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

[Image: see text] 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.