High-Activity Iron Catalysts for the Hydrogenation of Hindered, Unfunctionalized Alkenes

The activity of aryl-substituted bis­(imino)­pyridine and
bis­(arylimidazol-2-ylidene)­pyridine
iron dinitrogen complexes has been evaluated in a series of catalytic
olefin hydrogenation reactions. In general, more electron-donating
chelates with smaller 2,6-aryl substituents produce more active iron
hydrogenation catalysts. Establishment of this structure–activity
relationship has produced base metal catalysts that exhibit high turnover
frequencies for the hydrogenation of unfunctionalized, tri- and tetrasubstituted
alkenes, one of the most challenging substrate classes for homogeneous
hydrogenation catalysts.