The structure of two orthorhombic nitroprussides: Cd[Fe(CN)(5)NO]center dot 2H(2)O and Zn[Fe(CN)(5)NO]center dot 2H(2)O

When zinc and cadmium nitroprussides, obtained as powders or single-crystal s samples, are aged in air they lose crystallization water and change their crystalline structure. In the stable form these two complexes are orthorho mbic dihydrates with four molecules in the unit cell. In the aging process the crystals become brittle producing a polycrystalline material. The cryst alline structure of these two complexes (orthorhombic dihydrates) was refin ed from their XRD powder patterns using the Rietveld method. As the startin g model in the refining process the reported orthorhombic structure of copp er nitroprusside (dihydrate) was used. The main changes in the dehydration process associated with the structural transformation take place in the coo rdination sphere of the outer cation (Cd or Zn). (C) 2001 Elsevier Science B.V. All rights reserved.