New polyaniline/Ni(0) nanocomposites: Synthesis, characterization and evaluation of their catalytic activity in Heck couplings

Development of simple and reliable protocols for the immobilization of catalytically active metal nanoparticles is an important aspect of the nanomaterials field. This paper describes the synthesis and characterization of new organic/inorganic hybrid materials constituted of Ni(0) nanoparticles and polyaniline (PANI). Nanosized Ni(0) particles were prepared by reduction of Ni(OAc)2 using t-BuONa activated sodium hydride in refluxing THF. A ligand exchange with aniline on t-BuONa-stabilized Ni(0) particles yielded aniline-stabilized particles. Ni(0)/PANI nanocomposites were finally obtained by polymerising aniline-stabilized Ni(0) particles by using ammonium persulfate. Samples were characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Results show that this “one-pot” experimental route is successful in producing hybrids constituted of Ni(0) nanoparticles stabilized by PANI due to the strong binding of PANI amine groups to Ni(0) particles. TEM images of the nanohybrids show that metal particles with diameters of ca. 6 nm are homogeneously dispersed on PANI. The catalytic activity of these novel nanocomposites was finally evaluated in Heck reactions. The rate of coupling between aryl iodides and olefins using Ni/PANI catalysts was much higher than those obtained using Ni catalysts reported to date.