Carbon-supported NiS catalysts for sustainable transfer-hydrogenation reactions of nitroarenes

We report Ni$_3$S$_2$/C as an effective and environmentally friendly catalyst for the transfer hydrogenation of nitroarenes, using hydrazine monohydrate as a hydrogen donor under mild reaction conditions. The catalyst achieves complete conversion and excellent selectivity across a wide range of nitrobenzene derivatives, bearing both electron-withdrawing and electron-donating groups. Mechanistic studies indicate mainly a direct reduction pathway from nitrobenzene to aniline via nitrosobenzene, unlike Ni/C, which favours a condensation route. The incorporation of sulphur into Ni is shown to tune the selectivity and enhance sulfur tolerance, thereby enabling efficient hydrogenation of nitroarenes containing thiol groups. Moreover, Ni$_3$S$_2$/C is recyclable and effective on a gram-scale reaction, maintaining full conversion and high aniline yields. Compared to conventional noble- and non-noble-metal catalysts that require high-pressure molecular hydrogen, this system offers a cost-effective, robust, and sustainable alternative with strong potential for industrial-scale applications.