The selective semihydrogenation of terminal and internal alkynes was achieved using complexes of the type [(P-P)Ni(eta(2)-C,C-alkyne)] (P-P = chelating diphospine ligands), which behave as the active catalysts and were generated in situ. Boron-hydride derivatives such as ammonia-borane (AB) or sodium boron hydride (SBH) were used as hydrogen sources. In the case of internal alkynes, the stereoselective formation of cis- or trans-alkenes was achieved in high yields and under mild reaction conditions. (c) 2010 Elsevier B.V. All rights reserved.