Thermal and stereochemical studies of some cyclic ligand complexes of palladium(II) in the solid state

Abstract

1,4-Morpholine (morph), 1,4-thioxane (thiox), 1,4-dithiane (dith), N -methylmorpholine (Mmorph) and N , N ′-dimethylpiperazine (DMP) complexes of palladium(II) were synthesized. Thermal investigations have been carried out and the stereochemical changes which occurred during thermal decomposition studied. The complexes were found to have the compositions: [Pd(morph) 2 Cl 2 ], [Pd(thiox) 2 Cl 2 ], [Pd(dith) 2 Cl 2 ], [Pd(Mmorph) 2 Cl 2 ]·2H 2 O, and [Pd(DMP) 2 Cl 2 ]. The characterization and the configurational and conformational changes were studied using elemental and thermal analyses and IR spectral data. All the complexes were found to have square planar structures. Thermodynamic parameters such as activation energy E∗ a , and enthalpy change ΔH were evaluated for the dehydration and decomposition reactions of the complexes using standard methods. The stability of the complexes with respect to activation energy was compared and interpreted in terms of steric and inductive effects.