Browsing by Author "Raj Kumar Sahani"

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A Study on the [3+2] Cycloaddition Reaction of Square Planar Ni(II) Azido Complexes: Structure, Properties, and Catalytic Applications of the Products
(American Chemical Society, 2025) Akash Shrivastav; Raj Kumar Sahani; Subrato Bhattacharya
Two square planar Ni(II) azido complexes [Ni(N3)(L1)] and [Ni(N3)(L2)] (where L1 = N-phenyl-2-(pyridin-2-ylmethylene)hydrazine-1-carbothioamide; L2 = (E)-1-(((2-(diethylamino)ethyl)imino)methyl)naphthalen-2-olato) were used to study the effect of auxiliary ligands on the [3+2] cycloaddition reactions with different dipolarophiles. The reactivity of the complex [Ni(N3)(L1)] was greater than that of the complex [Ni(N3)(L2)]. [Ni(N3)(L1)] gives an N2-triazolato product with an electron-deficient alkyne R1─C≡C─R2 with R1 = R2 = COOCH3, COOEt, or R1 = CF3, R2 = COOEt while [Ni(N3)(L2)] gives a homobimetallic bis(μ-NN’-triazolato) bridged product only with F3C─C≡C─COOEt. The complex [Ni(N3)(L2)] reacts with dialkyl acetylene-dicarboxylate alkyne, yielding N1-triazolato products under strictly anhydrous conditions, whereas the same reaction under ambient conditions yielded a new unexpected octahedral complex in which the alkyne is converted into a novel O, O donor bidentate ligand. The nature of the predominant triazolato isomer (N1/N2) was experimentally confirmed by single-crystal X-ray diffraction analysis and also verified by DFT calculations. [Ni(N3)(L1)] gives a homobimetallic bis(μ-tetrazolato) bridged product by the [3+2] cycloaddition reaction of 2-cyanopyridine and 2-cyanopyrimidine. [Ni(N3)(L1)] also underwent a 1,3-dipolar cycloaddition with phenyl isothiocyanate at room temperature, giving the corresponding tetrazolato-thione complex, while the same reaction with [Ni(N3)(L2)] does not proceed. Both complexes give Ni(II) isothiocyanate complexes by the reaction of carbon disulfide. The catalytic activities of all the Ni(II) complexes were evaluated for the synthesis of 2-amino-3-cyano-4H-pyran derivatives. [Ni(triazolateCOOMe,COOMe-N2)(L1)] (complex 3) emerged as a highly efficient catalyst, demonstrating performance significantly superior to previously reported catalysts at room temperature. 0.0001 mol % catalyst loading is sufficient to obtain the product, and the highest turnover number (680000) and turnover frequency (34000 min-1) were achieved. © 2025 American Chemical Society.
Synthesis and characterization of In(iii) S-thiobenzoylthioglycolate complexes and their catalytic applications in CO2 fixation and multicomponent synthetic reactions
(Royal Society of Chemistry, 2025) Rajesh Pratap; Raj Kumar Sahani; Tarkeshwar Maddeshiya; Himanshu Shekhar Tripathi; Mrituanjay D. Pandey; Subrato Bhattacharya
Indium(iii) complexes of S-thiobenzoylthioglycolate (Stbtg) with nitrogen-donor ligands, such as 2,2′-bipyridyl and 1,10-phenanthroline, have been synthesized. The complexes [In(1,10-phen)(Stbtg)3] (1), [In(2,2′-bipy)(Stbtg)3] (2), and a thioglycolate salt, Na[In(2,2′-bipy)(SCH2COO)2]·H2O (3), obtained by the decomposition of thiobenzoylthioglycolate complexes, were fully characterized using NMR and IR spectroscopy and single-crystal X-ray diffraction. The catalytic activities of these complexes were evaluated for two significant types of reactions. Complex 1 demonstrated exceptional catalytic efficiency in the Knoevenagel condensation and Knoevenagel-initiated multicomponent reactions (MCRs) for the synthesis of 2-amino-4H-chromene derivatives, including cyclohexane-1,3-dione, 5,5-dimethylcyclohexane-1,3-dione, 4-hydroxycoumarin, barbituric acid, and 2-aminobenzimidazole. Additionally, the complexes were found to be highly effective in CO2 fixation reactions, with complex 1 exhibiting the highest activity, followed by 2 and 3. These results highlight the potential of In(iii) complexes as catalysts in a variety of applications, such as organic synthesis and environmentally significant CO2 fixation, demonstrating the broad applicability of non-transition metal complexes in sustainable chemical processes. © 2025 The Royal Society of Chemistry.
Synthesis and structural features of indium(iii) furan-2-thiocarboxylates showing efficient catalytic activity toward multicomponent reactions via Knoevenagel condensation
(Royal Society of Chemistry, 2023) Krishna Kumar; Raj Kumar Sahani; Somenath Garai; Subrato Bhattacharya
A series of furan-2-thiocarboxylate complexes of indium(iii), Et3NH[In(SCOf)4] (1), iPr2NH2[In(SCOf)4] (2), [In(2,2′-bipy)(SCOf)3] (3a), and [In(1,10-phen)(SCOf)3] (3b), have been synthesized and structurally characterized. Complex 4, [In(TMEDA)(SCOf)(SH)2], was obtained by the partial hydrolysis of [In(TMEDA)(SCOf)3] (3). Heterobimetallic complexes [(SCOf)2In(μ-SCOf)2Cu(PPh3)2] (5) and [(SCOf)2In(μ-SCOf)2Ag(PPh3)2] (6), were also synthesized and characterized. In an attempt to synthesize the binary compound, In(SCOf)3 (7), a thioester fCOSCH2SCOf (8) was obtained serendipitously; thus, a novel convenient approach for thioester synthesis is introduced. The catalytic activities of all the complexes were assessed for Knoevenagel condensation and Knoevenagel initiated MCRs for the synthesis of chromene and imidazopyrimidine derivatives and it was found that complex 2 is a very efficient catalyst (much superior to the previously reported ones). © 2023 The Royal Society of Chemistry.