Synthesis, structural and theoretical studies of dithiodiglycolamide compounds of palladium(ii)

Abstract

The reaction of palladium(II) halide with dithiodiglycolamide ligands yielded compounds of the type [PdX₂L] (where X = Cl, L = (CH₂SCH₂CONⁱPr₂)₂ (1); L = (CH₂SCH₂CONⁱBu₂)₂ (2); L = (CH₂SCH₂CONBu₂)₂ (3); L = C₇H₆(SCH₂CONⁱBu₂)₂ (4); X = Br, L = (CH₂SCH₂CONⁱBu₂)₂ (5); X = I, L = (CH₂SCH₂CONⁱBu₂)₂ (6)), whereas palladium(II) nitrate yielded compounds of the type [PdL₂](NO₃)₂ (where L = (CH₂SCH₂CONⁱPr₂)₂ (7); L = (CH₂SCH₂CONⁱBu₂)₂ (8)). All compounds were characterized by using IR, ¹H NMR spectral techniques and CHN analyses. The structures of compounds 4, 5 and 7 have been determined by using X-ray diffraction methods. The structures show that the ligands bond through the thioether group to the metal centre in all compounds. They show further that the palladium(II) ion is surrounded by four atoms (two halogens and two thio groups in 4 and 5 and four thio groups in 7) in a square planar arrangement. The dithiodiglycolamide ligand acts as a bidentate chelating ligand and bonds through both the thioether groups to the metal centre, leaving the carbamoyl groups uncoordinated. Theoretical studies reveal that the 1 : 2 compound is energetically more stable and nicely correlates with the IR carbamoyl stretching frequencies as compared to the 1 : 1 compound in which the ligand acts as a tetradentate ligand.