V. Z. Sharf

Catalytic reduction of aromatic dinitro compounds

The liquid-phase catalytic hydrogenation of 3,5-dinitrophenyl phenyl ether to give 3,5-diaminophenyl phenyl ether in the presence of Group VIII metals as catalysts has been investigated. The main kinetic characteristics of the process have been established. The reduction occursvia the formation of 5-amino-3-nitrophenyl phenyl ether. In terms of their activity, the catalysts studied can be arranged in the following sequence: 1% Pd/Sibunit> 2 % Pd/C > Lindlare Pd > 5% Ru/Sibunit > Raney Ni. The selectivity of the process with respect to intermediate 5-amino-3-nitrophenyl phenyl ether depends on the relative adsorption abilities of mono- and dinitro compounds. A promoting effect of water during hydrogenation of 3,5-dinitrophenyl phenyl ether in isopropanol or 1,4-dioxane has been noted. Catalytic synthesis of 3,5-diaminophenyl phenyl ether has been carried out for the first time.

Structure and catalytic activity of supported metal complexes. Communication 2. Synthesis of rhodium complexes on silica gel modified by phosphorus- and nitrogen-containing ligands

Conclusions1.Silica gel has been modified by aminophosphine groups and rhodium complexes immobilized on it: [RhCl(COD)]2, RhCl(PPh3)3, and RhCl3. IR spectroscopy was used to follow the formation of aminophosphine groups on the surface of the silica gel as the γ-aminopropyl silica reacted with the Ph2PCl.2.Using IR spectroscopy and GLC it has been shown that bonding of [RhCl(COD)]2 on a γ-aminopropyl-containing silica gel proceeds without replacement, while on the γ-aminophosphino-propyl-containing silica gel, the cyclooctadiene ligand is replaced. When complexes become bound to the latter support, the rhodium atom coordinates through the phosphorus atom of the aminophosphine group; the extent to which the nitrogen participates depends on the identity of the type of compounds immobilized.3.The activity and selectivity exhibited by the catalysts obtained in the conversion of the allylbenzene depends on the nature of the bonded ligand and the starting complex, the degree of ligand exchange, and the properties of the solvent.

New method for catalyst preparation based on metal-organic framework MOF-5 for the partial hydrogenation of phenylacetylene

Small (less than 2 nm) Pd nanoparticles immobilized in the matrix of the microporous phenylenecarboxylate metal-organic framework MOF-5 were prepared for the first time by the fluid method. The catalytic properties of samples Pd@MOF-5 were studied in the selective hydrogenation of phenylacetylene to styrene (methanol, 20 °C, PH2 = 1 atm). The catalytic experimental data and results of physicochemical studies indicate that palladium nanoparticles are mostly localized in pores of the composite material 1%Pd@MOF-5 obtained by the fluid synthesis. The specific positions of active sites in the intracrystalline volume results in the suppression of the undesirable conversion of styrene to ethylbenzene.

Structure and catalytic activity of metallocomplexes immobilized on supports 4. Heterogenized complexes of Rh(II) in reactions of hydrogenation and hydrogen transfer

Acetate, acetonitrile, sulfate, and hexafluoroacetylacetonate binuclear complexes of Rh(II) have been heterogenized on γ-aminopropyl-containing silica gel and on polymers containing 3(5)-methylpyrazole and imidazole groups. Possible paths of surface structure formation have been examined. It has been shown by means of EPR spectrometry, x-ray photoelectron spectroscopy, and electronic spectroscopy that when [Rh2(CO2CCH3)4] is deposited on γ-aminopropylcontaining silica gel and on polymers, the binuclear structure and the degree of oxidation of the metal remain unchanged. Heterogenization of the sulfate, acetonitrile, or hexafluoroacetylacetonate binuclear complexes of Rh(II) takes place with rupture of the Rh-Rh bond and an increase in the degree of oxidation of the central atom. The immobilized complexes manifest activity in allylbenzene hydrogenation and isomerization and also in the reaction of hydrogen transfer from 2-propanol to cyclohexanone. It has been shown that the complexes containing Rh(II) manifest higher activities in these reactions in comparison with the Rh(III) complexes.

Structure and catalytic activity of metallocomplexes immobilized on carriers

Mono-, bi-, and trinuclear Ru complexes with various ligands immobilized on the surface of silica gels modified with γ-aminopropyl, formamide, sulfide, cyano, or mercapto groups, catalyze hydrodehalogenation ofp-bromotoluene by the transfer of hydrogen from NaBH4 in 2-propanol both in an Ar atmosphere and in air. The structures of the heterogenized metallocomplex catalysts prepared (the nature of the ligand environment, the oxidation number of the central atom) were studied by IR and XP spectroscopy. The immobilized binuclear RuII,III tetraacetate, which retains the structure of the original complex, exhibits higher catalytic activity in the hydrogenolysis ofp-bromotoluene than heterogenized mononuclear systems.

