Square-planar 1:2 Ni(II) and Pd(II) complexes with different coordination mode of salicylaldehyde (4)-phenylthiosemicarbazone: Synthesis, structure and spectral properties

Square-planar 1:2 Ni(II) (1) and Pd(II) (2a, 2b) complexes with different coordination mode of salicylaldehyde (4)-phenylthiosemicarbazone (4-PhTSC-salH2) have been synthesized. The molecular and crystal structure for obtained complexes was determined by X-ray crystallography and confirmed by 1H NMR, UV–vis, IR spectroscopy and elemental analysis. It has been shown that one of the 4-PhTSC-salH2 molecules coordinate to the metal ion in tridentate manner in thiolic tautomeric form as a E-isomer; at the same time, another ligand molecule bonded to the metal ion only via thioamide sulphur atom in thion tautomeric form as a Z-isomer. The two polymorphic modifications for the Pd complex with similar molecular, but different crystal structure were obtained and discussed.