Formation of Pdn(SR)m clusters (n<60) in the reactions of PdCl2 and RSH (R=n-C18H37, n-C12H25)

Mass spectroscopic analysis revealed that Pd clusters passivated by thiolates and the stoichiometric thiolate complexes, Pdn(SR)2n (n=5,6), are formed in the reactions between palladium chloride and n-alkanethiols (RSH: R=n-C18H37, n-C12H25) in toluene. The Pd clusters thus formed are formulated as Pdn(SR)m with m∼0.6n. The cluster sizes, distributed in the range of 5⩽n⩽60, are consistent with their core diameters of ∼1 nm observed by TEM. A gap of ∼2 eV was observed in the optical transition of the Pdn(SR)m clusters showing the emergence of non-metallic properties as a result of size reduction.