An intriguing tetranuclear Rh-based polyoxometalate for the reduction of nitroarene and oxidation of aniline.

An organic-inorganic hybrid polyoxometalate Na 5 H 5.68 [Na 0.17 Rh 0.83 III (C 6 H 8 N 2 ) 2 Cl 2 ] 2 (C 8 H 8 N 2 ) 2 [As 4 W 40 O 140 Rh 4 IV (C 6 H 4 N 2 S) 2 ]· n H 2 O (1) containing 5.66 Rh atoms is prepared; to our knowledge, it owns the largest number of Rh atoms in the Rh-POM family. Compound 1 demonstrates good catalytic performance in the reduction of nitrobenzene to aniline and the oxidation of aniline to azobenzene under mild conditions. Moreover, catalyst 1 exhibits high activity, excellent stability and recyclability.