Debabrata Chatterjee

Properties and reactivities of polyaminopolycarboxylate (pac) complexes of ruthenium

Abstract The development and intriguing aspects of the chemistry of Ru—pac (pac = polyaminopolycarboxylate) complexes are reviewed in this article. Kinetics and mechanistic aspects of Ru—pac complexes towards substitution reactions are discussed with reference to the role of the uncoordinated pendant group of the pac ligands in the remarkable lability of Ru pac complexes towards the aquo-substitution process. The catalytic ability of Ru pac complexes in various organic transformations are highlighted, along with the mechanistic details. The recent development of electrocatalytic systems with Ru—pac complexes for activation of small molecules is addressed. Most current investigations on the mixed-ligand complexes of ruthenium-containing pac ligands are included in this article. Applications of these mixed-ligand complexes to some biochemical processes or in developing new inorganic materials are discussed.

First report on highly efficient alkene hydrogenation catalysed by Ni(salen) complex encapsulated in zeolite

Ni(salen) (salen = bis-(salicylidene)ethylenediamine) complex was encapsulated in zeolite Y and hydrogenations of cyclohexene, cyclooctene, 1-hexene and benzene were carried out with Ni(salen) encapsulated zeolite at moderately high temperature (40°C) and pressure (60 atm of H2).

Photocatalytic reduction of N2 to NH 3 sensitized by the [RuIII-ethylenediaminetetraacetate-2,2′-bipyridyl]− complex in a Pt-TiO2 semiconductor particulate system

Abstract The complex K[RuIII(EDTA)(bipy)] (where EDTA denotes ethylenediaminetetraacetate, and bipy denotes 2,2′-bipyridyl) was synthesized and characterized. The photophysical properties of this complex were studied and its application as photosensitizer in the photoreduction of N2 to NH3 in a Pt-TiO2 semiconductor particulate system is reported.

Charge type effects on the temperature dependence of intervalence transfer in ferrocyanide substituted ruthenium(III) amine and aminopolycarboxylate compounds

Abstract The K4[RuIII(hedtra)NCFeII(CN)5] (3) (hedtra=N-hydroxyethylethylenediaminetriacetate) complex has been synthesised and characterised by physicochemical analysis. The temperature dependence of intervalence transfer in 3 has been studied and compared with that observed in [RuIII(edta)NCFeII(CN)5]5− (1) and [RuIII(NH3)5NCFeII(CN)5]− (2), complexes. The charge type on the ruthenium centre of the binuclear complexes has been found to effect the intervalence thermochromism. This has been discussed in terms of a charge type effect on the temperature dependency of ΔE (vibrationally relaxed initial state/final state separation energy) and the χ (reorganisation energy) component of EIVCT (intervalence charge transfer energy).

Kinetics and mechanism of epoxidation of cyclohexene and cyclooctene with potassium hydrogen persulphate catalyzed by aquoethylenediaminetetraacetatoruthenate(III) complex ion in water-dioxane medium

Abstract The kinetics of oxygenation of [(EDTA)Ru III (H 2 O)] − to [(EDTA)Ru v (O)] − by KHSO 5 was studied spectrophotometrically by following the appearance of characteristic peak of [(EDTA)Ru v (O)] − (ϵ 393 max = 8000) at a fixed pH of 6.0 and ionic strength 0.2 M (NaCiO 4 ). The time course of subsequent oxygen transfer from [(EDTA)Ru v (O)] − to cyclohexene and cyclooctene was investigated by following the decrease in the characteristic oxo peak at 393 nm as a function of substrate concentration and temperature (30–50 °C) at a constant pH of 6 and ionic strength 0.2 M (NaC1O 4 ). Activation parameters for both the oxygenation of [(EDTA)Ru III (H 2 O)] − to [(EDTA)Ru v (O)] − and oxygen atom transfer from [(EDTA)Ru v (O)] − to cyclohexene and cyclooctene were determined and probable mechanisms for both reactions proposed.

