A new organometallic palladium(II) compound derived of 2,6-diacetylpyridine mono(thiosemicarbazone): Synthesis, spectroscopic properties and crystal structure of two solvatomorphic forms

Preparation and characterization of a novel 2,6-diacetylpyridine mono(4-methoxyphenyl-thiosemicarbazone), H2L, is described. Treatment of H2L with PdCl2(PPh3)2 gave the neutral mononuclear complex [PdL(PPh3)]. Both compounds have been characterized by elemental analysis and FAB+ spectrometry and by IR and 1H NMR spectroscopy. Recrystallization of [PdL(PPh3)] in DMSO led to the isolation of two solvatomorphic forms of this compound which were studied by X-ray crystallography. In each solvatomorph, the thiosemicarbazone ligand acts as dianionic [CNS] tridentate donor coordinating to the palladium(II) ion in a square planar geometry through the iminic nitrogen atom, the sulfur atom and one ortho carbon atom of the pyridine ring and the fourth site is occupied by P atom from the PPh3 coligand. The overall molecular conformation of the two solvatomorphs is very similar and the largest difference lies in the orientation of the methyl group of the 4-methoxyphenyl substituent with respect to the sulfur atom.