ESR study of free radicals formed upon UV irradiation of nitropentafluoroacetone in various solvents

The formation of CF₃C(O)CF₂N(O^.)O₂CF₂C(O)CF₃ free radicals upon the UV irradiation of nitropentafluoroacetone (1) in toluene and mesitylene is established by ESR. The most likely cause of their formation is the one-electron oxidation of the solvents by photoexcited1 followed by decay of the radical anion formed from1 with the expulsion of an NO₂ anion and attachment of the radical to a molecule of original1. The irradiation of 1 in triethylsilane results in the elimination of a fluoride ion and fixation of a CF₃COCFN(O^–)O' radical. UV irradiation of ketone1 in pentane results in the abstraction of a hydrogen atom from the solvent and the formation of a CF₃COCF₂N(OH)O ' radical.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 512–514, March, 1993.     

Photochemistry of benzimidazolocyanine dyes in solvents of different polarity

The effect of ion pair formation on the kinetics of the decay of the photoisomers and triplet states of cationic benzimidazolocyanine dyes is studied by flash photolysis. An increase in the rate constant of the reversecis-trans isomerization of the photoisomers is observed when ion pairs are formed (in nonpolar solvents). In the case of benzimidazolocyanine dyes with the I^– anion, ion-pair formation causes an increase in the rate constant of decay of the triplet state. Acceleration of S₁ S₀ internal conversion is discovered for the dyes with I^–1 Translated fromIvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 507–512, March, 1993.     

The mechanism of nitrite formation in the radiation-induced oxidation of ammonia in aerated aqueous solutions

The mechanism of the radiation-induced conversion of ammonia to nitrites and nitrates in aerated aqueous solutions has been studied. The formation of the pernitrite ion, O=N-O-O^–, was detected at pH 10.5. The kinetics of its formation and decay were studied, andk _form was estimated at (2.3±0.2)·10⁷ L mol^–1 s^–1. The course of decay obeys first-order kinetics; the rate constant decreases at higher pH. Radiochemical yields of pernitrite, nitrite and nitrate at various pH and initial NH₃ concentrations were determined. A mechanism of ammonia oxidation in aqueous solution is proposed.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 280–283, February, 1993.     

Preparation and reactivity of metal-containing monomers

Thermal transformations (at 340 to 390 °C) of coprecipitates of iron and cobalt acrylates, [Fe₃O(CH₂CHCOO)₆OH][Co(CH₂CHCOO)₂]_2.4 (1) and [Fe₃O(CH₂CHCOO)₆OH][Co(CH₂CHCOO)₂]_1.5·3H₂O (2), are studied. The dependence of the degree of gas evolution () on time is described by the equation () wherek ₁=2.3 · 10¹² · exp[–49500/(RT)] s^–1,k ₂=6.0 · 10⁶ · exp[–33000/(RT)] s^–1 andk ₁=2.6 · 10¹² · exp[–49000/(RT)] s^–1,k ₂=6.6 · 10⁵ · exp[–30000/(RT)] s^–1 for cocrystallizates1 and2, respectively. The coefficient ₁ decreases as the temperature increases. The value of ₁ for compound1 is higher than that for compound2. The composition of products of the transformations of1 and2 are studied. The main solid state products of the decomposition are nanometer-sized particles of cobalt ferrite, CoFe₂O₄, with a narrow size distribution stabilized by the polymeric matrix. The thermal transformations of cocrystallizates1 and2 include dehydration, thermal decomposition, copolymerization in the solid state, and decarboxylation of the metallocarboxylate groups of the polymer. The effect of the ratio between the Fe clusters and the Co-containing fragments on the process of thermal transformation is analyzed.For Part 40, seeRuss. Chem. Bull., 1994,43, 2020.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 885–893, May, 1995.The authors are grateful to A. N. Titkov for optical microscopic and electron microscopic studies.     

Equilibrium CH-acidities of dimethyl 2-dimethoxyphosphoryl malonate and its thiophosphoryl analog

The pK _a values of dimethyl 2-dimethoxyphosphoryl malonate and of its thiophosphoryl analog have been measured by transmetallation using the inclusion complex of Li⁺ with [2.1.1]-cryptand as the metallation agent.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 410–411, February, 1993.     

Polar bonds in π-complexes. Preparation and crystal structures of cyclopentadienylcarbonyl iron(II) and ruthenium(II) benzoates andp-fluorobenzoates

Complexes of Fe(II) and Ru(II) of the general formula Cp(OC)₂MOC(O)C₆H₄X-p, where M=Fe, X=H, F (1, 2) or M=Ru, X=H, F (3, 4) have been prepared by reactingp-XC₆H₄COOAg with [CpFe(CO)₂]₂ or CpRu(CO)₂I. The crystal structures of complexes1–3 have been determined using X-ray diffraction. Compounds1 and3 are isomorphous. The COO group in1–3 is coordinated as a monodentate ligand. As the latter and the CO ligands are electronically non-equivalent, the coordination of the Cp ligand to the metal is slightly asymmetric.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 395–399, February, 1993.     

