S.D. Bhatt

Hydrogenation of alkenes and aromatic hydrocarbons using water-soluble RuCl2(TPPTS)3 in aqueous medium

Abstract Water-soluble ruthenium complex RuCl 2 (TPPTS) 3 have been used for the catalytic hydrogenation of unsaturated hydrocarbons, namely, 1-hexene, 1-heptene, styrene, cyclooctadiene, cyclooctene and benzene. Hydrogenation reactions were carried out under mild conditions. Optimum conditions for hydrogenation was evaluated and all substrate were studied at optimum conditions. The catalytic hydrogenation performances have been compared for aliphatic and aromatic hydrocarbons analogues. Results shows aliphatic hydrogenation occurs more easily compared to aromatic hydrogenation. Effect of addition of zinc chloride to aqueous solution on the hydrogenation of benzene showed that at some critical concentration of zinc chloride, partial hydrogenation of benzene to cyclohexene occurs.

Dioxygen affinities of some ruthenium(III) schiff base complexes

Abstract The synthesis and dioxygen affinities of some ruthenium(III) Schiff base complexes in DMF solution in the presence of different axial bases are reported. The ligands used are bis(salicylaldehyde)ethylenediimine (salen), bis(salicylaldehyde)diethylenetriimine (saldien), bis(picolinaldehyde)- o -phenylenediimine (picoph), bis(picolinaidehyde)ethylenediimine (picen) and bis(picolinaldehyde)diethylenetriimine (picdien). The axial ligands employed are chloride (Cl − ), imidazole (Im) and 2-methylimidazole (2-MeIm). From the oxygenation constants it is found that electron donating substituents on the Schiff bases increase the affinity for dioxygen. Equilibrium dioxygen uptake measurements at 278, 288 and 303 K provide values of Δ H ° and Δ S ° of oxygenation that fall in the range − 6.1 to −13.3 kcal mol − 1 for Δ H ° and − 10 to − 31 cal deg − 1 mol − 1 for Δ S °. The dioxygen adducts of Ru III were characterized by electrochemistry, UV–vis, IR and EPR techniques as Ru IV superoxo complexes.

Kinetics and mechanism of the epoxidation of styrene and substituted styrenes with O2 catalysed by [RuIII(EDTA)(H2O)]-

Epoxidation of styrene, 2-methylstyrene, 3-chlorostyrene and 4-methoxystyrene with molecular oxygen catalysed by [RuIII(EDTA)(H2O)]− (1a) (EDTA = ethylenediaminete-traacetate) was studied as a function of catalyst (1a), substrate and dissolved oxygen concentration in 50% water-dioxane medium. The rate of epoxidation was found to be first order with respect to complex 1a and substrate concentrations and one-half order with respect to dissolved oxygen concentration. At high substrate concentrations a zero-order dependence of rate with respect to substrate concentration was observed in each case. Stoichiometric oxidation of styrene and substituted styrenes by [RuV = O(EDTA)]− (2) was studied, and results are compared with the catalytic epoxidation reactions with molecular oxygen.

Oxygenation reactions of saturated and unsaturated substrates by molecular O2 catalyzed by the versatile catalyst K[Ru(EDTAH)Cl]·2H2O: Rate and activation studies

Abstract Oxygenation of olefinic and saturated substrates, including triphenylphosphine, with molecular oxygen is catalyzed by (ethylene-diaminetetraacetato)aquoruthenate(III) ion, [Ru III (EDTA)(H 2 O)] − 1 , in a mixed solvent medium to yield a variety of products. The wide range of products formed includes oxides, epoxides, alcohols, ketones and aldehydes. The kinetics of these oxidation reactions have been investigated by oxygen absorption methods and product analysis at pH 3.0 (μ = 0.1 M NaClO 4 ) in the temperature range 288–318 K in water—dioxane medium (1:1). In order to eliminate any radical chemical pathway with dioxane:H 2 O, the oxygenation of a few selected substrates, cyclohexane and 1-hexane was conducted in water—DMF (1:1) medium. General mechanisms are proposed for both saturated and unsaturated substrates on the basis of the kinetic data and are discussed in terms of reactivity. In all cases, a μ-peroxoruthenium(IV)—substrate complex was suggested as the active intermediate. The activation parameters corresponding to rate constants at different temperatures were computed. The activation enthalpies are much more favourable for the oxidation of PPh 3 and olefins, as compared to saturated substrates.

