Browsing by Author "Ramananda Maity"

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A naphthalene-based heterobimetallic triazolylidene IrIII/PdII complex: regioselective to regiospecific C-H activation, tandem catalysis and a copper-free Sonogashira reaction
(Royal Society of Chemistry, 2023) Adhir Majumder; Rajat Naskar; Pallabi Roy; Bhaskar Mondal; Somenath Garai; Ramananda Maity
Heterobimetallic complexes featuring mesoionic carbene (MIC) donor ligands are gaining enormous popularity in tandem catalysis owing to the combined action of two different metal centers during catalysis. A rare version of the heterobimetallic PdII/IrIII complex possessing a cyclometalated mesoionic carbene (MIC) ligand is presented along with the analogous homodinuclear PdII complex. A sterically controlled regiospecific cyclometalation towards the formation of a six-membered ring complex over a five-membered ring complex has been performed using a naphthalene-based bis-MIC ligand platform. The interplay between regioselective vs. regiospecific C-H bond activation for the synthesis of cyclometalated IrIII complexes has also been demonstrated using the corresponding naphthyl-derived mono-imidazolylidene ligand. Both homodinuclear PdII and heterobimetallic PdII/IrIII complexes have been characterized using standard spectroscopic techniques including 1H, 13C{1H}, 2D correlation NMR spectroscopy and ESI mass spectrometry. The structure of the cyclometalated heterobimetallic complex has been established by single crystal XRD. The heterobimetallic complex has been employed as a pre-catalyst in the tandem Suzuki-Miyaura/transfer hydrogenation reaction and the homobimetallic PdII complex has been successfully employed as a catalyst in both the Sonogashira coupling and α-arylation of 1-methyl-2-oxindole. © 2023 The Royal Society of Chemistry.
Bimetallic PdII complexes with NHC/Py/PCy3 donor set ligands: applications in α-arylation, Suzuki-Miyaura and Sonogashira coupling reactions
(Royal Society of Chemistry, 2022) Adhir Majumder; Rajat Naskar; Shankab J. Phukan; Ramananda Maity
Bimetallic complexes bearing NHC donor ligands are gaining immense popularity as catalysts in organometallic chemistry. However, such complexes with a mixed NHC/PR3 donor set ligands are still rare. We present here a series of bimetallic PdII complexes featuring mixed NHC/Py/PCy3 donor set ligands applied in α-arylation of amide, Suzuki-Miyaura coupling and Sonogashira coupling reactions. All complexes have been characterized using standard characterization techniques and one of the complexes has been structurally characterized by X-ray crystallographic analysis. Catalytic outcomes clearly indicate the superior activity of PdII complex bearing mixed NHC/PCy3 donor set ligands compared to the PEPPSI-type complexes in both α-arylation of amide and Sonogashira coupling reactions, though almost similar activities were observed for all the complexes in Suzuki-Miyaura coupling reactions. This observation might be due to the involvement of Pd-NPs as an active catalyst in Suzuki-Miyaura coupling reactions, whereas the Hg-poison test suggested the homogeneous nature of the other two types of reactions. Two pyridine rings in a mixed NHC/4-OMe(Py) donor complex are oriented almost in a parallel face-to-face fashion with a centroid to centroid separation of 3.758 Å, indicating π···π interactions between two methoxypyridine rings. This interaction leads to a very short Pd···Pd distance of 5.754 Å in the aforementioned complex. © 2022 The Royal Society of Chemistry
Dinuclear platinum(ii) complexes with biphenyl-based bis-carbene ligands
(Royal Society of Chemistry, 2024) Rajat Naskar; Bhaskar Mondal; Diya Sengupta; Aninda Ghosh; Somenath Garai; Ramananda Maity
Multimetallic NHC (N-heterocyclic carbene) complexes comprising platinum(ii) centers are rare. Four new dinuclear platinum(ii) complexes possessing a combination of NHC and Py/4-Cl(Py) ligands are presented. Both classical and mesoionic carbene (MIC) ligands have been employed for the complexation. All complexes have been characterized using standard spectroscopic tools. The coordination of both classical NHC and pyridine ligands around the platinum(ii) center in complex [2] has been established by using single crystal XRD. © 2024 The Royal Society of Chemistry.
Tetranuclear PdII Complexes Containing an Adamantane-Based Tetra-MIC Ligand: Ancillary-Ligand-Dependent Catalytic and Redox Activities
(American Chemical Society, 2024) Bhaskar Mondal; Rajat Naskar; Jayanta Bag; Somenath Garai; Ramananda Maity
The novel tetra-triazolium salt 1, featuring a tetrasubstituted central adamantane backbone, is introduced for the synthesis of tetranuclear PdII MIC complexes by quadruple C5-H deprotonation and subsequent addition of the corresponding PdII precursors. The three newly prepared palladium(II) complexes appeared to be stable and have been characterized using standard spectroscopic and HRMS techniques. The molecular structure of the tetranuclear PdII complex bearing a 4-methoxypyridine ligand has been established by using single-crystal XRD. All three newly prepared tetranuclear PdII complexes appeared as active precatalysts for the Sonogashira coupling reaction, which occurred in a homogeneous fashion; however, only the palladium(II) complex bearing a combination of MIC and phosphine ligands was found to be active for the intermolecular α-arylation of 1-methyl-2-oxindole, as the complexes bearing a pyridine or a 4-methoxypyridine ligand decomposed to Pd0 NPs and appeared to be inactive in the α-arylation reaction. The ancillary-ligand-dependent (Py vs PPh3) interplay between homogeneous and heterogeneous catalyses has also been correlated with the catalytic outcomes in α-arylation of 1-methyl-2-oxindole. The electrochemical responses of these complexes have been measured, and the effect of ancillary ligands in both electrochemistry and catalysis has also been examined. © 2024 American Chemical Society.