Synthesis, characterization, reactivity, and electrochemistry of palladium monolayer protected clusters

This paper describes the synthesis, characterization, reactivity, and electrochemistry of monolayer-protected clusters (MPCs) of palladium that are passivated by monolayers of hexanethiolate or dodecanethiolate ligands. The synthetic product is sensitive to the thiol:Pd ratio used in the reaction mixture: a 1:1 ratio or smaller ratio produces metallic Pd(0) clusters that are similar to analogously prepared Au MPCs, but much more ligand-rich, whereas ≥2:1 ratios yield a very different material that is either extremely small Pd(0) clusters or a form of Pd(II) alkanethiolate complex. The monolayers of the metallic Pd(0) MPCs that are synthesized using small thiol:Pd ratios can be modified by ligand place-exchange and coupling reactions. The electrochemistry of the Pd core and of electroactive labels attached to the alkanethiolate ligands was studied. Quantized double-layer core charging is seen but less clearly than with Au MPCs. The Pd nanoparticles were examined using NMR, FTIR, UV - vis, TEM, TGA, and elemental analysis.