Cobaltocene Reduction of Cu and Ag Salts and Catalytic Behavior of the Nanoparticles Formed

The modes of generation of nanoparticles (NPs) are of great interest for multiple applications in catalysis, optics, sensing, and nanomedicine. Here, fast reduction of CuSO4·5H2O and Ag salts by commercial cobaltocene yields small, stable, water-soluble Cu and Ag NPs with a narrow size distribution without any other ligand or support. The variation of the Ag salt counteranion (NO3–, F–, BF4–) strongly influences both the plasmonic absorption of the AgNPs synthesized in this way and the high apparent rate constant of the AgNP-catalyzed reduction of 4-nitrophenol by NaBH4, showing that the precursor counteranion binds to the AgNP surface. The CuNPs synthesized from CuSO4 and cobaltocene are a recyclable catalyst for the Cu-catalyzed alkyne–azide cycloaddition reaction in water extended to various azides and alkynes, including functionalization of compounds of biomedical interest. Both CuNP and AgNP catalytic activities are also very promising signs for further extension to a variety of other truly efficient...