Products of the catalytic liquid-phase oxidation of 3-carene

The liquid-phase oxidation of 3-carene in the presence of various catalytic systems has been studied. The possibility has been shown of the directed preparation of 3-carene oxide, of ketones with a carane skeleton and a 7-membered ring, or of aromatic tertiary alcohols.Institute of Physical Organic Chemistry, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 328–334, May–June, 1991.     

Aerobic oxidation of substituted phenols catalysed by metal acetylacetonates in the presence of 3-methylbutanal

The aerobic oxidation of substituted phenols with the catalytic system M(acac)_n/3-methylbutanal/O₂ has been investigated. Co(acac)₂ and Mn(acac)₃ promoted the transformation of 2,6-dimethylphenol and 2,6-di-t-butylphenol into their corresponding diphenoquinones and benzoquinones. In the oxidation of 2,3,6-trimethylphenol, the same catalysts yielded 32–34% of the relevant biphenol. Cu(acac)₂ converted 2-naphthol into 1,1′-bi-2-naphthol with 84% yield. Supported Co(II) and Cu(II) complexes have also been used as heterogeneous catalysts for the oxidation of 2,6-di-t-butylphenol and 2-naphthol, respectively.     

Discrimination of active palladium sites in catalytic liquid-phase oxidation of benzyl alcohol

Knowledge of the structure of active sites is a prerequisite for the rational design of solid catalysts. Using site-selective blocking by CO and isotope labeling combined with in situ attenuated total reflection infrared (ATR-IR) spectroscopy, we were able to discriminate the different sites involved in the liquid-phase oxidation of benzyl alcohol on Pd/Al(2)O(3). The main reaction, that is, the oxidative dehydrogenation of the alcohol to the corresponding aldehyde, showed only little dependence on structure and occurred on all exposed Pd faces, whereas the undesired product decarbonylation occurred preferentially on hollow sites on (111) Pd faces. This explains why specific blocking of the latter sites, as realized in the industrially used Pd-Bi/Al(2)O(3) catalysts, leads to improved catalytic performance.     

Acid-base properties of the surface of chromatographic sorbents modified by metal acetylacetonates

The acid-base properties of metal acetylacetonates and chromatographic sorbents on the basis of Chromaton N with deposited combined stationary phases from polyethylene glycol (PEG 20M) and nickel(II) and iron(III) acetylacetonates have been investigated by means of pH measurement and Hammett indicator adsorption. The change of the acid-base state of the surface of Chromaton N depending on the nature of a metal of the modifying additive, the complex structure, and the deposition method has been demonstrated.     

Physicochemical properties and catalytic activity of metal tetraphenyl porphins in the oxidation of alkylaromatic hydrocarbons

We consider the effect of complexing metal in a tetraphenylporphin molecule on its catalytic activity in oxidizing alkylaromatic hydrocarbons by molecular oxygen. The catalytic activity of metal porphyrins (Co, Cu, Zn, Mn, and In TPP) is found to depend on their oxidation potentials and the distribution of electron density in the molecule. The electron-donating compound imidazole is shown to affect the oxidation rate.     

Correlation between structure and catalytic activity of manganese oxides in liquid-phase oxidation of 1-octene

We have studied the correlation between the crystal structure and the catalytic activity of manganese oxides MnO, MnO₂, Mn₃O₄, and Mn₂O₃ in liquid-phase oxidation of 1-octene by molecular oxygen. The catalytic activity decreases in the series of oxides with octahedral coordination environment for the manganese atoms MnO−Mn₂O₃−MnO₂. The oxide Mn₃O₄ (with mixed tetrahedral and octahedral environment for the Mn atoms) catalyzes the process according to a different mechanism. L'vov Polytechnic State University, 12 S. Bandery ul., L'vov-13 290646, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 34, No. 5, pp. 324–327, September–October, 1998.     

Thermolysis of binuclear heterometallic pivalate with Pd(II)-Ce(III) metal core in dibenzyl ether

A reaction between palladium(II) acetate and aqueous cerium(III) acetate in acetic acid with subsequent boiling in benzene with excess pivalic acid is found to yield the complex Pd(μ-OOCBu^t)₄Ce(OOCBu^t)(HOOCBu^t)₃ (1). The liquid-phase thermolysis of complex 1 in dibenzyl ether (190°C) leads to the formation of the tetranuclear complex [Pd(μ-OOCBu^t)₄Ce(HOOCBu^t)]₂(μ-OOCBu^t)(μ-OH₂) (2). The structure of the synthesized complexes is established by X-ray diffraction.     

