Two crystal forms of cis-bis(ethylamine) dichloro platinum(II)

Cis-bis(ethylamine) dichloro platinum(II) (form A) was prepared by a reaction of K2PtCl4 with CH3CH2NH2*HCl and CH3COOK. Form B was obtained from A after recrystallization from a solution of dimethylformamide in HCl. Ab initio crystal structure determination was carried out for both forms using X-ray powder diffraction techniques. The forms A and B are rather similar from the structural point of view. The crystal structures consist of discrete asymmetric molecules with a platinum atom in the planar coordination. Ethyl groups orient towards both sides of the platinum coordination plane. The molecules are packed in layers. Form A differs from B by а smaller cell volume by c.a. 51 Å3. The observed distinction is the result of molecular conformations. IR- and 1H, 13C, 15N MAS NMR spectroscopy’s support the differences in ethylamine conformation for both forms. Thermal decomposition begins for form A at 180 °C whereas for form B it is 10 °C higher, resulting in the formation of Pt metal. The interpretation based on structural features supposes that the acidic media during the recrystallization suppresses hydrogen (Cl···H–N) bonding within cis-[Pt(CH3CH2NH2)2Cl2] molecules and causes more extensive intermolecular H-bonding which results in bigger volume and higher thermal stability.