Wydział Chemii

Wojciech Zawartka

Andrzej Gniewek

Anna M. Trzeciak

Józef J. Ziółkowski

Juliusz Pernak

2009

Journal of Molecular Catalysis A-Chemical

304

8-15

10.1016/j.molcata.2009.01.011

Naukowa

Angielski

Artykuł

Pd^II anionic, square planar complexes of the type [IL]₂[PdX₄], where IL = imidazolium cations, X = Cl, Br, have been applied for the first time as catalyst precursors for the Suzuki–Miyaura (S–M) reaction carried out in alcohols at 40 °C. Depending on the structure of the catalyst precursor used, different yields of 2-methylbiphenyl (2-MePh–Ph) were obtained in a test reaction of 2-bromotoluene (2-MePhBr) with phenyl boronic acid (PhB(OH)₂). The highest yield, ca. 95%, was obtained for [dmiop]₂[PdCl₄] (dmiop-1,2-dimethyl-3-propoxymethylene imidazolium cation) in methanol in the presence of KOH as a base. It was found that during the reaction Pd⁰ nanoparticles of 4–7 nm have been formed in situ from the palladium(II) precursor. In the first stage of this process, [(IL)₃Pd(OH)₂]⁺-type species have been formed from [IL]₂[PdX₄] precursors. Small Pd⁰ clusters, [(IL)₅Pd₃(H₂O)]⁺ and [(IL)₃Pd₃(H₂O)₇]⁺, were also identified by ESI-MS. These species reacted with ArB(OH)₂ forming palladium aryl complexes of the type [(IL)₂PdAr]⁺, key intermediates in the catalytic process. The first experimental evidence of the IL stabilized Pd⁰ species in S–M reaction is presented.

Palladium complexes, N-Heterocyclic carbenes, palladium nanoparticles, ESI-MS, Suzuki-Miyaura

https://doi.org/10.1016/j.molcata.2009.01.011

http://www.elsevier.com