Cobalt-catalyzed (Z)-selective semihydrogenation of alkynes with molecular hydrogen

Cobalt-catalyzed highly (Z)-selective semihydrogenation of alkynes using molecular H-2 was developed using commercially available and cheap cobalt precursors. A variety of (Z)-alkenes were obtained in moderate to excellent selectivities [( Z)-alkene/(E)-alkene/alkane ratio up to >99 : 1 : 1] and it was found that the readily available ethylenediamine ligand is crucial in determining the selectivity.