Synthesis of (methylchlorosilyl)methyldichlorophosphines

(Methylchlorosilyl)methyldichlorophosphines have been synthesized by the reaction of [dimethy(diethylamino)silyl]- or [methyl-bis(diethylamino)silyl]methylmagnesium chlorides with PCl₃ in ether at –40÷–20 °C and subsequent treatment of the reaction mixture with dry HCl. The structures of the compounds thus obtained have been studied by³¹P,¹H, and¹³C NMR spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 989–990, May, 1993.     

Reactions of heptacyclo[8.4.0.02,12.03,8.04,6.05,9.011,13]tetradecane (binor-s) with acids and alcohols catalyzed by Pd,Rh, and Pt complexes and some transformations of the compounds formed

Reactions of heptacyclo[8.4.0.0^2,12.0^3,8.0^4,6.0^5,9.0^11,13)tetradecane (binor-s)1 with proton-donor reagents were studied. Interaction of HCl and CF₃COOH with1 (25°C, 9–18 h) occurs at the cyclopropane ring (CPR) with regioselective cleavage of the C(4)–C(5) bond. With an excess of a proton-donor reagent the second CPR, whose opening proceeds nonselectively at both the C(11)–C(12) and C(11)–C(13) bonds, enters the reaction. The addition of MeOH and AcOH to1 proceeds only on boiling in the presence of such catalysts as PdCl₂, RhCl₃, and H₂PtCl₆. The chloro-, acetoxy-, methoxy-, dichloro-, and bistrifluoroacetoxy-derivatives (yields up to 95 %) were characterized by their¹³C NMR spectra.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 728–732, April, 1993.     

Interaction of iron carbonyls with Lewis bases

The interaction of iron carbonyls Fe _n (CO) _m (wheren = 1,m = 5;n = 2,m = 9;n = 3,m = 12) with anionic Lewis bases (H^–, F^–, Cl^–, Br^– , I^–, CN^–, SCN^–, N₃ ^–, MeSO₃ ^–, MeCO₂ ^–, CF₃CO₂ ^–, S₂ ^–, CO₃ ^2–, and SO₄ ^2–) passes through two-stage redox-disproportionation. The first stage is the formation of an iron carbonyl-base complex, [Fe _n (CO) _m–1C(O)L]^–, and the second is a single-electron reduction of this complex by another molecule of the initial iron carbonyl, giving rise to Fe(l) and Fe(–l) derivatives.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 248–249, January, 1996.     

Cationic polymerization of hydrocarbon monomers under the action of acyl halide complexes with Lewis acids

Polymerization of isobutylene in hexane at –78 °C under the action of the complex AcBr · 2AlBr₃ (Ac-2) affords polyisobutylene having C=O groups at the head and C-Br or C=C groups at the tail of all the molecules. The presence of the latter indicates that there occurs proton elimination from the growing carbocation with the formation of a superacid HBr · 2AlBr₃ which is unable to initiate the polymerization repeatedly under given contitions. This makes it possible to consider proton elimination as the reaction of the decay of active centers with the rate constantk _d. This value has been calculated from the rate of accumulation of the polymeric molecules having terminal C=C bonds:k _d=3.5 · 10^–4 s^–1. The rate constant of chain growthk _g has been determined from polymerization kinetics and from the content of active centers:k _g=6.2 L mol^–1 s^–1.For part 3, see ref. 4.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 883–886, May, 1993.     

Kinetics and mechanism of thermal decomposition of hydroxylammonium nitrate

The kinetics of thermal decomposition of melted hydroxylammonium nitrate have been investigated by the rate of heat production in the temperature range 84.8–120.9°C. The decomposition proceeds with autocatalysis and up to 60 % of conversion the rate of the process increases proportionally to the square of the degree of decomposition. The initial rate is proportional to the square of the concentration of HNO₃ formed due to dissociation of the salt. The activation energy of this process is 15.3±1.8 kcal/mol. It is suggested that the initial stage the process proceeds via interaction between N₂O₃ and NH₃OH⁺, whereas the subsequent acceleration is due to oxidation of NH₃OH⁺ by nitrogen oxides formed as well as by nitrous acid.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1897–1901, November, 1993.     

Rate constant of the recombination of free electrons and holes in AgCl at 295 K

The transient kinetics of the loss of electrons generated by light pulses in powdered AgCl has been studied by the microwave photoconductivity method (36 GHz) at 295 K. At high light intensities,I ₀ > 10¹⁴ photon cm^–2 per pulse, the kinetics obeys the second-order law. The rate constant of the recombination of free electrons and holes is equal to 2·10^–12 cm³ s^–1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2234–2236, September, 1996.     

Catalytic synthesis and transformations of magnesacycloalkanes

Catalytic cyclometallation of bicyclo[2.2.1]hept-2-ene, spirocyclo[2.2.1]hept-2-ene-7.1'-cyclopropane andendo-tricyclo[5.2.1.0^2,6]deca-3,8-diene (dicyclopentadiene) with R₂Mg (R =n-Pr,n-Bu) leading to the formation of polycyclic magnesacyclopentanes (MC) has been studied. The yield of MC and the selectivity of the reaction have been shown to depend on the ratio of starting reagents, the solvent, and temperature. The most probable scheme of the transformation studied is proposed.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 165–169, January, 1993.     

