Palladium and Bimetallic Palladium–Nickel Nanoparticles Supported on Multiwalled Carbon Nanotubes: Application to CarbonCarbon Bond‐Forming Reactions in Water

Palladium and bimetallic Pd–Ni nanoparticles (NPs) protected by polyvinylpyrrolidone were prepared by the reduction‐by‐solvent method and deposited on multiwalled carbon nanotubes (MWCNTs). The catalytic activity of these NPs to carbon–carbon bond‐forming reactions was studied by using 0.1 mol % Pd loading, at 120 °C for 1 h and water as a solvent under ligand‐free conditions. The Suzuki–Miyaura reaction took place quantitatively for the cross‐coupling of 4‐bromoanisole with phenylboronic acid, better than those obtained with potassium phenyltrifluoroborate, with Pd 50 Ni 50 /MWCNTs as a catalyst and K 2 CO 3 as a base and TBAB as an additive, with good recyclability during 4 cycles with some Ni leaching. The Hiyama reaction of 4‐iodoanisole with trimethoxyphenylsilane, under fluoride‐free conditions using 50 % aqueous NaOH solution, was performed with Pd/MWCNTs as a catalyst in 83 % yield with low recyclability. For the Mizoroki‐Heck reaction 4‐iodoanisole and styrene gave the corresponding 4‐methoxystilbene quantitatively with Pd 50 Ni 50 /MWCNTs using K 2 CO 3 as a base and TBAB as an additive although the recycle failed. In the case of the Sonogashira‐Hagihara reaction, Pd/MWCNTs had to be used as a catalyst and pyrrolidine as a base for the coupling of 4‐iodoanisole with phenylacetylene under copper‐free conditions. The corresponding 4‐methoxytolane was quantitatively obtained allowing the recycling of the catalyst during 3 cycles.