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 CaCO3) and
c-Pd/TiS (colloidal ligand-protected Pd nanoparticles), among others.
Here, we show that Pd0 atoms are generated from primary
Pd salts (PdCl2, PdSO4, Pd(OH)2,
PdO) with H2 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 Pd0 species
hold other potential catalytic applications.