Selective liquid-phase semihydrogenation of functionalized acetylenes and propargylic alcohols with silica-supported bimetallic palladium-copper catalysts

Silica-supported, bimetallic palladium-copper catalysts were prepared in so lution under mild conditions by reacting lithium di(4-tolyl)cuprate with pa lladium acetate in the presence of silica particles. Small bimetallic palla dium-copper particles were deposited on the silica surface as confirmed wit h TEM-EDAX and EXAFS. The new material has been applied as catalyst in the liquid-phase semihydrogenation of mono- and disubstituted alkynes and showe d high selectivity toward the cis-alkenes. The influence of addition of qui noline or potassium hydroxide to the semihydrogenation reaction mixture and the effects of exposure of the catalyst to air before use have been invest igated.