[IL]2[PdCl4] complexes (IL = imidazolium cation) as efficient catalysts for Suzuki–Miyaura cross-coupling of aryl bromides and aryl chlorides

Authors:  E. Silarska, A.M. Trzeciak, J. Pernak, A. Skrzypczak

Abstract:
Palladium complexes of the type [IL]₂[PdCl₄] (IL = imidazolium cation) were found to be very active catalysts for the Suzuki–Miyaura reaction of 2-bromotoluene with phenylboronic acid carried out in 2-propanol or 2-propanol/water at 40 ^◦C using normal heating or microwaves as a heating source. In 2-propanol, the highest yields (89% and 85%) were obtained for [dmiop]₂[PdCl₄] and [dmdim][PdCl₄] (dmiop = 1,2-dimethyl-3-propoxymethyl imidazolium cation, dmdim = 3,3'-[1,7-(2,6- dioxaheptane)]bis(1,2-dimethylimidazolium) cation) containing cations substituted at the C₂ carbon with a methyl group. In the presence of water, all [IL]₂[PdCl₄] complexes produced ca. 90% of 2- methylbiphenyl. Very good results were also obtained in the Suzuki–Miyaura reaction of different aryl bromides and chlorides. For example, the conversion of 2-chlorotoluene was 71% at 70^◦C. During the catalytic reaction,the formationof Pd(0)nanoparticles was evidencedby TEM.Mechanistic studies,including Hg(0) tests, showed that Pd(0) nanoparticles acted as a source of catalytically active soluble palladium species.

Keywords:
Palladium
Ionic liquids
Suzuki–Miyaura reaction
Nanoparticles

Published in: Applied catalysis A: General  (Volume 466, Pages 1-314, 10 September 2013)

Publisher: Elsevier  

ISSN Information: 0926-860X

[IL]2[PdCl4] complexes (IL = imidazolium cation) as efficient catalysts for Suzuki–Miyaura cross-coupling of aryl bromides and aryl chlorides

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