Catalytic hydrogenation of fused heteroaromatic compounds, acridine, quinoline and quinaldine, selectively occurs at the nitrogen containing rings to give 9,10-dihydroacridine, 1,2,3,4-tetrahydroquinoline and 1,2,3,4-tetrahydroquinaldine in the homogeneous solution prepared from the reaction of [Ir(COD)(PPh(3))(PhCN)]ClO4 (COD = 1,5-cyclooctadiene) with H-2 (5 atm) at 50 degrees C, while isoquinoline and indole are not hydrogenated under the same experimental conditions. In the presence of the rhodium analog [Rh(COD)(PPh(3))(PhCN)]ClO4 however, both isoquinoline and indole are also hydrogenated at the nitrogen containing rings, which is understood in terms of heterogeneous catalysis by metallic rhodium powders produced in the reduction of the rhodium compound under the same experimental conditions (50 degrees C, 5 atm of H-2).