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Rational Design of Sterically Hindered and Unsymmetrical N py N im O ph Pincer‐Type Ligands and Their Palladium(II) Complexes: Catalytic Applications in Suzuki–Miyaura Reaction and Allylation of Aldehydes
Author(s) -
Maji Ankur,
Singh Ovender,
Rathi Sweety,
Singh U. P.,
Ghosh Kaushik
Publication year - 2019
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201900946
Subject(s) - chemistry , pincer movement , catalysis , palladium , steric effects , phenol , medicinal chemistry , ligand (biochemistry) , coupling reaction , yield (engineering) , proton nmr , stereochemistry , organic chemistry , materials science , biochemistry , receptor , metallurgy
Palladium(II) complexes 1–4 [Pd(L 1 to L 4 )Cl] derived from pincer‐type tridentate ligands having N py N im O ph donors were synthesized from ligands L 1 H to L 4 H (where L 1 H=(2‐phenyl‐2‐(pyridin‐2‐ylmethyl)hydrazono)methyl)phenol, L 2 H =[2‐((2‐phenyl‐2‐(pyridinyl‐2‐ylmethyl) hydrazono) methyl) phenol], L 3 H=[2‐((2‐benzyl‐2‐phenylhydrazono) methyl)‐4,6‐di‐tert‐butylphenol], and L 4 H=[2‐((2‐benzyl‐2‐phenylhydrazono)methyl)‐6‐(tert‐butyl)‐4‐methoxy phenol where H stands for dissociable proton)in quantitative yields. Synthesized ligands L 1 H to L 4 H and corresponding palladium(II) complexes 1–4 were characterized by NMR, IR and HR‐MS spectroscopic studies. Molecular structures of ligand L 4 H and complexes 1 and 3 were determined by X‐ray crystallography. Complexes 1–4 were utilized as catalysts to investigate Suzuki–Miyaura cross‐coupling reaction upon catalyst loading 0.01 mol%. These catalysts also catalysed allylation of aldehydes upto 95% yield upon catalyst loading 0.5 mol% with broad substrate scopes. Theoretical and experimental investigation was performed to speculate reaction pathway of Suzuki–Miyaura cross‐coupling reaction. A reaction model has also proposed for allylation of aldehydes the presence of allyltributylstannane.