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The single crystal and anion structure of Mn[Fe(CN)sNO'2H~_O, obtained by slow interdiffusion of reactant solutions through a TMS gel, was solved by X-ray diffraction methods and refined to RI = 0.036. Spatial group: orthorhombic, Prima, a = 14.069(2), b = 7.538(1), c = 10.543(1),~,, Z = 4. The Mn(ll) ion and the water molecules are sited on mirror planes, which bisect the nitroprusside ions. One of the water molecules is coordinated to Mn(lI) and the other, strongly hydrogen (as acceptor) bonded to the first molecule. The IR spectrum confirms the bonding of the water molecules and TGA results are in accordance with the dihydrate character of the substance and its dehydration in two successive steps. DTA results and the Raman spectrum agree with other results and the comparison between IR and Raman vNO wavenumbers confirms the expected strong vibrational interaction between the closely packed antiparallel (eclipsed) NO groups. There is a topotactic relationship between the dihydrate and the trihydrate, which crystallizes in the space subgroup P2Jn.

The molecular structure of Sr(NH 4 ) 2 [Fe(CN) 6 ]Á 2H 2 O, was determined by X-ray diffraction methods. It crystallizes in the orthorhombic Pnma space group with a = 13.1420(3), b = 14.1656(4), c = 7.3364(2) A ˚, and Z = 4. The structure was solved and refined. The iron(II) complex is located on a crystallographic inversion center with the metal in a nearly perfect octahedral environment [Fe-C bond distances from 1.919(4) to 1.939(4) A ˚]. The Sr(II) ion lies on a crystallographic mirror plane, sandwiched between two nearly square Archimedean anti-prism basis, angled 458 from each other. One base is formed by the two water molecules located on the mirror plane [SrÁÁÁOw distances of 2.741(4) and 2.636(4) A ˚] and by a pair of mirror-related cyanide N-atom [d(SrÁÁÁN) = 2.676(3) A ˚], the other one by two pairs of mirror-related cyanide nitrogen atoms [SrÁÁÁN distances of 2.649(3) and 2.640(4) A ˚] of neighboring [Fe(CN) 6 ] 4anions. The infrared absorption spectrum of the compound was also recorded and briefly discussed.

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