The catalytic performance of small Pd-nanoparticles (NPs) (2.0 nm), partially covered by chemisorbed oxygen atoms, and of Pd-acetate, both stabilized by 2,2'-bipyridine-end functionalized poly(ethyleneglycol) monomethylether was compared in the selective hydration of nitriles to amide in water under mild reaction conditions (353 K). Regardless of the nitrile substrate employed, the Pd-NP-based catalyst showed much higher normalized TON-values (i.e. refereeing to the amount of surface Pd atoms) compared to the Pd(II) macrocomplex, as far as the first catalytic run was considered. Deactivation of the Pd-NP-based catalyst was significant due to the formation of a hydroxide-water layer on the NPs' surface. (C) 2015 Elsevier B.V. All rights reserved.