Microwave Irradiation for the Facile Synthesis of Transition-Metal Nanoparticles (NPs) in Ionic Liquids (ILs) from Metal Carbonyl Precursors and Ru-, Rh-, and Ir-NP/IL Dispersions as Biphasic Liquid Liquid Hydrogenation Nanocatalysts for Cyclohexene

Stable chromium, molybdenum. tungsten. manganese. rhenium. ruthenium, osmium, cobalt, rhodium. and iridium metal nanoparticles (MNPs) have been reproducibly obtained by facile. rapid (3 min), and energy-saving 10 W microwave irradiation (MWI) under an argon atmosphere from their metal carbonyl precursors [M-x(CO)(y)] in the ionic liquid (IL) 1-buty-1-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]) This MWI synthesis is compared to UV-photolytic (1000 W, 15 min) or conventional thermal decomposition (180-250 degrees C. 6-12 h) of M-x(CO)(y)] in ILs The MWI-obtained nanoparticles have a very small (<5 nm) and uniform size and are prepared without any additional stabilizers or capping molecules as long-term stable M-NP/IL dispersions (characterization by transmission electron microscopy (TEM), transmission electron diffraction (TED). and dynamic light scattering (DLS)) The ruthenium, rhodium, or iridium nanoparticle/IL dispersions are highly active and easily recyclable catalysts for the biphasic liquid liquid hydrogenation of cyclohexene to cyclohexane with activities of up to 522 (mol product)(mol Ru)(-1) h(-1) and 884 (mol product) (mol Rh)(-1) h(-1) and give almost quantitative conversion within 2 h at 10 bar H, and 90 C Catalyst poisoning experiments with CS2 (0 05 equiv per Ru) suggest a heterogeneous surface catalysis of RuNPs.