Reaction of the 4-R-benzaldehyde thiosemicarbazones (denoted in general as L-R; R=OCH 3 , CH 3 , H, Cl and NO 2 ) with trans-[Pd(PPh 3 ) 2 Cl 2 ] afforded a group of mixed-ligand complexes (denoted in general as 1-R) incorporating a N,S-coordinated thiosemicarbazone, a triphenylphosphine and a chloride. Similar reaction with Na 2 [PdCl 4 ] afforded a family of bis-thiosemicarbazone complexes (denoted in general as 2-R), where each ligand is N,S-coordinated. Crystal structures of 1-CH 3 , 1-NO 2 , 2-OCH 3 , 2-NO 2 and L-NO 2 have been determined. In all the complexes the thiosemicarbazones are coordinated to the metal center, via dissociation of the acidic proton, as bidentate N,S-donors forming five-membered chelate rings. With reference to the structure of the uncoordinated thiosemicarbazone, this coordination mode is associated with a conformational change around the CN bond. All the 1-R and 2-R complexes display intense absorptions in the visible region. Catalytic activity of the 1-R and 2-R complexes towards some C–C coupling reactions (e.g. Suzuki, Heck and Sonogashira) has been examined and while both are found to be efficient catalysts, 1-R is much better catalyst than 2-R.