Structure and catalytic activity of metal complexes fixed on carriers. Hydrodehalogenation of p-bromotoluene with chemically bonded hydrogen, catalyzed by immobilized rhodium(II) complexes

The structure of Rh(II) complexes with vigorous ligands immobilized on γ-aminopropyl-containing silicagel (γ-AMPS) and polymers containing 3(5)-methyl-pyrazole and imidazole groups, was investigated. It was shown by IR spectroscopy that the ligand surroundings are maintained after application only for the Rh(II) acetate complex. For the acetonitrile and hexafluoroacetylacetonate complexes there is a replacement of the ligands by amino groups of the carrier. [Rh2(O2CCH3)4] is significantly more active than other metal complexes immobilized on γ-AMPS in the hydrodehalogenation of p-bromotoluene by transfer of hydrogen from NaBH4 and propanol-2.

Structure and catalytic activity of metal complexes on carriers 3. Rhodium complexes on modified polymers and their catalytic properties in the reduction of nitrobenzene by chemically bound hydrogen

Heterogenized catalysts based on rhodium complexes attached to polymers modified by the groups 3(5)-methylpyrazole, imidazole and benzimidazole have been synthesized. The process of their formation has been investigated by IR, UV, and EPR spectroscopy. Results have been obtained for the catalytic activity of the complexes in the hydrogenation of nitrobenzene by hydrogen transfer from propan-2-ol and NaBH4.

Catalytic properties of binuclear rhodium(II) complexes in hydrogenation and isomerization of allylbenzene

Binuclear hexafluoroacetylacetonate complexes of Rh(II) with axial ligands (Py, H2O) exhibit activity in hydrogenation and isomerization of allylbenzene, and the isomerization reaction also takes place in an atmosphere of Ar. The catalytic system [Rh2(hfacac)4(H2O)2]-Ph3P is much more active than Rh(II) hexafluoroacetylacetonate complexes in transformation of allylbenzene. Treatment of the acetate complex [Rh2(O2CCH2)4] with sodium borohydride significantly increases its activity, probably due to the formation of [Rh2(O2CCH3)3]+ and [Rh2(O2CCH2)2]2+ complexes.

Study of the catalytic activity of metal complexes on solid supports. 5. Immobilized rhodium complexes in hydrogen transfer from 2-propanol to ketones and olefins

Conclusions1.Rhodium complexes [RhCl(COD)]2, RhCl(PPh3)3, and RhCl3 immobilized on silica gel modified by aminophosphine groups catalyze the transfer of hydrogen from 2-propanol to cyclohexanone, styrene, and 2-cyclohexenone and the isomerization of allylbenzene in an argon atmosphere.2.The reduction of cyclohexanone to cyclohexanol is promoted by alkali. The reaction rate is proportional to the amount of catalyst, 2-propanol concentration, and cyclohexanone. The reaction rate decreases at high ketone concentrations.3.Styrene is reduced to ethylbenzene extremely slowly. Under these conditions, allylbenzene is not reduced, but rather undergoes isomerization with the predominant formation of trans-propenylbenzene.4.The reduction of 2-cyclohexenone to cyclohexanol occurs by the initial reduction of the C=C bond and the subsequent reduction of the C=O group.

NMR study of diastereoisomerism of 2-(1-aminoethyl)bicyclo[2.2.1]heptane and its hydrochloride (deitiforin)

The assignment of the signals for the H and C atoms of four diastereomers (without their separation) of 2-(1-aminoethyl)bicyclo[2.2.1]heptane (1) and its hydrochloride (2) (the antiviral drug deitiforin) was performed for the first time by two-dimensional 1H and 13C NMR spectroscopy. The effects of the substituent at position 2 of norbornane on the chemical shifts of the α-, β-, and γ-carbon atoms of the bicycle were examined using the increments for alkanes. The changes in the chemical shifts of the C(6) and C(7) atoms are substantially larger than those for the other C atoms, which made it possible to identify the exo and endo forms. Each of these forms exists as a mixture of two diastereomers. The effect of the positive charge of the N atom on the γ-protons, which are closely spaced, but separated by a number of covalent bonds, was considered on going from amine 1 to hydrochloride 2. Based on significant changes in shielding of these H atoms, the configurations of the asymmetric center in the CHMe(NH2) substituent of the diastereomers were established.