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.