Browsing by Author "Kumar, L.M."
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Item Air-Stable Cobalt(II) and Nickel(II) Complexes with Schiff Base Ligand for Catalyzing Suzuki Miyaura Cross-Coupling Reaction(2018) Ansari, R.M.; Kumar, L.M.; Bhat, 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 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 Catalytic activity of Fe(II) and Cu(II) PNP pincer complexes for Suzuki coupling reaction(2018) Kumar, L.M.; Ansari, R.M.; Bhat, B.R.Iron and copper PNP pincer complexes of the type [Fe(L)SO4] and [Cu(L)OCOCH3] are reported and represented as C-1 and C-2 catalyst. Both the complexes were synthesized using bis(diphenylphosphino)pyridine-2,6-diamine [L], and salts of Fe and Cu by direct coordination method. The as synthesized complexes were characterized using FTIR, UV Vis, mass analysis and TGA. The effect of reaction time, catalyst load, solvent and base on the reaction between phenylboronic acid and para substituted bromobenzenes in the presence of the catalysts were investigated for evaluating the catalytic efficiency of the complexes. The results obtained highlight the enhanced C-C coupling reactions with the use of 0.4 mol% of the catalyst C-1 in 14 h and 0.6 mol% of C-2 in 16 h respectively with Cs2CO3 base and ACN as solvent media. Of the two complexes reported, C-1 with iron as catalytically active metal is more stable and active towards coupling which is reflected in its better coupling yields in lesser reaction time compared to copper bearing C-2 complex. Copyright 2017 John Wiley & Sons, Ltd.Item Catalytic activity of Fe(II) and Cu(II) PNP pincer complexes for Suzuki coupling reaction(John Wiley and Sons Ltd, 2018) Kumar, L.M.; Ansari, R.M.; Badekai Ramachandra, B.R.Iron and copper PNP pincer complexes of the type [Fe(L)SO4] and [Cu(L)OCOCH3] are reported and represented as C-1 and C-2 catalyst. Both the complexes were synthesized using bis(diphenylphosphino)pyridine-2,6-diamine [L], and salts of ‘Fe’ and ‘Cu’ by direct coordination method. The as synthesized complexes were characterized using FTIR, UV–Vis, mass analysis and TGA. The effect of reaction time, catalyst load, solvent and base on the reaction between phenylboronic acid and para substituted bromobenzenes in the presence of the catalysts were investigated for evaluating the catalytic efficiency of the complexes. The results obtained highlight the enhanced C-C coupling reactions with the use of 0.4 mol% of the catalyst C-1 in 14 h and 0.6 mol% of C-2 in 16 h respectively with Cs2CO3 base and ACN as solvent media. Of the two complexes reported, C-1 with iron as catalytically active metal is more stable and active towards coupling which is reflected in its better coupling yields in lesser reaction time compared to copper bearing C-2 complex. © © 2017 John Wiley & Sons, Ltd.Item Cobalt pincer complex catalyzed Suzuki-Miyaura cross coupling A green approach(2017) Kumar, L.M.; Bhat, B.R.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 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 Corrigendum to “Iron pincer complex and its graphene oxide composite as catalysts for Suzuki coupling reaction†(Journal of Saudi Chemical Society (2019) 23(3) (307–314), (S1319610318300905), (10.1016/j.jscs.2018.08.005))(Elsevier B.V., 2019) Kumar, L.M.; Mishra, P.; Badekai Ramachandra, B.R.The authors regret to inform that the Scheme 1 of the aforementioned article was incorrect as, wherein, the FNAGO complex formed seems to have an amide bond with the metal centre of the Fe-NCN complex instead of the actual amine bond with the metal. The correct Scheme 1 is provided below: The authors would like to apologise for any inconvenience caused. © 2019 King Saud UniversityItem Fe PNP Pincer Complex Immobilized on Graphene Oxide as a Catalyst for Suzuki Miyaura Coupling Reactions(2019) Kumar, L.M.; Mishra, P.; Bhat, B.R.Fe PNP pincer complexes are the upcoming homogenous catalyst for organic reactions to overcome the need of much expensive Pd based catalysts. However, the lack of recovery and reusability are two significant challenges for homogeneous catalysts. We report herein a Fe PNP complex immobilized on graphene oxide as a heterogeneous catalyst for the Suzuki coupling reactions. The prepared composite showed remarkable conversion efficiency towards Suzuki coupling reaction between phenylboronic acid and aryl halides. The study also discusses the parameters that are affecting the coupling reaction. The proposed catalyst can be quickly recovered and reused without any significant reduction in performance. Graphical Abstract: [Figure not available: see fulltext.]. 2019, Springer Science+Business Media, LLC, part of Springer Nature.Item Fe–PNP Pincer Complex Immobilized on Graphene Oxide as a Catalyst for Suzuki–Miyaura Coupling Reactions(Springer Science and Business Media, LLC, 2019) Kumar, L.M.; Mishra, P.; Badekai Ramachandra, B.R.Fe–PNP pincer complexes are the upcoming homogenous catalyst for organic reactions to overcome the need of much expensive Pd based catalysts. However, the lack of recovery and reusability are two significant challenges for homogeneous catalysts. We report herein a Fe–PNP complex immobilized on graphene oxide as a heterogeneous catalyst for the Suzuki coupling reactions. The prepared composite showed remarkable conversion efficiency towards Suzuki coupling reaction between phenylboronic acid and aryl halides. The study also discusses the parameters that are affecting the coupling reaction. The proposed catalyst can be quickly recovered and reused without any significant reduction in performance. Graphical Abstract: [Figure not available: see fulltext.]. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.Item Iron pincer complex and its graphene oxide composite as catalysts for Suzuki coupling reaction(2019) Kumar, L.M.; Mishra, P.; Bhat, 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 UniversityItem 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 UniversityItem 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 Retraction Note to: Fe–PNP Pincer Complex Immobilized on Graphene Oxide as a Catalyst for Suzuki–Miyaura Coupling Reactions (Catalysis Letters, (2019), 149, 4, (1118-1124), 10.1007/s10562-019-02652-7)(Springer, 2021) Kumar, L.M.; Mishra, P.; Badekai Ramachandra, B.R.The Editors have retracted this article [1]. Since publication, the article [2] that served as a basis for the synthesis of the Fe–PNP pincer complex has been retracted [3] due to the findings not being reproducible. The results of this article [1] are therefore unreliable. P.M. agrees with the retraction. B.R.B. does not agree with the retraction. L.M.K. has not responded to any correspondence from the Publisher regarding this retraction. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.