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.