A Pd(II) complex of a [beta]-cyclodextrin-based polydentate ligand: an efficient catalyst for the Suzuki reaction in aqueous media

Molecular assembly has become a promising strategy for designing new polydentate ligands. But very often such ligands and their complexes are sparingly soluble in aqueous phase due to their intrinsic hydrophobic character. Pd(II) complexes are good homogeneous catalysts but their poor solubility in...

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Bibliographic Details
Published in:Journal of coordination chemistry 2017-09, Vol.70 (17), p.3035
Main Authors: Das, Ananya, Mishra, Dipu Kumar, Sinha, Dr Biswajit
Format: Article
Language:English
Subjects:
Ambient temperature
Catalysts
Chemical reactions
Choline
Coordination compounds
Coupling (molecular)
Cross coupling
Cyclodextrins
Fourier transforms
Inclusion complexes
Ionic liquids
Ions
Ligands
NMR spectroscopy
Solubility
Spectrophotometry
Stoichiometry
Synthesis
Water reuse
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Summary:Molecular assembly has become a promising strategy for designing new polydentate ligands. But very often such ligands and their complexes are sparingly soluble in aqueous phase due to their intrinsic hydrophobic character. Pd(II) complexes are good homogeneous catalysts but their poor solubility in aqueous phase may limit their catalytic efficacy in the universal green solvent water. However, solubility related challenges especially in aqueous phase can be mitigated through the formation of inclusion complexes by exploiting the hydrophobic nature of the [beta]-cyclodextrin ([beta]-CD) cavity. Hence, an ionic liquid ChCD (1) was synthesized from [beta]-CD and Choline bromide (ChBr). Next a supramolecular N, N[vprime], O-tridentate ligand 1⊂2 (3) was synthesized by the inclusion of 2,6-diaminopyridine (2) in the hydrophobic [beta]-CD cavity of the ionic liquid ChCD (1) and was well characterized by elemental analysis, UV-visible, FTIR, 1H NMR spectroscopy, etc. The stoichiometry of the inclusion complex 1⊂2 (3) was found to be 1:1 based on UV-visible spectrophotometric study. A new air stable, highly water soluble Pd2+-complex [κ3-N, N[vprime], O-Pd(1⊂2)H2O]OAc (4) was then synthesized from the supramolecular ligand (3) with 1:1 stoichiometry and used as a catalyst for Suzuki cross-coupling reactions in water at ambient temperature with good to excellent yields. The catalyst can be removed and recycled. Additionally, the use of non-toxic solvent water makes the methodology green, sustainable, and economically viable.
ISSN:0095-8972
1029-0389
DOI:10.1080/00958972.2017.1378812