Parts-Per-Million of Soluble Pd 0 Catalyze the Semi-Hydrogenation Reaction of Alkynes to Alkenes.

The synthesis of cis -alkenes is industrially carried out by selective semi-hydrogenation of alkynes with complex Pd catalysts, which include the Lindlar catalyst (PdPb on CaCO 3 ) and c-Pd/TiS (colloidal ligand-protected Pd nanoparticles), among others. Here, we show that Pd 0 atoms are generated from primary Pd salts (PdCl 2 , PdSO 4 , Pd(OH) 2 , PdO) with H 2 in alcohol solutions, independently of the alkyne, to catalyze the semi-hydrogenation reaction with extraordinarily high efficiency (up to 735 s -1 ), yield (up to 99%), and selectivity (up to 99%). The easy-to-prepare Pd 0 species hold other potential catalytic applications.