The structure of two orthorhombic nitroprussides: Cd[Fe(CN)_5NO]·2H_2O and Zn[Fe(CN)_5NO]·2H_2O

摘要

When zinc and cadmium nitroprussides, obtained as powders or single-crsytals samples, are aged in air they lose crystallization water and change their crystalline structure. In the stable form these two complexes are orthorhombic dihydrates with four molecules in the unit cell. In the aging process the crystals become brittle producing a polycrystalline material. The crystalline structure of these two complexes (orthorhombic dihydrates) was refined form their XRD powder patterns using the Rietveld method. As the starting model in the refining process the reported orthorhombic structure of copper nitroprusside (dihydrate) was used. The main changes in the dehydration process asociated with the structural transformation take palce in the coordination sphere of the outer cation (Cd or Zn).