Kinetics and mechanisms of oxidation of triphenylphosphine with iodosylbenzene catalyzed by N-hydroxyethylethylenediaminetriacetatoruthenate(III) in water—dioxane medium

Abstract The kinetics of oxygenation of [RuIII(HEDTA)(H2O)] complex 1, where HEDTA = N-hydroxyethylethylenediaminetriacetate anion, with iodosylbenzene was studied spectrophotometrically by the stopped flow technique. The rate of formation of [RuV(HEDTA)(O)] complex 2 was monitored at the characteristic peak of the oxo complex 2 at 393 nm. Subsequent oxygen atom transfer from complex 2 to PPh3 was investigated by following the disappearance of the oxo peak at 393 nm. The rate and activation parameters (ΔH≠ and ΔS≠) for both oxygenation of complex 1 with PhIO and oxygen atom transfer from complex 2 to PPh3 were determined and the experimental results are discussed with reference to the data reported for the oxidation of PPh3 catalyzed by the corresponding EDTA—H and PDTA—H complexes.

Oxidation of tertiary phosphines by molecular oxygen catalysed by RuIII-EDTA complex. Electronic effect of phosphine substituent on the oxygen atom transfer reaction; X-ray crystal structure of the complex [RuIII(EDTA-H)PPh3]

Abstract The catalytic oxidation of tertiary phosphines, PR 3 (R = p -fluorophenyl, phenyl and cyclohexyl), by molecular oxygen to the corresponding phosphine oxide, (PR 3 O), catalysed by Ru III (EDTA-H)(H 2 O) is reported as a function of catalyst, substrate (PR 3 ) and molecular oxygen concentration at a constant pH 3.0 in water-dioxan (50% v/v) medium. The reactivity of PR 3 towards catalytic oxidation by molecular oxygen decreases in the order tris( p -fluorophenyl)phosphine triphenylphosphine tris-(cyclohexyl)-phosphine. A reverse reactivity order was observed in the case of stoichiometric oxidation of PR 3 by [ORu V (EDTA)] − . The proposed mixed-ligand complex Ru III -EDTA-PR 3 intermediate in the catalytic oxidation of PR 3 with molecular oxygen has been isolated and its structure solved by single-crystal X-ray diffraction. The experimental results are discussed in terms of the σ-basic and π-acidic character of the phosphine substrates in the homolytic bond cleavage of OO bonds of the μ-peroxo intermediate and oxygen atom transfer to the substrate. The bond dissociation energy for OO bond cleavage is computed by the kinetic data obtained for oxygen atom transfer from the oxo complex [ORu V (EDTA)] − .

Oxidation of organic substrates by molecular O2 catalyzed by dichlorotetraaquoruthenium(III) ion

Abstract Kinetic studies pertaining to oxygenation of organic substrates by molecular oxygen catalysed by dichlorotetraaquoruthenium(III) ion, [RuCl2(H2O)4]+ (1) are described. The reactions with olefins proceed through a homodioxygenase route with the transfer of both the O atoms of molecular O2 to the substrate; those with saturated substrates proceed through hydride abstraction followed by oxygen atom insertion. The kinetics of the oxidation of alkanes and olefinic substrates were investigated in H2O:dioxan:NaClO4 media in the temperature range 298–318 K. General mechanisms in conformity with the kinetic results and product analysis are proposed for the oxidation of these substrates.

Kinetics and thermodynamics of RuIII-EDTA complex catalyzed oxidation of diethylamine and triethylamine with molecular oxygen

The kinetics of oxidation of diethyl and triethylamine with molecular oxygen catalyzed by RuIII (EDTA-H) (H2O) complex has been studied at different temperatures (25–45 °C at pH 2.0 (μ=0.5 M KCl) as a function of amine concentration. The thermodynamic (ΔG0, ΔH0 and ΔS0) and the activation parameters (ΔH≠ and ΔS≠) for the reaction were computed.AbstractКинетику окисления диэтил-и триэтиламинов молекулярным кислородом, катализированного комплексом RuIII (EDTA-H) (H2O) исследовали при различных температурах (25–45°C) и pH=2 (μ=0,5 M KCI) в зависимости от концентрации амина. Рассчитывали термодинамические параметры (ΔG0, ΔH0 и ΔS0), а также параметры активации реакции (ΔH≠ иΔS≠).

Gas phase hydroformylation of propylene over supported Ru−Fe bimetallic catalysts

Bimetallic catalysts consisting of Ru−Fe prepared on SiO2 and carbon (sibunit) supports were found to be catalytically active and selective in the formation of C4-aldehydes and alcohols in hydroformylation of propylene at 433 K and 2 atm. of CO+H2+C3H6 (1∶1∶1). The addition of Fe to Ru altered the activity of monometallic Ru catalyst and favored the hydrogenation of CO to methanol.