Homogeneous catalysis in water without charged ligands. Reduction of nitrobenzene to aniline by CO/H2O catalysed by [Rh(CO)(4)](-)

We report here that [Rh(CO)(4)](-) (either as a K+, Cs+ or PPN+ salt, PPN+ = (PPh(3)N+) is a very active catalyst for the reduction of nitrobenzene to aniline by CO/H2O in water as solvent. No other ligand, except for CO itself, has to be added. The addition of bases, both inorganic or organic, has a negative effect on the reaction. The experimental conditions have been partly optimised. The reaction is selective for the nitro group.