Substituent effect of diimino-palladium (II) pincer complexes on the catalysis of Sonogashira coupling reaction

Three series 5-Z-2-Br-isophthalaldimines were treated with Pd2(dba)3 to afford the corresponding pincer complexes. Sonogashira coupling demonstrated that the PdII–NCN–NO2 pincers normally exhibited a higher catalytic activity than PdII–NCN–But, PdII–NCN–H pincers. The structural comparison indicated...

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Bibliographic Details
Published inPolyhedron Vol. 96; pp. 107 - 112
Main Authors Zhang, Jin-Hua, Li, Ping, Hu, Wen-Ping, Wang, Hong-Xing
Format Journal Article
LanguageEnglish
Published OXFORD Elsevier Ltd 16.08.2015
Elsevier
Subjects
Chemistry
Chemistry, Inorganic & Nuclear
Crystallography
NCN ligand
NCN pincer complex
Oxidative addition
Palladium
Physical Sciences
Science & Technology
Sonogashira coupling reaction
NCN pincer complex
Oxidative addition
Palladium
Sonogashira coupling reaction
NCN ligand
SUZUKI
PRECATALYSTS
COORDINATION
HECK REACTION
DERIVATIVES
HYBRIDS
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Summary:Three series 5-Z-2-Br-isophthalaldimines were treated with Pd2(dba)3 to afford the corresponding pincer complexes. Sonogashira coupling demonstrated that the PdII–NCN–NO2 pincers normally exhibited a higher catalytic activity than PdII–NCN–But, PdII–NCN–H pincers. The structural comparison indicated that the both the group NO2 at the position-4 of palladium (II) and Me group at the aniline ring might be responsible for the pincers’ high activity, particular for the former dominated. [Display omitted] Three NCN diimine ligands 4–6 were synthesized after condensation of isophthalaldehydes 1–3 and anilines. Treatment of 4–6 with Pd2(dba)3 in toluene resulted in the corresponding PdII–NCN–But (7), PdII–NCN–H (8) and PdII–NCN–NO2 (9) pincer complexes, respectively with high yields. Palladium pincers 7–9 and their precursors 4–6 were fully characterized by elemental analysis, IR, 1H NMR and 13C NMR spectroscopy. The molecular structures of 7b and 9b were also determined by X-ray single crystal diffraction. Sonogashira coupling of phenyl acetylene and 3-nitrobenzene catalyzed by 7–9 show that 9 exhibits the highest catalytic activity, suggesting that the electron withdrawing groups at the position-4 of palladium atom in palladium pincers will enhance their catalytic activity.
ISSN:0277-5387
DOI:10.1016/j.poly.2015.04.031