Unsaturated hydrogenation, homogeneous catalysis

Rh and Ir complexes stabilized by tertiary (chiral) phosphorus ligands are the most active and the most versatile catalysts. Although standard hydrogenations of olefins, ketones and reductive aminations are best performed using heterogeneous catalysts (see above), homogeneous catalysis becomes the method of choice once selectivity is called for. An example is the chemoselective hydrogenation of a,/ -unsaturated aldehydes which is a severe test for the selectivity of catalysts. 

Hydrogenation reactions are reactions in w hich hydrogen is added to some compound, particularly unsaturated organic compounds. A large number of reactions of this type are of commercial importance, and almost all of them are catalyzed by either a soHd catalyst (heterogeneous catalysis) or some catalyst in solution (homogeneous catalysis). One of the simplest reactions of this type is the hydrogenation of ethylene to produce ethane. 

---