>2</Subscript>

The mechanism of aniline oxidation by singlet oxygen was studied by the DFT-PBE/L2 method. According to the calculations, aniline endoperoxide cannot participate in the reaction because of its energy instability. The addition of ¹O₂ to aniline proceeds with the simultaneous proton transfer to the oxygen molecule from the NH₂ group (for the syn-approach of oxygen) or from the aromatic ring (for the anti-approach). For the syn-approach of the ¹O₂ molecule, the HNC₆H₄(H)OOH intermediate is formed, whose decomposition leads to aniline p-hydroperoxide (predominantly) or p-iminoquinone. In the case of the anti-approach, the ¹O₂ molecule is inserted at the C–H bond to form aniline p-hydroperoxide (H₂NC₆H₄OOH). The decomposition of aniline p-hydroperoxide with the formation of p-aminophenol and H₂O₂ molecule proceeds via concerted mechanism.     

Synthesis and properties of alternating copolymers of carbon monoxide with 5-vinyl-2-norbornene

The alternating cooligomers of carbon monoxide and 5-vinyl-2-norbornene have been first synthesized in the presence of catalysts based on palladium complexes containing N^N and P^P ligands. It has been shown that the insertion of carbon monoxide proceeds for the most part via a C(2)-C(3) bond of the norbornene ring. The degree of involvement of both olefinic bonds of diene in alternating copolymerization is decreased when the reaction is carried out in a protic solvent (methanol). The structure of terminal groups of the copolymers depends on the nature of a bidentate ligand and acid.     

Kinetic Model and Mechanism of Hydrogenation of Unsaturated Carbocyclic Compounds Based on Norbornadiene

Kinetics and Catalysis - Liquid-phase hydrogenation of bicyclo[2.2.1]hepta-2,5-diene (norbornadiene, ND) proceeds in the presence of an industrial palladium catalyst Pd/γ-Al2O3 (PK-25) in an...     

Catalytic syntheses of polycyclic compounds based on norbornadiene-2,5 in the presence of nickel complexes: II. cyclic dimerization of norbornadiene-2,5. Kinetics and mechanism of the process

Kinetics of the cyclodimerization of norbornadiene-2,5 (NBD) is studied in the presence of a catalytic system based on bis(η³-allyl)nickel. The forms of the rate laws characterized by different reaction orders with respect to NBD are determined. The influence of temperature and solvent nature on the process is studied. The thermodynamic parameters are determined. The structure of the products is shown to be determined by the structure of intermediates. The mechanism of the process, consisting of the following main steps, is proposed: (1) the formation of Ni(NBD)₂, which is the true catalyst; (2) the reversible addition of NBD to the indicated complex, resulting in the formation of Ni(NBD)₃ and Ni(NBD)₄ η-complexes and accompanied by a change in ligand coordination; (3) the oxidative addition of coordinated NBD molecules to a nickel atom that gives five and six-membered metallacyclic intermediates; and (4) the reductive elimination of nickel from them to form cyclic dimers. The conditions for the selective formation of individual isomers are proposed.