A physico-chemical study of iron-chromium-molybdenum catalysts

In the study of the Fe_1–xCr_xMo_1·5O₆ system by X-ray, IR and Mössbauer methods the formation of solid state substitution solutions has been detected, which possess similar catalytic properties in methanol oxidation.

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, , Fe_1–xMo_1·5O₆ , .

     

Interaction of phosphomolybdovanadium heteropolyacids with hydrazine hydrate studied by a calorimetric method

The heats of interaction of VO ₂ ⁺ and of heteropolyacids H_3+nPMo_12−nV_nO₄₀ (n=1,2,3,6) with N₂H₄ have been measured.

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Измерены теплоты взаимодействия VO ₂ ⁺ и гетерополикислот H_3+nPMo_12−nV_nO₄₀ (n=1,2,3,6) с N₂H₄.

     

Mössbauer study of thermal decomposition of the [FeCp(SPh)CO]2 complex and its reaction with the surface of activated silica gel

Thermal decomposition of the [FeCp(SPh)CO]₂ complex and its reaction with the surface of activated silica gel were investigated by Mössbauer spectroscopy. A small amount of a complex with properties similar to ferrocene is separated in the first stage of thermal decomposition (120–130°C). The starting carbonyl complex totally disappears in the second stage (165–210°C), and two compounds are present among the products: a derivative of ferrocene and the final product, an x-ray amorphous, iron-containing structure with an ionic-covalent type of chemical bond (CB) and a 25 and 5 wt. % concentration of oxygen and sulfur, respectively. The Mössbauer parameters of this product and the compound formed in the reaction of [FeCp(SPh)CO]₂ with the surface of activated silica gel at 4.2–300 K are identical. The analysis of the data suggested that both structures are highly disperse clusters of iron oxide with the structure of an inverted spinel with superparamagnetic properties.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 771–778, April, 1991.We would like to thank Yu. B. Kopylovskii for assistance in processing the spectra with the MESLIN program.     

New Catalytic Reactions in the Presence of Mo-V-Phosphoric Heteropoly Acid Solutions

The possibility of performing new catalytic reactions in the presence of solutions of H _x+3PMo_12−x . V_xO₄₀ Mo-V-phosphoric heteropoly acids was examined.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 5, 2005, pp. 772–778.Original Russian Text Copyright © 2005 by Zhizhina, Simonova, Russkikh, Matveev.     

Reactions of Aluminium Tribromide with Tetrakis(triphenylphosphine)nickel(0) and Tetrakis(triethylphosphite)nickel(0) Complexes

Reactions of aluminium tribromide with the Ni(0) phosphine and phosphite complexes are studied by EPR method. AlBr₃was found to cause the oxidation of the transition metal in the (PPh₃)₄Ni complex to the univalent state with the formation of the tetracoordinated (PPh₃)₃NiBr complex. With an excess of AlBr₃, the phosphine ligands are eliminated from the coordination sphere of Ni(I), and the coordinatively unsaturated complexes are destroyed to give the colloidal nickel. In the reaction of (P(OEt)₃)₄Ni with AlBr₃, Ni(0) is also oxidized to Ni(I), but the acido ligand is not eliminated even with a 15-fold excess of the Lewis acid. The activity of catalytic systems on the basis of the Ni(0) phosphine complexes and the Lewis acids in the low-molecular oligomerization reactions of olefines is determined by the cationic coordinatively unsaturated Ni(I) complexes formed in these systems.     

Oxidative coupling of 5-membered heterocycles catalyzed by a Pd(II)-heteropolyacid system in dimethylformamide

Oxidative coupling of thiophene and 2-methylfuran to the corresponding dihetaryls in DMFA medium occurs in the presence of the homogeneous catalytic system Pd(II)-molybdovanodophosphoric heteropolyacid (HPA). The data obtained show that HPA may act as a reversible oxidant in polar aprotic media.

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, Pd(II)- 2- . , .

     

Catalytic oxidation of octene-1 in the presence of palladium(II) salts and heteropolyacids

In the presence of the catalytic system (PdSO₄+HPA), where HPA=H₉PMo₆V₆O₄₀, octene-1 is found to be selectively (95%) oxidized to octanone-2. The optimum concentration ratio for catalyst stability is [HPA]:[PdSO₄]=30–40. The substitution of PdCl₂ for PdSO₄ leads to the formation of all three isomeric octanones without decrease of the overall selectivity. Effective rate constants and the apparent activation energy have been determined in the temperature range from 60 to 80 °C.

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(PdSO₄+), =H₉PMo₆V₆O₄₀, -1 ( 95%) -2. []:[PdSO₄]=30–40. PdSO₄ PdCl₂ . 60–80 °C.

     

Differential-difference evolution equations. II (Darboux transformation for the Toda lattice)

Toda lattice equation is represented in the form of the condition of compatibility of the system of linear equations corresponding to a non-Hermitian Lax representation. The Darboux invariance of this linear system is defined and proved in the text, and enables us to construct some new formulas for the solutions of the Toda lattice equation. These formulas involving determinants are applicable to an arbitrary initial solution of the Toda equation for example to a solution growing at infinity.Physique Mathématique et Théorique, Equipe de recherche associée au CNRS.This work has been done as part of the program Recherche Cooperative sur Programme No. 264: Etude interdisciplinaire des problèmes inverses.Leningrad State University, U.S.S.R.