Diffusion coefficients of metal acetylacetonates in supercritical carbon dioxide

Binary diffusion coefficients, D₁₂, of the metal acetylacetonates, palladium(II) acetylacetonate and cobalt(III) acetylacetonate, were measured from 308.2 to 343.2 K over the pressure range from 9 to 40 MPa at infinite dilution in supercritical carbon dioxide using the chromatographic impulse response method. The effects of pressure, temperature, density, and viscosity on D₁₂ values were examined. It was observed that the D₁₂ values of palladium(II) acetylacetonate and cobalt(III) acetylacetonate were larger than those of lipids with similar molecular weights, such as arachidonic acid and monoolein, respectively. Furthermore, the measured D₁₂ data of each metal acetylacetonate were well correlated by the hydrodynamic equation D₁₂/T as a function of carbon dioxide viscosity.     

Features of intermolecular interactions in the crystals of metal acetylacetonates

For 12 acetylacetonates of the composition M(acac) _n (n = 2, 3, or 4) and M(acac)(C₂H₄)₂ (M is a metal) the total area (⁰ S) of the faces of Voronoi-Dirichlet polyhedra (VDP) corresponding to all intermolecular contacts of one molecule in the crystal structure and the total volume of pyramids (⁰ V), whose bases are formed of such faces and the vertices are occupied by the nuclei of atoms participating in intermolecular contacts, are determined. The key features of non-bonded interactions are considered. The existence of a linear dependence of the sublimation enthalpy of acetylacetonates on the ⁰ S or ⁰ V parameters of their molecular VDP is revealed. It is shown that the sublimation enthalpy of Ga(acac)₃ requires the refinement and theoretically should be 124 kJ/mol.     

The metal complexes of new Schiff bases containing phosphonate groups and catalytic properties for alkane oxidation

In this study, two new salicylidene phosphonate ligands (HL¹ and HL²) and their metal complexes (Cu²⁺, VO²⁺ and La³⁺) were synthesized and characterized by spectroscopic and analytical methods. The molecular structure of the ligand HL¹ was determined by single‐crystal X‐ray diffraction study. In the structure of the ligand, there is an intramolecular phenol‐imine hydrogen bond. The synthesized compounds exhibit only one emission maximum upon excitation at 270–295  nm range. Complexation of the Schiff base ligands with metal ions did not cause a considerable quenching effect. Finally, the complexes prepared were used as catalysts in cyclohexane oxidation under microwave irradiation. The complexes showed high conversion rates (> 90%) for cyclohexane oxidation; however, poor selectivity was observed for all complexes. The La³⁺ complexes showed better selectivity for cyclohexane → cyclohexanol transformation with about 45% selectivity.     

Polyfunctional activity of metal complexes containing 2,6-Di-tert-butylphenol in catalytic oxidation

The results of the investigations of metal complexes containing 2,6-di-tert-butilphenol in the ligand environment in catalytic homogeneous oxidation of organic compounds are reviewed. The liquid-phase oxidation of hydrocarbons, olefins, aminophenol and unsaturated fatty acids by molecular oxygen in the presence of phthalocyanines, porphyrins, σ-aryl and π-allyl transition metal complexes is described. The change of the reactivity of organometallic and coordination compounds by oxidation of the redox active phenolic group opens up the possibility to use them as polyfunctional catalytic systems showing positive and/or negative catalytic effects.     

A mathematical model of the regeneration of the catalytic solution in the liquid-phase oxidation of unsaturated hydrocarbons

The study describes the mathematical model, calculation and optimization of the technological scheme of the regeneration of the catalytic solution in the liquid-phase oxidation of hydrocarbons.

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Effect of technique of applying layers of metal acetylacetonates on acid-base and chromatographic properties of sorbents

A series of chromatographic sorbents, which differ by way of applying modifying chelates of acetylacetone was obtained. The acid-base and chromatographic properties of sorbents with thermally and chemically grafted layers of metal acetylacetonates were investigated. It was shown that the modifi cation of the mineral sorbents with metal acetylacetonates leads to a change in the surface acidity, as well as to an increase in the polarity and selectivity with respect to different classes of compounds.     

Homogeneous catalytic oxidation of pyrocatechol in the presence of transition metal ions

Pyrocatechol oxidation by oxygen in aqueous solutions containing different metal ions, proceeds via the intermediate formation of pyrocatechol-metal ion-oxygen complexes, Catalytic activity of metal ions depends on their donor-acceptor properties.

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Magnetic properties of new complexes of 3d metal chlorides with 3-amino-4-ethoxycarbonylpyrazole

New complexes of Co(II), Ni(II), and Cu(II) chlorides with 3-amino-4-ethoxycarbonylpyrazole (L) of the composition ML₂Cl₂ are synthesized. The compounds are studied by powder X-ray diffraction, electronic and IR spectroscopy, static magnetic susceptibility (temperature range 2–300 K). It is found that in the ML₂Cl₂ complexes (M = Co(II), Ni(II), Cu(II)) ferromagnetic exchange interactions between the unpaired electrons of metal ions occur. In [CoL₂Cl₂] and [NiL₂Cl₂] compounds a transition to the magnetically ordered state (T _c ? 10–12 K) is observed.