Faculty Publications
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Item Cobalt pincer complex catalyzed Suzuki-Miyaura cross coupling – A green approach(Elsevier B.V., 2017) Kumar, L.M.; Badekai Ramachandra, B.A series of cobalt complexes with tridentate pincer ligands were synthesized to study their catalytic activity in Suzuki-Miyaura coupling reactions. Cobalt complexes, C-1, C-2, C-3 bearing asymmetrical PNCOP pincer ligand [C6H4-1-(NHPPh2)-3-(OPPh2)] (L-1) and symmetrical PNCNP, PNNNP pincer ligands [C6H4-2,6-(NHPPh2)2] (L-2) and [C5H3N-2,6-(NHPPh2)2] (L-3) were synthesized by the reaction of diphenylchlorophosphine with m-aminophenol, m-phenylenediamine and 2,6-diaminopyridine respectively in a 1:2 ratio in the presence of triethylamine as a base and tetrahydrofuran as solvent media. The synthesized complexes were examined for their C-C coupling efficiency in cross-coupling between phenyl boronic acid and para substituted bromobenzenes. Effect of variation of the ligand on the catalytic activity of cobalt pincer complex was explored based on the coupling yields. It is observed that as the number of ‘N’ atoms increases in the side arm of the ligand, the donating ability of the ligand increases which leads to the increased catalytic activity of the complex. The symmetrical PNNNP pincer complex (C-3) was found to be more effective as a catalyst among the complexes synthesized and reported in the present study. © 2016 Elsevier B.V.Item Air-Stable Cobalt(II) and Nickel(II) Complexes with Schiff Base Ligand for Catalyzing Suzuki–Miyaura Cross-Coupling Reaction(Pleiades journals, 2018) Ansari, R.M.; Kumar, L.M.; Badekai Ramachandra, B.R.The Co(II) complex [Co{C6H4–1,2-(N=CH–C6H4O)2}] (I) and Ni(II) complex [Ni{C6H4–1,2-(N=CH–C6H4O)2}] (II) with Schiff base of o-phenylenediamine and salicylaldehyde have been synthesized. The structure of the ligand and its complexes were derived on the basis of various techniques such as elemental analysis, mass, FT-IR, electronic spectra and magnetic susceptibility. From the Singal crystal X-ray diffraction (SCXRD) analysis techniques (CIF file CCDC no. 1498772 (II)), it has been confirmed that the Schiff base ligand (L), coordinates to the metal ion in a tetradentate fashion through the nitrogen and oxygen atom. In addition, the square planar geometry of Ni(II) complex also has been confirmed from SCXRD. Electronic spectra, mass spectra, and magnetic susceptibility measurements reveal square planar geometry for the Co(II) complex. Synthesized complexes were used in cross-coupling of arylhalides with phenylboronic acid. The transformation offers products in good yields using 0.02 mmol catalysts loading, thereby proving the efficiency of the complexes as catalysts for Suzuki–Miyaura reaction. © 2018, Pleiades Publishing, Ltd.Item Iron Pincer complexes as catalysts in cross-coupling of aryl halides and phenylboronic acid(Science Publishing Corporation Inc ijet@sciencepubco.com, 2018) Kumar, L.M.; Badekai Ramachandra, B.R.Pincer complexes with iron as active metal center were synthesized to study their catalytic activity in Suzuki-Miyaura coupling reactions. Tridentate pincer ligand was synthesized by the reaction of diphenylchlorophosphine with m-aminophenol and m-phenylenediamine respectively in a 2:1 ratio in the presence of triethylamine as a base and tetrahydrofuran as solvent media. The resultant ligand was complexed with FeSO4 to obtain PCP complexes, C-1 with O and N atoms in the side arms and C-2 with both N atoms in the side arms. The synthesized complexes were examined for their C-C coupling efficiency in cross-coupling between phenyl boronic acid and para substituted halobenzenes. The research study aims to provide an alternative approach to the Pd catalyzed cross coupling methods, an otherwise subjugated method to obtain cross-coupled products. Also the study implores on the effect of variation in the side arm atom relating to the donating ability of the ligand and thereby relatively affecting the coupling yield of the catalysts. © 2018 Authors.Item Iron pincer complex and its graphene oxide composite as catalysts for Suzuki coupling reaction(Elsevier B.V., 2019) Kumar, L.M.; Mishra, P.; Badekai Ramachandra, B.R.We report the synthesis of Fe-NCN pincer complex as homogenous catalyst and its composite by immobilizing the complex on amino functionalized graphene oxide as a heterogeneous catalyst for Suzuki coupling reactions. Both the complex and the composite were employed in catalyzing the Suzuki-Miyaura cross-coupling reaction between the aryl halide and phenyl boronic acid in acetonitrile solvent media with Cs2CO3 as a base. Effect of substitution over aryl halide was also investigated. Immobilization of the pincer complex had advantageous recovery and reuse of the catalyst as compared to its homogenous analog with no significant decrease in the catalytic efficiency. © 2018 King Saud University