<i>Z</i> ‐Selective Semihydrogenation of Internal Alkynes Catalyzed by Phenanthroline‐Based PNNP‐Fe(II) Complexes

Abstract Fe(II) complexes bearing a phenanthroline‐based tetradentate PNNP ligand (2,9‐bis[(diphenylphosphino)methyl]‐1,10‐phenanthroline, 2,9‐bis[(dicyclohexylphosphino)methyl]‐1,10‐phenanthroline) were applied as metal–ligand cooperative catalysts to promote semihydrogenation of internal alkynes. The reaction proceeded with atmospheric H 2 at a catalyst loading of 2–5 mol%/Fe to selectively produce the corresponding Z ‐alkenes. The reactions exhibited good functional group compatibility toward substrates with various substituents, including polar ester and cyano groups, as well as a coordinating sulfur‐containing thiophene moiety.