• KEISHAM S SINGH

      Articles written in Journal of Chemical Sciences

    • Iridium(III) and Rhodium(III) compounds of dipyridyl-N-alkylimine and dipyridyl-NH-ketimine: Spectral characterization and crystal structure

      KEISHAM S SINGH PENG WANG NITEEN A NARKHEDE YURIJ MOZHARIVSKYJ

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      Pentamethylcyclopentadienyl iridium(III) and rhodium(III) complexes of formulation [(η⁵- C₅Me₅)M{(C₅H₄N) ₂C=NR)}Cl]PF₆ were prepared by the reaction of [MCl2(η⁵-C₅Me₅)] ₂ (M = Ir or Rh) with dipyridyl-N-alkylimine ligands, (C₅H₄N) ₂C=NR (R = Me or Et) in the presence of NH₄PF₆ at room temperature. The reaction also produced an unexpected dipyridyl-NH-ketimine organometallic compound

      [(η⁵-C₅Me₅)M {(C₅H₄N) ₂C=NH}Cl]PF6 as minor product when the reaction was performed under refluxing acetonitrile. The NH-ketimine compounds were formed via N-C single bond cleavage of imine ligand resulting in coordination of the transformed ligand, (C5₅H₄N) ₂C=NH to the metal centre. Complexes were obtained as their hexafluorophosphate salts and characterized based on IR, NMR and ESI-MS spectroscopic data. Authenticity of NH-ketimine organometallic compound was established by single crystal X-ray analysis of a representative compound, which crystallized in orthorhombic space group Pbcn and has a pseudo-octahedral geometry around the metal ion.

    • Regioselective synthesis of pyrrole and indole-fused isocoumarins catalysed by N^ O chelate ruthenium(II) complex

      KEISHAM S SINGH SNEHA G SAWANT WERNER KAMINSKY WERNER KAMINSKY

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      Heterocyclic compounds containing pyrrole and indole-fused isocoumarins were obtained from a one-pot synthesis via annulations of N-heterocyclic carboxylic acids and alkynes with N^O chelate ruthenium(II)complex, [RuCl(PySO3)(p-cymene)] (PySO3 = 2-pyridinesulfonate) in the presence of Cu(OAc)2H2O. The reaction proceeds efficiently in DMF but can also be performed in other solvents such as dichloroethane, tAmOH, and water. The annulations reaction is regioselective when performed 1-methylpyrrole-2-carboxylic acid with 1-phenyl-1-propyne.

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