Palladium(II)/allylpalladium(II) complexes with xanthate ligands: Single-source precursors for the generation of palladium sulfide nanocrystals

In an effort to find simple and common single-source precursors for palladium sulfide nanostructures, palladium(II) complexes, [Pd(S2X)2] (X = COMe (1), COiPr (2)) and η3-allylpalladium complexes with xanthate ligands, [(η3-CH2C(CH3)CR2)Pd(S2X)] (R = H, X = COMe (3); R = H, X = COEt (4); R = H, X = COiPr (5); R = CH3, X = COMe (6)), have been investigated. The crystal structures of [Pd(S2X)2] (X = COMe (1), CoiPr (2)) and [(η3-CH2C(CH3)CH2)Pd(S2COMe)] (3) have been established by single crystal X-ray diffraction analysis. The complexes, 1, 2 and 3 all contain a square planar palladium(II) centre. In the allyl complex 3, this is defined by the two sulfurs of the xanthate and the outer carbons of the 2-methylallyl ligand, while in the complexes, 1 and 2 it is defined by the four sulfur atoms of the xanthate ligand. Thermogravimetric studies have been carried out to evaluate the thermal stability of η3-allylpalladium(II) analogues. The complexes are useful precursors for the growth of nanocrystals of PdS either by furnace decomposition or solvothermolysis in dioctyl ether. The solvothermal decomposition of complexes in dioctyl ether gives a new metastable phase of PdS which can be transformed to the more stable tetragonal phase at 320 °C. The nanocrystals obtained have been characterized by PXRD, SEM, TEM and EDX.