Quenching excited triplet C60 fullerene by tetracyanoethylene in benzonitrile

Quenching excited triplet³C₆₀ fullerene by tetracyanoethylene (TCNE) in a benzonitrile solution proceeds with a rate constant equal to (4.2±0.3) · 10¹⁸ (M · s)^–1. The formation of a radical ion pair [C₆₀ ⁺ · · · TCNE^–] was observed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1228–1230, July, 1993.     

Preparation and reactivity of metal-containing monomers.

The thermal decomposition of Cu^II, Co^II, Ni^II, Mn^II, Fe^III, and Cr^III methacryloylacetonates has been compared with the thermal behavior of the corresponding acetylacetonates and poly (methacryioylacetonates). Dehydration and thermal polymerization of methacryioylacetonates occur at 110–160 °C. The results of the thermolysis conform with the Irving-Williams sequence for the stability of the complexes of bivalent transition metals. Thermal destruction of metallopolymers differs from that of low-molecular analogs. The temperature of complete decomposition of the compounds studied correlates with the number of electrons in the d-orbital of the metal.For part 35 seeRuss. Chem. Bull., 1993,42, 1972.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 43–47, January, 1994.     

Thermal stability and crystal structure of potassium fluoride monoperoxosolvate KF·H2O2

Potassium fluoride peroxosolvate KF-H₂O₂ was obtained upon action of a 30% aqueous solution of hydrogen peroxide on solid potassium fluoride dihydrate. As compared to other peroxosolvates, KF-H₂O₂ is characterized by the highest thermal stability: the decomposition rate constantk ₁, at 120°C is 1.4 10^–3 min^–1, the enthalpy of H₂O₂ addition to KF is 8.1 kcal/ mol. The correlation between the high stability of KF-H₂O₂ and the absence of catalytic properties of KF towards H₂O₂, and the formation of strong intermolecular O-H...F and intramolecular O-H...O hydrogen bonds in the crystal is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 38–44, January, 1993.     

Heterogeneous microporous structures and adsorption properties of carbon adsorbents

A theoretical basis for calculating parameters of the pore structure of active carbons is considered. Active carbons are classified into four types according to their dispersion and mesopore surface areas. The parameters of micro- and mesopores of active carbons produced in different countries have been determined from benzene vapor adsorption isotherms at 293 K. The differences in parameters of the Dubinin—Stoeckly equation found from adsorption isotherms of different compounds are noted.For part 11, seeIzv. Akad. Nauk SSSR, Ser. Khim., 1990, 2691 [Bull. Acad. Sci. USSR, Div. Chem. Sci., 1990,39, 2438 (Engl. Transl.)].Deceased July 13, 1993.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1373–1376, August, 1993.     

Recent studies on phosphorus-bridging carbonyl derivatives: organophosphorus analogs of aldehydes and ketones

Reactions of disodium tetracarbonylferrate, Na₂Fe(CO)₄, with sterically hindered dialkylaminodichlorophosphines, R₂NPCl₂ (R₂N=diisopropylamino, dicyclohexylamino, and 2,2, 6, 6-tetramethylpiperidino) in diethyl ether lead to the air-stable phosphorus-bridging carbonyl derivatives (R₂NP)₂COFe₂(CO)₆ as the major products. The phosphorus-bridging carbonyl group in (i-Pr₂NP)₂COFe₂(CO)₆ has been found to undergo the following types of reactions: 1)Reduction, 2)Acylation, 3)Extrusion of the carbonyl group. The mechanisms of the reactions have been considered.This work was presented at the Workshop «The Modern Problems of Heteroorganic Chemistry» held on the ship «Nikolai Bauman» during the period May 8–13, 1993.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1858–1867, November, 1993.     

Hindered rotation of ligands in cis-[PtR2Cl2] complexes

The temperature dependence of the¹H NMR spectra ofcis-[Pt(II)R₂Cl₂] complexes was studied in DMSO at 18–100°C (R is 2-methyl and 2,5-dimethylpyridine). The broadening of the signals from the methyl groups or hydrogen atoms in theortho-positions of heteroaromatic ligands is due to the coexistence of two forms of thecis-complexes in solution. These forms arise from the hindered rotation of asymmetrical ligands around the Pt-N bond.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 424–425, February, 1993.     

Studies of the compositions of Pd(II) hydrolysis products

The characterization of the clusters formed on alkaline hydrolysis of [PdCl₄]^2– was performed using¹⁷O,²³Na,³⁵Cl,¹³³Cs NMR and UV spectroscopy. The chemical composition of the clusters was found to be [Pd(OH)₂] _n ·nNaCl. No mononuclear oxo- or hydroxocomplexes were detected. The spatial structure of the clusters is stabilized by alkali metal cations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 675–679, April, 1993.