Recyclable Au Nanoparticle Supported Palladium(II) Catalyst

Key words

gold nanoparticles - cyclotrimerization - palladium(II) catalyst - ionic liquids - microwave

Significance

A gold nanoparticle supported Pd(II) complex was prepared and used in catalytic alkyne cyclotrimeriztion. Thiolate-stabilized Au nanoparticles were treated with dipyridylalkylthiol and the resulting Au-anchored dipyridyl groups coordinated with Pd(II) in a chelating fashion to afford a gold nanoparticle supported Pd(II) complex (RS-Au-Pd). RS-Au-Pd was a highly effective catalyst for the [2+2+2] cyclotrimerization of alkynes under microwave (MW) or thermal conditions to give the corresponding benzenes in 32-99% yield.

Comment

All the microwave-assisted alkyne cyclotrimerization reactions were completed within 1-10 minutes, whereas thermal conditions took 10 minutes to 24 hours under otherwise the same conditions. The catalyst was readily separated and quantitatively recovered from the reaction mixture by simple centrifugation and filtration. The recovered catalyst was reused eight times with slight loss of catalytic activity (cyclotrimerization of 3-hexyne; yield; 1^st use: >99%, 5^th use: 90%, 9^th use: 57%).