Sheo Satish

Metallocene Complexes of Group 4 Elements in the Polymerization of Monoolefins

Abstract Metallocene compounds are becoming an important class of catalyst for the synthesis of organic molecules and polymers [1–6]. These complexes also have good potential to act as catalysts or catalyst precursors for a number of organic reactions [2]. The discovery of Group 4 metallocene-alumoxane systems [7–10] as catalysts for polymerization reactions has opened up a new frontier in the area of organometallic chemistry and polymer synthesis [11–18]. Metallocene systems are comprised of 1) bicomponents consisting of a metallocene and an alumoxane and 2) a single component such as [Cp2MR]+[B(C6F5)4]−. The polymerization of monoolefins by metallocenes in comparison to conventional Ziegler-Natta systems [19–25] offers a versatile possibility to polymer synthesis [26]. The broader flexibility of electronic and steric variations in the cyclopentadienyl (Cp) type ligands allows greater maneuvering in the design of catalyst systems. Such modifications govern the polyinsertion reaction leading to regio- and...

Epoxidation of alkenes with iodosylbenzene using mono-and binuclear Ru(III)-Schiff base complex catalysts

Abstract Mono- and binuclear complexes of Ru(III) were synthesized using Schiff base ligands obtained by condensation of 2-pyridinecarboxaldehyde with 1,2- and 1,3- or 1,4-phenylenediamine, respectively. The complexes were characterized by analytical, spectral, conductance, cyclic voltammetry, and ESR studies. The epoxidation of alkenes was studied using these complexes as catalysts and iodosylbenzene as an oxidant. The complexes were found to be remarkably stable under the reaction conditions. Rates of the epoxidation of cis-cyclooctene using binuclear complexes were found to be nearly twice those using the mononuclear ones, indicating participation of both the metal centres of the former in the reaction. The absence of μ-oxo reaction product was shown by cyclic voltammetric studies. The mechanism of the reaction is suggested.

Arylation of acrylonitrile with iodobenzene over Pd/MgO catalyst

Abstract Heck arylation of acrylonitrile with iodobenzene was studied over different 5% Pd supported catalysts. Among these the activity of the catalysts has the following order: Pd/C

Mixed ligand complexes of chromium(III) and iron(III) : synthesis and evaluation as catalysts for oxidation of olefins

Abstract The mixed ligand complexes Cr III (dpa)(L)Cl and Fe III (dpa)(L)(H 2 O) n Cl (where dpa = dipicolinic acid, l = ethylenediamine, 2,2-bipyridine or 1,10-phenanthroline, n = 1 or 2) were synthesized and characterized by elemental analysis and spectral, magnetic, conductance and electrochemical studies. The complexes were evaluated for their activity as catalysts for the epoxidation of olefins. The chromium complexes catalyzed epoxidation of olefins, viz., norbornene, cis -cyclooctene, styrene and cyclohexene with iodosylbenzene, to give corresponding epoxides. Oxidation of cyclohexene gave allylic oxidation products besides the epoxide. The iron complexes were nearly inactive as epoxidation catalysts under these conditions. Spectrophotometric and electrochemical measurements were used to deduce the cause of low catalytic activity.

Epoxidation of olefins catalysed by Mn(III)-Schiff base complexes

Abstract Mn(III) complexes of Schiff base ligands have been synthesized by the reaction of MnCl 2 ·4H 2 O in ethanolic solutions with the Schiff bases obtained by the condensation of 1,3-diaminopropane or 1,3-diamino-2-hydroxypropane with salicylaldehyde, 2-hydroxynaphthaldehyde or 2-hydroxyacetophenone. The complexes were characterized by elemental analysis, IR spectral, thermogravimetric, conductance, magnetic susceptibility and FAB mass spectral studies. These complexes have been employed as catalysts for the epoxidation of olefins using iodosylbenzene as an oxidant. The efrect of OH substitution on the Schiff base ligand in the complex on its catalytic activity towards epoxidation has been studied.

Oxidation of alkanes by tert-butyl hydroperoxide catalyzed by polynuclear manganese Schiff base complexes

Abstract The polynuclear manganese(III) Schiff base complexes 1 – 7 containing μ -alkoxo and μ -acetato bridging and a variety of structural features were employed as catalysts for oxidation of cyclohexane by tert -butyl hydroperoxide in acetonitrile solution at room temperature. Oxidation of cyclohexane using complexes 1 to 5 gave cyclohexanol and cyclohexanone in moderate to high yields. However, the complexes 6 and 7 possessing chloride ligands, were inactive as catalysts. The complexes 1 and 2 were further employed as catalysts for oxidation of other substrates viz. adamantane, toluene, ethylbenzene, cumene, cis -cyclooctene, trans -stilbene and cyclohexanol. Dual mechanistic pathways involving predominantly a metal based oxidant proceeding in a heterolytic manner and a simultaneous free radical autoxidation are proposed for the oxyfunctionalization of alkanes.

Heterogeneous Pd catalysts and microwave irradiation in heck arylation

Pd metal dispersed on supports like γ-Al2O3, C, MgO and CaCO3 is an efficient and recyclable catalyst in Heck arylation of several olefins. This reaction is also effective in microwave environment.

Oxidation of organic substrates catalysed by mixed ligand RuIII complexes. Investigation of active catalytic species and termination pathway

Abstract The mixed ligand complexes of the type, [Ru III (DPA)(L)Cl] (where DPA=2,6-dipicolinic acid L=ethylenediamine, 2,2′-bipyridine or 1,10-phenanthroline) have been synthesised and characterised by spectral, magnetic and cyclic voltammetric studies. The complexes have been used as catalysts for the oxidation of hydrocarbons using iodosylbenzene and tert -butyl hydroperoxide as the oxidants. The formation of intermediate has been investigated in case of the oxidation reaction involving various oxidants and [Ru III (DPA)(2,2′-bipy)Cl] as a catalyst. It is observed that the same active intermediate, [Ru V (DPA)(2,2′-bipy)(O)], is formed for all of the oxidants. This intermediate catalytically transfers oxygen to the olefin and causes its oxidation. Termination of the catalytic activity is due to the formation of the μ-oxo dimer of the complex, which has been isolated and characterised by elemental analysis, spectral and cyclic voltammetric studies.

Oxyfunctionalization of cyclohexane catalyzed by oxo-bridged manganese Schiff base complexes

Abstract Oxo-bridged polynuclear manganese Schiff base complexes catalyzed the oxidation of cyclohexane to cyclohexanol and cyclohexanone In the presence of tert-butyl hydroperoxide or hydrogen peroxide.

Synthesis of binuclear amide complexes of Ru(III) and study of their catalytic activity in epoxidation of alkenes

Abstract Syntheses of the binuclear amide complexes of Ru(III) are described. The catalytic activity of the complexes, which are highly soluble in water, was examined by carrying out the epoxidations of norbornene, cis -cyclooctene and trans -4-octene to give the respective oxides in the presence of the oxidant iodosylbenzene. The reactions were monitored by UV-Vis and R spectroscopy and cyclic voltammetry, and the reaction mechanism elucidated.