Abstract: A process is provided for hydrogenating a non-aromatic unsaturated hydrocarbon, comprising reacting the hydrocarbon with a catalyst precursor which includes a source of a group VIIIB transition metal from the second or third rows of the periodic table and a heterobifunctional ligand constructed with a phosphine center and an imine nitrogen center, in the presence of hydrogen and a promoter selected from secondary or tertiary acyclic alkyl amines in a suitable solvent which solubilizes the hydrocarbon, the catalyst precursor, the hydrogen, and the promoter.