SELECTIVE REDUCTION OF AROMATIC NITRO-COMPOUNDS AFFORDING AROMATIC-AMINES UNDER CO/H2O CONDITIONS CATALYZED BY PHOSPHINE-ADDED RHODIUM AND RUTHENIUM CARBONYL-COMPLEXES

High catalytic activities for the selective reduction of aromatic nitro compounds to the corresponding amines under the mild reaction conditions of room temperature and 1 atm of CO were found to be exhibited by chelatephosphine (dppe, dppm, etc.; dppe: 1,2-bis(diphenylphosphino)ethane, dppm: bis(diphenylphosphino)methane)-added rhodium and ruthenium carbonyl complexes in a 5 N NaOH aqueous solution. The reduction proceeded not only with high catalytic activities, but also with remarkably high nitro group selectivities; for example, 1-nitroanthraquinone afforded 1-aminoanthraquinone without other unsaturated groups (such as C=0) being reduced. PR3-added Rh(CO)2(acac) complexes (PR3: PEtPh2, PEt2Ph, PEt3, etc.; acac: acetylacetonato) in diglyme in a 5 N NaOH aqueous solution were also found to show significant catalytic activities for the reduction of aromatic nitro compounds under mild CO/H2O conditions. Both electronic and steric factors of phosphine ligands are important in making this reaction proceed at such remarkable rates.