Selective air oxidation of dimethyl sulfide to dimethyl sulfoxide catalysed by aminopolycarboxylatoruthenium(III) complex

Abstract Reactions of Ru III L(H 2 O) (L = aminopolycarboxylate ligands viz. edta, pdta, hedtra) with dimethylsulfide (DMS) and dimethylsulfoxide (DMSO) were studied by using spectrophotometric, electrochemical and kinetic methods. [Ru III L(DMS)] complexes formed by the interaction of Ru III L(H 2 O) and DMS undergo oxidation when exposed to air to yield DMSO and Ru III L(H 2 O) back. Under identical condition [Ru III L(DMSO)] complexes do not undergo any further oxidation to produce dimethyl sulfone.

Photosensitized reduction of N2 by RuII(bipy)32+ adsorbed on the surface of Pt/TiO2/RuO2 semiconductor particulate system containing RuIII-EDTA complex and L-ascorbic acid

Photocatalytic reduction of N2 to NH3 was carried out in a surface-modified semiconductor particulate system containing Pt/TiO2/RuO2 semiconductor powder, K[RuIII(EDTA-H)Cl]-(EDTA-H = anion of ethylenediaminetetracetic acid) complex as a catalyst and L-ascorbic acid as a sacrificial electron donor. The surface of the Pt/TiO2/RuO2 semiconductor was modified by adsorbing photoactive RuII(bipy)32+ complex. Illumination of the system containing N2, surface-modified semiconductor, RuIII-EDTA complex and ascorbic acid at the photoexcitation energy of RuII(bipy)32+ (510 nm) produces appreciable amounts of NH3 with a turnover rate of 1.13 mol NH3 per mol RuIII-EDTA complex per hour. An improvement in the rate of ammonia formation (1.67 mol h−1 per mol RuIII-EDTA complex) was observed when the same system was illuminated at the band gap energy of TiO2 (390 nm). A suitable mechanism involving the formation of an intermediate dinitrogen complex of ruthenium(II), (RuII(EDTA)N2−) was proposed for the photoreduction of N2 to NH3.

Nitrosyl ethylenediaminetetraacetato ruthemium(III) — an efficient oxygen atom transfer agent for the oxidation of olefins by molecular O2 and PhIO through ligand-mediated nitrosyl/nitro couple

The complexes [RuIII(EDTA—H)NO]BF4 1 and [RuIII(EDTA)(NO)] 1a were synthesized and characterised by elemental analysis, IR and UV—Vis spectroscopy, conductivity, magnetic susceptibility, EPR and electrochemical studies. Complex 1a catalyses the oxidation by molecular oxygen of 1-hexene to 2-hexanone and cyclohexene to cyclohexene oxide through the ligand-mediated RuIII—EDTA—NO 1a/Ruv—EDTA—NO2 2 oxygen atom transfer. The oxidation reactions were studied in 7:3 ethanol—water medium in the temperature range 30–45 °C (μ=0.1 M KCl). The oxidation of 1-hexene and cyclohexene proceeds with a turnover number of 50 and 44 moles product per mole catalyst per hour. The rate of oxidation is first order with respect to catalyst concentration and one-half order with respect to molecular oxygen concentration. At higher substrate concentrations, the reaction rate was found to be independent of substrate concentration. 18O2 studies indicate that the source of O atom transferred to the substrate is from molecular O2. The formation of an organometallic metallocyclic intermediate is proposed for the reaction. The rate of oxygenation of cyclohexene by iodosyl benzene catalyzed by 1a was found to be identical with that obtained with O2 as oxidant. The rate of oxygenation of 1a to 2 was studied independently by an O atom transfer from iodosyl benzene.

Synthesis, characterization and physicochemical studies of weakly interacting redox-responsive binuclear complexes incorporating ethylenediaminetetraacetatoruthanate(III)

Abstract Novel binuclear complexes of the type [{Ru(edtaH)}2L] [edta- = ethylenediaminetetraacetate, L = pyrazine, 4,4′-bipyridyl, 3,3′-dimethyl-4,4′-bipyridyl, trans-1,2-bis(4-pyridyl)ethylene)] have been synthesized and characterized by physicochemical methods. All the complexes showed weak metal-metal interaction, depending on the nature of the bridging ligand, L. The electrochemical and magnetic susceptibility measurements are consistent with weak interactions between the ruthenium centres.

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.