Chromium complexes have found very little applications as hydrogenation catalysts. Here, we report a Cr‐catalyzed semi‐hydrogenation of internal alkynes to the corresponding Z‐alkenes with good stereocontrol (up to 99/1 for dialkyl alkynes). The catalyst comprises the commercial reagents chromium(III) acetylacetonate, Cr(acac)3, and diisobutylaluminium hydride, DIBAL−H, in THF. The semi‐hydrogenation operates at mild conditions (1‐5 bar H2, 30 °C).

The hard X-ray spectroscopy methods XAS, valence-to-core XES and higher solution XANES offer unique insights into organometallic reaction mechanisms.