Novel Pd(II) coordination compounds involving 2-[(2-hydroxyphenyl)methylene]hydrazine-N-(2-propenyl)-carbothioamide as a ligand or pro-ligand: Synthesis, crystal structures and analytical application

Abstract Novel palladium(II) complexes with a thiourea derivative 2-[(2-hydroxyphenyl)methylene]hydrazine- N -(2-propenyl)-carbothioamide have been synthesized and characterized by single crystal X-ray diffraction, IR, UV–Vis, 1 H and 13 C NMR spectroscopy. Depending on synthesis conditions the ligand could be coordinated to the metal ion as a neutral molecule or mono-/bianion forming complexes Pd(H 2 L)Cl (I), Pd(HL)H 3 L (II), Pd(HL′)Cl (III). The different coordination of two ligand molecules realize in the complex ( II ), where one carbothioamide molecule coordinates in a tridentate manner being in the thiol form and another one binds to the metal by the sulfur of the thioureide group in a monodentate manner being in the thione tautomeric form. The compound ( III ) is synthesized in the acidic medium that causes the cyclization of the allyl fragment of carbothioamide. The selected ligand also reacts with Pd(II) as a dibasic acid to yield an anionic complex [Pd(HL)Cl] − , which is isolated as a salt of the astraphloxin basic dye, [Pd(HL)Cl][AF]. The last one is used for developing a procedure for selective extraction of Pd 2+ from aqueous solutions containing a mixture of platinum metals.