Synthesis, crystal structure and intermolecular contacts in trans-bis(ethylamine) dichloro platinum(II) and palladium(II) complexes

Abstract

The methods of synthesis of trans-bis(ethylamine)dichloro platinum(II) (trans-[Pt(C2H5NH2)2Cl2]) and palladium(II) (trans-[Pd(C2H5NH2)2Cl2]) complexes for obtaining monophase products were developed. For substance characterizations FTIR spectroscopy, thermogravimetric and X-ray diffraction analysis were used. The crystal structures of the synthesized compounds were determined using X-ray powder diffraction technique. The neutral complexes had specific system of intermolecular contacts in the crystals that allowed distinguishing two forms, A and B. Despite of the similar structure and sizes, trans-[Pt(C2H5NH2)2Cl2] and trans-[Pd(C2H5NH2)2Cl2] complexes created different hydrogen bond networks and crystal structures. The first had a grid topology of 36 with the cells from three and the second - 44 from four complexes. It resulted in different thermal behavior. Trans- [Pt(C2H5NH2)2Cl2]-A demonstrated irreversible solid state transition into B-form at 165 °C and got new H-bond system with the topology similar to the palladium analog (44), however, the realized complex arrangement was significantly different. The structure of B-form was stable until the decomposition at 220°С. High-temperature X-ray diffraction demonstrated high elasticity of the H-bond network in trans-[Pd(C2H5NH2)2Cl2]-A. Notwithstanding significant alterations during heating, the H-bond system returns the structure to its initial state.The interpretation of structural transformation was proposed. The H-bond network formation was influenced by the dynamic properties of the molecules. For the platinum compound, the option with more dense molecular packing occurred. For palladium, the atomic mass distribution was responsible for a larger molecular volume and for a more symmetrical packing. Thermal decomposition of both compounds occurred with simultaneous separation of the halogen and amminoalkyl particles resulting in a low-temperature reduction of the metal and the formation of nanoparticles with sizes in the range of 5–10 nm. For the palladium compound, the decay in vacuum had a noticeable rate already at 100 °C.