Palladium colloids from an organometallic route: redox reaction between [VCp2] and [(Pd(η3-allyl)2Cl]2. Catalytic application to the hydrogenation of aromatic nitro compounds
Abstract
[Pd(η3-C3H5)2Cl]2 reacts in THF in the presence of poly(vinylpyrrolidone) (PVP), with the 15-electron complex vanadocene [V(C5H5)2], to give PVP-protected palladium particles. High resolution electron microscopy (HREM) and wide angle X-ray scattering (WAXS) experiments were carried out on the PVP-protected palladium particles as obtained when exposed to H2 and O2 and after hydrogenation catalysis. In each case, the particles display the fcc lattice of bulk palladium and a narrow size distribution centred near 2–3 nm. Catalytic hydrogenation reactions of nitrotoluene and 2,4-dinitrotoluene into their corresponding aniline and 2,4-diaminotoluene were performed in CH2Cl2 and in H2O/CH2Cl2 biphasic conditions. The catalytic reactions were found to be zero order with respect to the substrate and first order with respect to dihydrogen and catalyst.