Photocatalytic Reduction of Nitrobenzene to Aniline by an Intriguing {Ru(C 6 H 6 )}-Based Heteropolytungstate.

In this paper, we have successfully synthesized a structurally novel heteropolytungstate via coordination of four {Ru(C 6 H 6 )} and trivacant {TeW 9 O 33 } clusters, formulated as Cs 4 Na 2 H 2 [Te 2 W 20 O 72 (H 2 O){(C 6 H 6 )Ru} 4 ]·12H 2 O ( 1 ). Compound 1 inherited the strong absorption of [Ru(C 6 H 6 )Cl 2 ] 2 in the visible region and {TeW 9 O 33 } in the UV region, providing a good basis for photocatalysis. As expected, compound 1 showed good photocatalytic activity in the visible-light-driven reduction of nitrobenzene using N 2 H 4 ·H 2 O as a reductant with a yield of 99.8%, a high turnover number (TON = 330), and a high turnover frequency (TOF = 24 h -1 ). The cyclic experiment of nitrobenzene reduction indicated that compound 1 was an effective and stable heterogeneous catalyst. Finally, the nitrobenzene reduction pathway was affirmed using condensation with azobenzene as a reaction intermediate based on control experiments.