Highly efficient and selective partial reduction of nitroarenes to N-arylhydroxylamines catalysed by phosphine oxide-decorated polymer immobilized ionic liquid stabilized ruthenium nanoparticles

RuNPs stabilised by a polymer immobilised ionic liquid derived from co-polymerisation of PEG-substituted imidazolium-based styrene monomer and diphenyl(4-vinylphenyl)phosphine oxide, [email protected] = PPh2-PEGPIILS, (2) is remarkably efficient selective catalyst for the hydrazine hydrate-mediated partial reduction nitroarenes to corresponding N-arylhydoxylamine. Near quantitative conversion N-phenylhydroxylamine with > 99 % selectivity was obtained after only 2 h when reaction conducted at 25 °C in ethanol under an inert atmosphere using 0.1 mol% catalyst. Under these conditions, composition-time profile showed that occurred via direct pathway whereas reactions air gave mixture azoxy-based products due competing condensation resulting reversible formation N-phenylhydroxylamine. The initial TOF 6,100 h?1 10 min 40 among highest be reported metal nanoparticle catalysed nitrobenzene significant improvement on 5 wt% Ru/C which modest 21 (initial 240 h?1) aniline. A broad range substituted N-aryl N-heteroaryl were reduced N-arylhydroxylamine high yield excellent adjusting times. However, electron rich amino-substituted extremely slow resulted aniline no evidence hydroxylamine. Complete amino nitroarene proposed facilitated amine-assisted elimination hydroxide hydroxylamine afford readily reducible quinondiimine-derived iminium intermediate reacts surface hydride liberate amine. optimum conditions could reused five times detectable change activity slight decrease selectivity.