Selective reduction of nitroaromatic compounds via hydrogen transfer, catalyzed by Ir(I) complexes with 2,2'-bipyridine, 1,10-phenanthroline and derivatives

Complexes of the type Irchel(CH2CH2)2Cl and [Ir(chel)hexadiene]-ClO4 (chel = bipyridine, phenanthroline and some of their substituted derivatives) were tested as catalyst precursors in the reduction of aromatic nitro compounds, via hydrogen transfer from propan-2-ol. The influence of the nitrogen-containing chelating ligand, of the anion and of the substrate were examined. At [KOH] /[cat] ratio = 1 the activity of these compounds is clearly higher than those of the ruthenium and rhodium complexes with phosphine, previously proposed as catalysts for this type of reaction. The reduction to amine proceeds by steps, and it is possible to isolate some intermediates in good yields under appropriate experimental conditions.